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Cold War Brazilian Armor

EE-9 M1 Cascavel

https://www.tanks-encyclopedia.com/images/drapeaux/brazil_r.jpg Brazil (1971-1975/1976)
Reconnaissance Vehicle – Atleast 9 built, up to a hundred ordered excluding prototypes

Up until 1967, Brazil was dependent on foreign countries for armored vehicles. Throughout and in the aftermath of World War 2, Brazil received large numbers of cheap surplus armored vehicles from the United States, including the M3 Stuart and the M4 Sherman, as it had entered the war on the Allied’s side in 1942. In fact, Brazil had not undertaken any tank design since 1932, and those had only been conversions of tractors and cars into armored vehicles during the revolutions of 1924, 1930, and 1932.

Between 1932 and 1958, the Brazilian Armed Forces created a solid basis of technical institutes from which it could educate technical and research personnel. In turn, these helped the Brazilian automotive industry in developing its own automotive parts and helped in opening laboratories for the manufacturers. In 1967, Brazil set up a plan for the country to become more militarily self-sustaining. The flow of US material had decreased because of its entanglement in the Vietnam War and, after a study, Brazil recognized external dependence on arms suppliers as a serious problem for its political position in South America.

The plan to solve this became the start of the Brazilian defense industry. After the Army had remotorised various vehicles, such as the M8 Greyhound, with diesel engines, they set off developing Brazil’s first wheeled vehicle with serial production in mind. The 4 x 4 VBB-1 that resulted from this development was everything but revolutionary. It did provide the needed experience and confidence for the Brazilian engineers though. With the rejection of the VBB-1 because the Army wanted a 6 x 6 vehicle, Brazilian engineers started developing the vehicle which would become the most successful armored fighting vehicle Brazil ever developed: the EE-9 Cascavel.

An EE-9 M1.
Source: https://webkits.hoop.la/topic/procurando-imagens-do-ee-9-cascavel-magro?reply=471368445555157354

Genesis

The story of why the EE-9 Cascavel (English: Rattlesnake) was developed can be traced back to the Second World War. Brazil sent an expeditionary force, known as the Smoking Snakes, to fight in Italy alongside the Allies. During the Italian Campaign, the Brazilian forces were armed with US M8 Greyhounds. The M8 Greyhound turned into the most loved vehicle by the Brazilian soldiers, and after WW2, this love would remain embedded in the Brazilian Army. The positive experience with the M8 during WW2 caused it to be the most impactful vehicle for the Brazilian development of armored vehicles. As a result, most of the wheeled vehicles and the wheeled vehicle program can trace back their roots to the M8 Greyhound during the Italian campaign. This love for the M8 resulted in the development of Brazil’s EE-9 Cascavel some 25 years after WW2, a heavily improved and altered concept of the M8 Greyhound.

Soldiers of the Brazilian Força Expedicionária Brasileira (FEB) in Italy.
Source: https://tecnodefesa.com.br/75-anos-do-dia-da-vitoria-ordem-do-dia/

Although Brazil enjoyed its diplomatic relations with the United States well into the 1970s, the first steps to break free from the United States, from an Army materiel point of view, started in 1967. The United States got increasingly involved with the Vietnam War and, as a result, could not supply Brazil with the cheap equipment it once did. This severely undermined Brazil’s political power in South America. Not only were they seen as a United States proxy state, now with the military ties effectively cut loose, Brazil had no way to fight a prolonged war with its neighbors.

The Brazilian Army conducted a study regarding its dependency on the United States in 1967, which resulted in the Triennial Plan 68/70. The Brazilian Army recognized its external dependence as a serious issue and advocated for the encouragement of R&D (Research and Development) of locally designed and produced materiel. This would in turn cause the Diretoria General de Material Bélico (DGMB) (English: General Directorate of War Material) to further study armored equipment from all over the globe, with 4 x 4 and 6 x 6 vehicles in particular. By studying the wheeled vehicles of the United States, the United Kingdom, Belgium, Switzerland, the Netherlands, and Italy at the time, the DGMB called for the intensive adoption of wheeled armored vehicles. These vehicles required a relatively modest investment for their development, and as such, were more viable to develop instead of importing them. The study proposed the creation and adoption of a vehicle like the M8 Greyhound, but simpler.

PqRMM/2

From this point onward, the Parque Regional de Motomecanização da 2a Região Militar (PqRMM/2) (English: Regional Motomecanization Park of the 2nd Military Region) started taking the first steps towards developing armored vehicles for the Army. The PqRMM/2 was a group of army automotive engineers gathered to study, develop and produce armored vehicles in Brazil, and were the pioneers of the Brazilian defense industry.

The first step the PqRMM/2 team undertook was the motorization of Brazil’s M8 Greyhounds and M2 half-tracks with locally produced diesel engines. With the success of these projects, they continued to the next phase of the program and developed Brazil’s first wheeled vehicle with serial production in mind. The Viatura Blindada Brasileira 1 (VBB-1) (English: Armored Car of Brazil 1) was a 4 x 4 vehicle meant for reconnaissance and mounted a copy of the M8 Greyhound turret. The VBB-1’s concept came from the Belgian FN 4RM 62F, but its design was based on the M8 Greyhound. Although the VBB-1 seems to have successfully performed its tests when the vehicle was presented to the Army in 1969, the Army did not want a 4 x 4. It was briefly considered by the engineers to cut the hull in half and lengthen it to accommodate a 6 x 6 suspension, but the idea was almost immediately rejected, as the development of a new vehicle was deemed more effective.

Why the PqRMM/2 engineers developed a 4 x 4 for the Army in the first place is a bit strange, considering they knew that the army wanted a 6 x 6 like the M8 Greyhound. Nevertheless, the VBB-1 would lay the groundwork for the research of the 6 x 6 vehicle. Some components were carried over from the VBB-1 to the upcoming 6 x 6, such as the turret and engine. By starting from scratch, the team could implement all the lessons they learned from the VBB-1 project and thus get a better basis for future developments.

The VBB-1, note the influence of the M8 Greyhound like the turret..
Source: Blindados no Brasil

The VBR-2

For the development of the Viatura Blindada de Reconhecimento 2 (VBR-2) (English: Armored Reconnaissance Vehicle), the PqRMM/2 team followed the specifications of the Diretoria de Motomecanização (DM) (English: Directorate of Motomechanisation). The VBR-2 was pretty much a Brazilian copy of the M8 Greyhound. A single metal mock-up of the VBR-2 was made by the PqRMM/2 in early 1970.

Its overall shape was almost identical to the M8, with the raised hull construction for the driver being one of the most notable features. The hull construction was a bit more simplified though, with more flat plates like the VBB-1, but without some of the complicated shapes of the VBB-1. It mounted the same turret as the VBB-1, which was a copied M8 Greyhound turret but with a closed top. It was armed with a 37 mm cannon and a .50 cal machine gun.

The engine deck style also resembled the M8’s and came from the VBB-1 design as well. Considering the overall design features, it can be expected that the rear of the VBR-2 would also look like the M8, considering the VBB-1 and the later EE-9 Cascavel rear all share the same design.

VBR-2, note the VBB-1 turret and its overall blocky design, the VBR-2.
Source: https://www.cibld.eb.mil.br/index.php/historico-2/blindados-eb-parte-3

The CRR

The VBR-2 mock-up underwent various redesigns together with a redesignation to Carro de Reconhecimento sobre Rodas (CRR) (English: Wheeled Reconnaissance vehicle). The hull underwent some geometric redesigning, causing the vehicle to look less like a box because of the more angled side plates. Another difference in the hull design, which enabled the hull to receive an improved ergonomic design, was the redesign of the driver’s raised hull construction.

The VBR-2 had a raised construction that extended towards both sides of the hull to provide vision for both the driver and co-driver much like the M8 Greyhound. The raised hull construction was now located in the middle of the hull on the CRR and did not extend to both sides of the hull. This meant that the CRR did not have a co-driver, which reduced the crew to 3.

Another important step in the development of the CRR was the installation of the Boomerang suspension from Engenheiros Especializados SA, better known as Engesa. Engesa had previously modernized and delivered new trucks for the Brazilian Army with their Total Traction system. This patented traction system was the key for Engesa in the defense industry, mainly because it was identified as a system ‘of interest to National Security’ by the Army. Engesa also participated in the VBB-1 project by supplying the transfer box. With the VBR-2 built, the PqRMM/2 team sought a better suspension system for the 6 x 6 vehicle and found it in an invention from 1969.

The CRR during construction.
Source: Ford M-8 Greyhound no Exército Brasileiro – Expedito Carlos Stephani Bastos

The Boomerang Suspension

In 1969, Engesa invented the Boomerang suspension. The suspension was invented to enable trucks to transport oil from difficult terrain with bad infrastructure to the refineries. With this suspension, the trucks could traverse otherwise untraversable hills for conventional suspension systems, as the wheels would always stay in contact with the ground to provide maximum traction.

An EE-9 M2 showing the boomerang suspension.
Source: Engesa Brochure

The suspension system was a two wheeled-single axle driven suspension. The advantage of the boomerang suspension was that it could be fitted on existing differentials with a single axle. Normally, this meant that the single axle, designed for the torsion forces of a single wheel, was subjected to the torsion forces of two wheels. Through excellent engineering, half of the torsion forces of the two wheels were mitigated by the suspension system built around the original axle. This design not only enables the drive of two wheels by a single axle but with clever usage of gears and bearings on both the axle and tube around the axle, the suspension system can rotate around its axle for 360 degrees. This ability to rotate in extreme angles would enable the vehicles to traverse very difficult terrains and still provide maximum traction, as the suspension system curved with the terrain so that all the wheels were always in contact with the ground.

The boomerang suspension.
Source: Engesa manual

Engesa

Engenheiros Especializados SA, or Engesa, was the largest and the most famous company in the Brazilian armored vehicle industry. Engesa was founded in São Paulo in 1958 by José Luiz Whitaker Ribeiro. Initially, Engesa focused on oil prospecting, production, and refinement equipment. With the invention of Engesa’s total traction suspension system, they were hired to modernise and build trucks for the Brazilian Army.

In 1969, Engesa introduced its flagship boomerang suspension for its wheeled vehicles. Only a single axle was needed to drive the 4 wheels which were in constant contact with the ground, providing constant traction. At the time, this was a simple, sturdy, and relatively cheap construction. Although not fit for heavy vehicles, it was perfect for the armored vehicles that Engesa would start to manufacture in the near future.

With Engesa’s involvement in refitting the Army’s trucks with the Total Traction system and the development of their Boomerang suspension, they were contacted by the Army to help develop the wheeled vehicles together with the PqRMM/2 team. This joint development resulted in the EE-9 Cascavel and the EE-11 Urutu. The EE-9 Cascavel paved the way for Engesa to take its position as the leading company of the Brazilian Defense Industry.

Engesa Logo.
Source: https://en.wheelsage.org/engesa/logotypes/488339

The Cascavel is Born

With the installation of the boomerang suspension and the redesign of the hull, the basis was laid for what would become the EE-9 Cascavel. The mock-up of the CRR was built in early 1970 and presented to General Plínio Pitaluga, a veteran of the FEB. It seems that, almost immediately after the mock-up was finished, the PqRMM/2 engineers started the production of the first working prototype.

Nearing the end of the construction of the CRR prototype, a new turret was developed for the new 6 x 6 vehicle. The CRR mounted a redesigned VBB-1 turret with a turret bustle. The VBB-1 turret was a copy of the M8 Greyhound turret and was manufactured by Fundições Alliperti S/A and Avanzi. It is noted that the redesigned VBB-1 turret was manufactured by Companhia Siderúrgica Nacional (CSN) (English: National Steel Company). Although the CRR received the redesigned VBB-1 turret, the original plan was to mount copied and redesigned M3 Stuart turrets with an added turret bustle, which were also produced by CSN. But, by the time the CRR prototype was finished, the redesigned M3 Stuart turrets were not ready yet.

The finished prototype of the CRR with the VBB-1 turret and boomerang suspension.
Source: Ford M-8 Greyhound no Exército Brasileiro – Expedito Carlos Stephani Bastos

The prototype of the CRR was completed in 1971. It used a copied and redesigned M8 turret armed with a 37 mm cannon and a .50 machine gun on top of the turret. The turret was a fully enclosed turret designed by Engesa. The vehicle-mounted run-flat tires were previously developed by Novatracão for the VBB-1 project. The vehicle’s exhaust was located on the right side of the rear. The vehicle had a crew of 3. The driver was positioned in the middle of the hull and had a raised structure for his head and the sights. The remaining two crew members were the gunner and the commander/loader.

The CRR was extensively tested by the Brazilian Army, tests which were overseen by the PqRMM/2. During the tests, the CRR prototype travelled over 65,000 kilometers and performed various mobility tests. The tests were successful, as the construction of a 5 vehicle pre-series was approved. The number of pre-series vehicles would increase to a total of 8 vehicles after the Diretoria de Pesquisa e Ensino Técnico do Exército (DPET) (English: Army Directorate of Research and Technical Education), which oversaw the PqRMM/2 developments, signed a contract with Engesa in June 1971 for the development and construction of the pre-series. Production of the 8 pre-series vehicles for the Brazilian Army began in 1972 and was finalized in September 1975.

The Finished CRR with the redesigned M8 turret on the right, and the CTRA (Carro de Transporte sobre Rodas Anfíbio, English: Wheeled Amphibious Troop Transport), a predecessor of the EE-11 Urutu, on the left.
Source: Engesa Brochure

With the signing of this contract, the CRR was officially carried over to Engesa. What is interesting is that the Brazilian Army, despite having developed the CRR, signed off all their intellectual property rights to Engesa. This effectively meant that the Brazilian Army itself would not directly profit from any sales of the future EE-9 Cascavel to other countries. This transfer to Engesa also meant that the CRR would be marketed as the EE-9 Cascavel.

The CRR during trials.
Source: Ford M-8 Greyhound no Exército Brasileiro – Expedito Carlos Stephani Bastos

The Snake Family

The EE-9 Cascavel was part of a family of wheeled vehicles, all named after snakes found in Brazil. These vehicles were the EE-3 Jararaca, EE-9 Cascavel, EE-11 Urutu, and EE-17/18 Sucuri, meaning jararaca, rattlesnake, crossed pit viper, and anaconda, respectively.

A ‘’Cascavel’’ or rattlesnake in English.
Source: https://pt.wikipedia.org/wiki/Cascavel#/media/Ficheiro:Cascavel_-_crotalus_durissus.jpg

The EE-3 was a 4 x 4 reconnaissance vehicle that could mount a wide range of turrets. The EE-9 was Engesa’s reconnaissance vehicle, but due to its mobility and the 90 mm cannon, it would be employed in all kinds of roles. The EE-11 was a troop transport but could be configured to perform all sorts of specialised roles, like Anti-Aircraft, mortar carrier, and ambulance. The EE-17 and EE-18 Sucuri were two 105 mm armed 6 x 6 wheeled tank destroyers.

Logos of Engesa’s Snake family.
Source: Blindados no Brasil – Expedito Carlos Stephani Bastos

The EE-9 was effectively the flagship of this family, even though Engesa thought the EE-11 would be their most successful vehicle. The EE-11 was successful nevertheless, but the Jararaca and the Sucuri were less of a success. The Jararaca was sold in very limited numbers, while the Sucuri was not even sold at all.

Top left: EE-3 Jararaca, top right: EE-9 Cascavel, bottom left: EE-11 Urutu, bottom right: EE-18 Sucuri.
Sources: Engesa brochure, Wikimedia, Forte.jor.br, Military-today.com

Cascavel Designations

With the transfer of the CRR to Engesa also came a new designation. The exact date of when the CRR was designated as EE-9 is unknown. But it is estimated to have been named EE-9 between 1972 and 1973, with EE referring to Engenheiros Especializados (English: Specialized Engineers) and the 9 to its weight in tonnes. The interesting part is that practically every Cascavel exported by Engesa weighed more than 10 tonnes empty. As such, the 9 in EE-9 refers to the 37 mm version of the Cascavel. The weight in a brochure, which is estimated to have been written between 1973 and 1974, refers to the Cascavel with a 37 mm gun as having a 9 tonnes combat weight.

The CRR was redesignated by the Army as well, with the completion of the pre-production batch, to Carro de Reconhecimento Médio (CRM) (English: Medium Reconnaissance Car). This designation is more of a vehicle classification, like the CRR, than a name. This effectively means that the prototype CRR, the pre-production CRM, and the production vehicle EE-9 M1 were all known and sold as EE-9’s.

Since the EE-9 Cascavel was built and developed for 18 years, it received upgrades and design changes over time. To keep track of these changes, a so-called Modelo or Model system was used. It is important to note that different guns or turrets did not mean that the Cascavel was a different model. The Cascavel M2 for example, used all three 90 mm turrets offered by Engesa (HS-90 turret with the French D-921 gun, ET-90 I turret with EC-90 gun, and the ET-90 II turret with EC-90 gun). It was mainly changes to the hull, and especially the transmissions, which caused the Cascavels (Portuguese: Cascavéis) to be classified as a certain model. The Modelos were then further subdivided in production batches or Séries. The differences between the series could be as small as different bolts or different tire nozzles. The development of the Cascavel was a process of evolution, and certain manuals would be written specifically for a range of series of a certain model.

The enthusiast’s guide to Engesa’s Cascavel galaxy

Model

Charatistics

Date

Sold numbers by Engesa

EE-9 M1

The first EE-9 with a manual Clark transmission and a 37 mm gun, practically an improved M8 Greyhound.

1971

Brazil: At least 9 vehicles built, up to a hundred

EE-9 M2

The first EE-9 to have a 90 mm gun as its main armament. Overall hull redesign, widened turret ring, and larger dimensions of the hull to mount the new 90 mm armed turrets. Used a manual Clark Transmission

1975

Brazil: 157
Bolivia: 24
Chile: 83
Libya: 200
*Qatar: supposedly bought 20 Cascavels of unknown model in 1974, no pictures or Brazilian sources confirm this

EE-9 M3

Effectively an M2 Cascavel, but with an automatic MT-540 transmission (the first Cascavel model with an automatic transmission). The first Cascavel model to receive the EC-90 gun.

1975

Libya: 200

EE-9 M4

The M4 was specifically designed, built and sold with the Detroit Diesel 6V53 engine. Overall strengthening of components and further evolution of the hull design. It used an MT-643 transmission.

1979

Brazil (CFN): 6
Colombia: 128
Cyprus: 124
Iraq: 364

EE-9 M5

Used the M4 design but was a cheaper version. It was sold with either an AT-540 or AT-545 transmission in combination with the OM-352A engine.

1981

Bovington Tank Museum: 1
Gabon: 14
Uruguay: 15

EE-9 M6

Automotive enhancements over the previous models. Used the AT-545 in combination with the OM-352A engine.

1982

Brazil: 37

EE-9 M7

The same as the M6, but used an MT643 transmission. This Cascavel was the final model designed by Engesa. It could mount every engine which Engesa sold with the Cascavel, although it only seems to have been used with the OM-352 and the OM352A engines.

1983

Brazil: 215
Ecuador: 32
Paraguay: 28
Suriname: 6
Zimbabwe: 90

Total: around 1,742 sold and less than 1,800 produced.

Arming the EE-9 Cascavel

In 1972, with the start of the construction of the pre-production Cascavels, came the discussion of what the future reconnaissance vehicles of the Brazilian Army should be armed with. Up until then, the reconnaissance doctrine of the Brazilian Army had not changed since their experiences in World War 2, and this old doctrine was still somewhat ingrained in the Army.

An analysis regarding the specifications for a reconnaissance vehicle was released on July 10th 1967. The requirements called for a vehicle which could penetrate its own armor at ranges up to 1,000 meters, fire in all directions (have a turret), a rate of fire of at least 3 shots per minute, and the armament did not have to be used for anti-air purposes. The issue with these requirements is that practically every gun of 20 mm and higher could perform this job.

With the initiation of the VBR-2 project, a discussion emerged within the Army. Recommendations were gathered on what to arm the coming generation of reconnaissance vehicles. The issue was that the Armies (plural) of Brazil, generals, and departments gave conflicting advice about what to arm the vehicle with. Aside from this, the Army also had to take export potential into consideration for Engesa. Since the Brazilian Army completely handed over the project to Engesa, they also wanted to keep logistics and profit for the company as advantageous as possible. By the end of 1972, the Brazilian Army had selected two ranges of potential cannons: 20 to 40 mm or the 90 mm. The Army referred to the FV107 Scimitar for the lower caliber cannons, potentially suggesting that they wanted an autocannon on the Cascavel, and not the 37 mm which they had used so far.

With the selection of the two ranges, a new discussion came at the forefront regarding the purpose of the reconnaissance vehicle. It was recognized that less than 4% of the missions performed by cavalry units during World War 2 were pure reconnaissance missions. The question then was which role would the future Cascavel perform the most and which of these guns was the most suitable. The 90 mm would perform best for anti-tank missions, while the 20 to 40 mm range would be more fit against personnel and overall perform an infantry fighting vehicle role, without being able to carry infantry. It was identified that the EE-9 would not be fit to fill the Infantry Fighting Vehicle role as it did not have the armor to reliably perform this role. At the same time, it was recognized that a 90 mm gun would give the Cascavel a better fighting chance against potential enemy armor. The reasoning was mainly from an isolation point of view, in which a Cascavel on a reconnaissance mission had to fend for itself and take out potential enemies, like tanks. It was determined that the 90 mm was the most suited for this role, considering most of Brazil’s neighbours operated the Shermans as their heaviest armored vehicles at the time, and employed a large number of AMX-13’s and SK-105’s as their other combat tank.

It took up to the second half of the 1970s for the Brazilian Army to completely make up its mind on which cannons should be used on the Cascavel. When this discussion still raged in 1977, the Cascavel with 90 mm gun was already used by Libya against Egypt, and multiple countries ordered the 90 mm cannon.

What might have steered the Brazilians towards eventually deciding to operate a 90 mm Cascavel only force were the trials in Portugal in 1973. Portugal was still in the War of Ultramar as it tried to maintain its colonial empire. Among the vehicles the Portuguese used to fight their opponents was the AML-90. The AML-90 was a 4 x 4 armored car which could be used for reconnaissance and was armed with the potent D-921 90 mm gun.

An AML-90.
Source: https://www.super-hobby.nl/products/Panhard-AML-90-Reconessance-vehicle.html

The Portuguese were approving of the EE-9 Cascavel, which boasted better mobility than their AMLs, but suggested that Engesa should retrial the vehicle when it was armed with the French D-921 gun. As a result, the Brazilian Army ordered the turrets and guns for both the single EE-9 of Engesa and the X1 tank program as well. Engesa retrialled the EE-9 in early 1974, but would not manage to sell the vehicle, as the Portuguese government was overthrown and the War of Ultramar ended. The Engesa team decided to pack up their vehicles and head straight to Libya, where they managed to secure a deal for 200 EE-9 Cascavels armed with 90 mm guns.

From this point on, an increasing number of countries started ordering the 90 mm Cascavel, and it is thought that the popularity of the 90 mm gun, in combination with the performance of the 90 mm gun, caused the Brazilian Army to finally opt for the 90 mm armed Cascavel.

Armoring the EE-9 Cascavel

Until 1968, armor studies were practically non-existent in Brazil. There had been some brief attempts during the revolutions of 1924, 1930, and 1932, but these were mainly of improvised nature. With the initiation of national armored vehicle development also came studies on what to armor the upcoming armored vehicles with. The PqRMM/2 team started off by evaluating all the steel compositions of the vehicles which were acquired by the Brazilian Army over time. The team discovered that the homogenous steel plate of the M2 Half-Track had been heat-treated on the outer side to provide a harder surface, while providing a more ductile surface on the inside to prevent shattering.

The team determined that the effort needed to carry out the necessary techniques for hardening was only justifiable for mass production. With mass-production of the future armored vehicles being expected, the team decided that the development of a dual-hardness plate or bimetal armor would be viable. This type of steel was previously developed in Sweden in 1930 and was known as duplex steel. It would find its first extensive usage on armored vehicles in Brazil. The main difference from other examples of face hardened armor is that two plates of varying carbon content were welded together in production to form a bimetal plate instead of bolting on a hardened plate afterward.

The steel for the bimetal plates was provided by Eletrometal and Usiminas. With Eletrometal providing the high-carbon outer plates and Usiminas the medium-carbon plates. The plates were joined, with 25% of the total plate thickness being high-carbon steel and 75% medium-carbon. The plates were laid on top of each other and subsequently welded around the edges. The bimetal plates were then forged together from 65 mm to about 30 mm thickness and then hot-rolled to the required thickness, This was followed by a quench, tempering, and hardening to the desired hardness. The high-carbon plate was hardened to 700 Brinell while the medium-carbon plate was 250 Brinell.

The average effectiveness of the bimetal plates was about 1.8 times the thickness of an equivalent homogeneous plate against 7.62 mm or 1.5 times the thickness against .50 machine gunfire. This meant that, against .50 machine gun fire, a 16 mm bimetal plate could be used instead of a 25 mm homogenous steel plate. These protection advantages over homogenous plates effectively meant that the Cascavel saved a lot of weight without compromising protection. The outer layer would shatter and blunt the incoming projectile, while the inner layer would relatively move with the bullet, slowing it down and stopping it without shattering.

An interesting tidbit of information according to an ex-Engesa employee who worked at the tempering station was that, at some point, the armor did not perform according to standards. It turned out that the tempering oven was not maintained properly, and the temperature control was faulty. This issue would remain for a few years until it was finally resolved. In order to keep building the armored vehicles, a lot of these plates were approved by quality check anyway, despite being faulty.

Trials in Portugal

In early 1973, Engesa trialled their vehicle in Portugal in an attempt to export it. As previously mentioned, Portugal was fighting against its uprising colonies in the War of Ultramar, also known as the Overseas War in English. At the time, the Portuguese Army was operating a mix of AML-90 and Panhard EBR armored cars in Africa. The Portuguese were impressed by the EE-9 Cascavel, which at that time was most likely still in its CRR configuration, but they suggested that Engesa should arm the Cascavel with the same turret and gun as the AML-90 and return to trial the vehicle again.

With Engesa wanting to arm the Cascavel with a 90 mm gun, the Brazilian Army opted to go for the 90 mm gun on the X1 project as well. They bought 53 turrets and guns from the French company SOFMA. Most of these turrets were ditched, as they did not meet the protection requirements of the Brazilian Army, and local turrets were designed and built as a result. Engesa would arm the EE-9 sent to Portugal with the French turret, but also developed their own turret.

The EE-9, most likely with the final hull EE-9 M1 hull design to solve some practical issues of the CRR configuration, and mounting an HS-90 turret and armed with a D-921 90 mm gun, was trialed again in early 1974. This EE-9 trialed in Portugal could be officially counted as being the first EE-9 M2 Cascavel, considering its 90 mm armament. The problem is that these designs were made before the actual production variant of the EE-9 was known to have been built. For this reason, these projects will be seen as prototypes for both the EE-9 M2, because of its armament, and as prototypes for the EE-9 M1 because of the likely redesigned hull. Portugal would not acquire the EE-9 M2 because a Coup d’Etat put an end to the War of Ultramar.

The influence of Portugal in the success of the EE-9 should not be understated. After the failed attempt to sell the EE-9 Cascavel to the Portuguese, the Engesa team loaded the Cascavel and Urutu back in their freighter and set course to Libya. There, the EE-9 M2 would find success and manage to secure a deal for 200 Cascavels. This deal brought the necessary cash for Engesa to buy a large production plant, and by 1975, the first production Cascavels started rolling from the production line.

The request of the Portuguese to arm the EE-9 with a 90 mm gun effectively helped Engesa to secure a deal with Libya, which would eventually use the Cascavel in combat, generating more sales and making the Cascavel the success it was. At the same time, Brazil also started the development of locally produced turrets for the 90 mm guns for both the Cascavel and X1.

90 mm Turret Designs on the CRR hull

The switch from 37 mm towards the 90 mm would normally mean that the EE-9 Cascavel is an EE-9 M2. These projects were specifically designed on the early CRR hull or on a hybrid between the CRR and the pre-production vehicle which would be designated as Carro de Reconhecimento Médio (CRM) (English: Medium Reconnaissance Car). The problem is that these designs were made before the production vehicle of the EE-9 was built. For this reason, these projects will be seen as prototypes for both the EE-9 M2, because of their armament, and as prototypes for the EE-9 M1, because of the hull. There were two designs: a CRR/CRM hybrid mounting the copied and lengthened M8 turret and armed with a 90 mm gun and a CRR with the French turret.

The CRR with HS-90 turret

The Brazilians made a design with the CRR hull mounting an HS-90 turret. This design was effectively the predecessor of the EE-9 M2 Cascavel. The HS-90 turret was ordered from France and had to be bought as a full package, including the D-921 gun. This Cascavel would have had a gun depression of 8 degrees and an elevation of 15 degrees. Aside from the 90 mm gun, it was also armed with a coaxial 7.62 machine gun. In addition to its armament, it would also be armed with 3 smoke launchers on each rear side of the turret. It could mount a turret top machine gun, night vision sights, radio and intercom, laser rangefinder, and an extra ammunition stowage as optional equipment. It is stated that the EE-9 sent to Portugal used this turret, but it is unlikely that the CRR hull was used for these trials.

The CRR with a HS-90 turret.
Source: Engesa brochure

The reason for this is that the HS-90 turret would not only be too big for the hull and come in collision with both the driver’s vision structure, but also with the engine bay covers. On top of that, the driver’s vision structure would make it virtually impossible to depress or even fire the gun on a flat angle. As such, it seems that the drive for the 90 mm turret caused the hull to be redesigned to resolve these issues.

A sketch detailing the collision issues of the HS-90 turret on the CRR hull.
Done by Godzilla.

The CRR/CRM Hybrid M8 Copy Turret

Another of the designs was effectively a hybrid between the CRR and the later CRM production vehicle. The main hull design change which hints towards it being a hybrid design is the altered headlight guard. On the CRR, the headlight guard was a simple square design, while in this design, it was curved, like on the CRM.

In addition, the copied M8 turret also received some changes which would be seen in the turret later used on the pre-production CRM. Compared to the original CRR turret, this turret had a ventilation inlet on the top of the turret and the antenna, which was originally on the left rear side of the hull, has now been installed on the turret as well. Apart from these 2 features, the turret also provided periscopes for the gunner, apart from the direct sight in the gun mantlet. The 90 mm gun would have a depression of 8 degrees and an elevation of 13 degrees and be installed in a turret with a turret diameter of 1.6 meter. It could mount a turret-top machine gun for anti-aircraft purposes.

In addition, a Perkins type 6357 6 cylinders in-line 142 hp diesel engine, along with a Chrysler type 318 HD V8 196 hp diesel engine, were offered. But Engesa also offered to fit in other engines, depending on the customer’s needs. It would use a 6-speed manual gearbox with five speeds forward and one in reverse. It would have been protected from the front with bimetal armor, protecting against .50 machine gun fire and from the sides from 7.62 mm fire. The exact weight and speed of this design are unknown but are estimated at around 10 to 11 tonnes and 95 km/h, depending on the engine selected.

The CRR with the redesigned M8 turret, armed with a D-921 90 mm gun.
Source: Engesa brochure

The CRM

By September 1975, the production of the pre-series of 8 vehicles, known as the CRM, was finished. The pre-series hulls still carried over much of the design of the CRR hulls. The CRM can be easily identified and distinguished from the CRR in two ways. The first is the redesigned headlight guards, which were now curved instead of simple squares. The second is the relocation of the antenna and most likely the radio set as well. On the CRR, the antenna is located on the left rear of the hull, while on the CRM, the antenna was moved to the turret.

The CRR on the left with the simple square headlight guards and the antenna on the hull, and the CRM on the right with the redesigned headlight guards and without an antenna on the hull.
Source: https://pt.wikipedia.org/wiki/EE-9_Cascavel#/media/Ficheiro:Cascavel1.jpg and Ford M-8 Greyhound no Exército Brasileiro – Expedito Carlos Stephani Bastos

When the CRM was delivered, it seems that the planned altered M3 Stuart copy turrets were still not finished. As a result, the CRM received a much more modernized version of the original CRR turret. The new turret incorporated a ventilation inlet on the left rear of the turret top with the antenna and, most likely, the radio sets moved next to it on the right side. The turret structure on both the commander’s and gunner’s side was also much improved compared to the CRR. A structure was welded on both sides which integrated 2 extra sights to enable a much better overview for the crew.

The CRM, note the added construction on the sides and the redesigned headlight guards.
Source: https://pt.wikipedia.org/wiki/EE-9_Cascavel#/media/Ficheiro:Cascavel1.jpg

The 8 vehicles were almost immediately tested after they were delivered. They had to drive back and forth for 32,000 kilometers between São Paulo to Alegrete. The CRM’s drivo 24/7 and only stop for fuel or if maintenance was needed. The CRM’s seemed to have performed well during these trials, as the CRM, and thus the EE-9 Cascavel, was accepted into service. 102 production vehicles were ordered by the Brazilian Army, all armed with the 37 mm gun.

A Bid for a National Turret

It seems that, around this time, a bid was opened by the Brazilian Army for a locally designed and produced turret to be mounted on the EE-9 Cascavel. Interestingly, of the pictures available, Bernardini built a turret with a 37 mm cannon, while Engesa built a turret with a 90 mm gun. It is very likely that Bernardini also offered the 90 mm turret, as the 37 mm turret was effectively the production turret of the X1, but rearmed with a 37 mm cannon. It is unknown if Engesa built and offered a 37 mm turret. Both of these proposals were built on CRM hulls.

Bernardini’s Entry

As previously stated, Bernardini would have most likely entered the competition with both the 37 mm turret and the 90 mm turret. The turret which Bernardini offered was the production turret of the X1, which was designated BT-90A1. The Brazilian Army had previously bought 53 HS-90 turrets and D-921 90 mm guns. The issue was that the turret armor of the HS-90 was insufficient for the requirements of the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB) (English: Center for the Research and Development of Tanks). As a result, Bernardini and the Brazilian Army started developing a local turret that was armored with 25 mm thick plates to protect the X1 from .50 cal machine gunfire. The design of the BT-90A1 turret was heavily inspired by the HS-90 turret, with the first prototype of the turret (BT-90) even using some components of the HS-90 turret. The main differences between the HS-90 and the BT-90A1 were the addition of a gun shield on the BT-90A1, improved armor, and the BT-90A1 overall being more bulky than the HS-90. The main difference between the 37 mm and the 90 mm turrets from Bernardini was that the 37 mm turret received a new gun shield and was altered for the 37 mm armament.

The CRM mounting Bernardini’s 37 mm turret proposal.
Source: https://armasonline.org/armas-on-line/antigos-equipamentos-do-exercito-brasileiro/

Engesa’s Entry

Engesa’s design was almost a copy of the turret from the X1 prototype, also known as a BT-90 turret. The turrets differed in a very minor way. The rear sides of the Engesa turret, on which the most rearward smoke launcher was installed, went inwards instead of being a flat plate. It is unknown if this turret used bimetal armor or not. The vehicle was armed with a 90 mm gun and a coaxial 7.62 mm machine gun. In addition to its armament, the turret also mounted 2 pairs of 3 smoke grenade launchers on both sides of the rear turret.

EE-9 Cascavel with Engesa’s X1 inspired turret, note the rear turret angling.
Source: http://www.warwheels.net/images/WFVBrazilHAUGH.pdf

Who Won?

It is unclear which company won this specific bid, as both the Engesa turret and the Bernardini turrets were never mass-produced. What most likely happened, was the switch from the D-921 gun to the license-produced EC-90 gun, which was based on the Cockerill 90 mm gun. Somewhere between 1975 and 1976, Engesa got a licensing deal with Cockerill for their 90 mm gun. This was an essential shift, as the forced purchase of both turret and gun from the French became increasingly expensive, and building a local turret would have been much cheaper. This turret design bid was most likely initiated around 1975 and probably ended when Engesa got the license deal in order. It is unclear if a new bid for an EC-90 armed turret was opened, but what is known is that Engesa would design the ET-90 turret which would be used on the Cascavels from that point on.

The EE-9 M1

With the approval of the CRM by the Brazilian Army, 102 production vehicles were ordered. If these 103 vehicles were actually delivered is unclear. Pictures exist where at least 9 production vehicles, known as the EE-9 M1 Cascavel, are shown. According to statements from ex-Engesa employees, the order seems to have eventually been converted into an order for the Cascavel M2 and the EE-9 M1s were supposedly converted to M2s. How many M1’s were eventually built before the Brazilian Army switched the order is unknown. It is estimated that the Brazilian Army changed the order around 1976-1977.

The production model differed from the CRM in a couple of ways. The most notable two were the copied and redesigned M3 Stuart turrets, which were now finally delivered, and the removal of the raised driver structure on the hull. Another very important change was the slanting of the rear hull. This was done to fix the issue of the turret bustle colliding with the engine bay covers, and enabled the usage of low-profile turrets. It is thought that the mounting of the 90 mm HS-90 turret initiated the redesign of the hull to accommodate the turret. Another change was the removal of the exhaust pipe on the right rear side of the hull. The exhaust was now mostly located inside the Cascavel, with the exhaust coming out of the right rear side of the vehicle, above the rear wheel. In essence, the EE-9 M1 was a streamlining of the CRM and mounted the final turret.

The EE-9 M1 was also unofficially called ‘Cascavel Magro’, meaning Skinny Rattlesnake, while the 90 mm armed Cascavels were unofficially known as ‘Cascavel Gordo’, meaning Fat Rattlesnake.

Note the integrated hull driver’s hatch and the redesigned M3 Stuart turret on the EE-9M1.
Source: https://webkits.hoop.la/topic/procurando-imagens-do-ee-9-cascavel-magro

The EE-9 M1 in Detail

The EE-9 M1 weighed about 9 to 9.5 tonnes (9.9 to 10.5 US tons). It was about 5 meters (16.4 feet) long, 2.3 meters (7.5 feet) wide, and the height was around 2.3 meters (7.5 feet). The EE-9 had a three-man crew, consisting of the commander/loader (turret left), gunner (turret right), and the driver in the middle front hull.

EE-9 M1s at a parade, most likely an Independence Day parade around 1975.
Source: https://webkits.hoop.la/topic/procurando-imagens-do-ee-9-cascavel-magro

Hull

The hull of the EE-9 M1 was manufactured from welded bimetal steel plates. The upper front plate was well angled at 60 degrees from vertical. The hull also features two covers which were mounted on the hull at the positions above the boomerang suspension, effectively functioning as mudguards and very minor spaced armor.

The front upper hull plate presented 16 mm (0.63 inch) of bimetal armor at an angle of 60 degrees. The sides and rear were 8.5 mm (0.33 inch) thick at varying angles, and the top and bottom hull were 6.5 mm (0.26 inch) thick. The front of the EE-9 was meant to protect from .50 machine gun fire at an unknown range, while the entire vehicle was protected from 7.62 mm AP rounds at 100 meters (109 yards), and standard 7.62 mm rounds at 50 meters (54 yards).

The EE-9 had two headlights externally mounted on top of both sides of the upper front hull plate. A rearview mirror could be mounted on both headlight guards. A black-out light was installed on the right side of the left headlight. Below the driver’s hatch was a foldable windshield, which the driver could use when driving with an open hatch. It is not completely clear in pictures, but it seems that the driver’s hatch was a two-piece hatch, with the front part being part of the upper front plate, while the back part was part of the top hull plate. The front hatch had three periscopes for the driver for 180 degrees of vision. These periscopes and other periscopes or sights would not have been active or passive night vision equipment unless the Cascavel was ordered with these devices.

The EE-9 M1, note the lengthened M3 Stuart turret..
Source:https://webkits.hoop.la/topic/procurando-imagens-do-ee-9-cascavel-magro

A ventilation inlet was installed on both upper hull side plates, these ventilation inlets are recognizable by their frustum shape. A siren was installed behind the ventilation inlet on the right side of the vehicle. The fuel tank cap of the Cascavel was located on the left side, in the middle of the upper side hull plate. The EE-9 had a large ventilation grille on the rear of the vehicle, reminiscent of the M8, and had a rear light on both sides of the ventilation grill. The engine could be accessed through two large hatches on the hull top rear.

The driver steered the vehicle with a steering wheel and had his gear stick on his right side, and his instrument panel to his left. The acceleration pedal was located on the right side of the steering wheel, and the brake was next to the acceleration pedal on the left. On the left side of the steering wheel was the clutch pedal.

Mobility

The exact engine which would have been used in the EE-9 M1 for the Brazilian Army is unknown. There is a range of potential engines which could have been used, which include the following:

Engine

Fuel

Horsepower

Torque

Perkins 6357 6-cylinder in-line

Diesel

142 at 3,000 rpm

395 Nm at 1,350 rpm (291 ft-lb)

Chrysler 318 HD V8

Gasoline

196 at 4,000 rpm

411 Nm at 2,400 rpm (303 ft-lb)

Mercedes OM352

Diesel

125 at 2,800 rpm

353 Nm at 1,600 rpm (260 ft-lb)

Mercedes OM352A (turbocharged)

Diesel

156 at 2,800 rpm

431 NM at 1,800 rpm (318 ft-lb)

Of these 4 engines, the two most likely would have been the Perkins and the Mercedes OM352 engines. Both were diesel engines. The Perkins was mentioned in an early brochure, and the OM352A is said to have only been used and sold after the first Libyan batch of Cascavels. Considering the Brazilian Army and Engesa switched to the OM352A engine later on, it would not be unlikely that the first engine was a Mercedes. This is all the more likely when one considers Mercedes’ involvement with the motorization of the M8 Greyhound, the half-tracks, and the VBB-1. Sadly, a definitive answer cannot be given at present.

In the end, it probably would not matter too much which engine the EE-9 M1 had, as the Perkins and the OM352 seem to have been somewhat similar in overall performance if one takes the difference of rpm’s into account.

The M1 Cascavel had a top speed of 95 km/h (59 mph) and an operational range of 700 km (353 miles). It had a turning radius of 7.7 meters (8.1 yards) and it could ford a depth of 1 meter (3.3 feet). The Cascavel could climb a 35-degree slope, could climb a vertical obstacle of 0.65 meter (2.1 feet), cross a trench of 1.65 meters (5.4 feet), and had a ground clearance of about 0.5 meters (1.6 feet). The front-wheel could travel for 0.2 meters (0.66 feet), while the rear wheels could travel for 0.9 meters (3 feet). It used 11 X 20 run-flat tires with a diameter of 0.5 meters (1.6 feet). The EE-9 M1 had a distance between the front axle and rear axle of 2.8 meters, and a distance of 1.4 meter (4.6 feet) between the two rear wheels.

The EE-9 used a manual Clark transmission with 5 gears forward and 1 in reverse. In addition, the Cascavel used an Engesa 2 speed transfer case, which allowed the Cascavel to be used in reduced and high gear. By putting the Cascavel in reduced gear, the Cascavel sacrificed horsepower for torque, making it more effective in climbing slopes. The vehicle was 6 x 6 driven, of which the rear 4 wheels were part of the boomerang suspension. The boomerang suspension, in combination with the Engesa 2 speed transfer case, enabled the Cascavel to cross challenging terrain and provide maximum traction in most situations. The power of the engine was distributed to a differential on the front side of the vehicle, and a differential in the rear. The rear differential drove the boomerang suspension with a single axle, which made the boomerang suspension such an ingenious design.

The Boomerang suspension used leaf springs for dampening. The two front wheels were used for steering. The wheels on the boomerang suspension all rotated at the same speed. The front wheels were dampened by large coil springs. The vehicle used hydraulic drum brakes, and was steered with hydraulics as well.

Transmission system of the EE-9 suspension.
Source: Engesa manual

Turret

The turret of the EE-9 M1 was a copy of the M3 Stuart turret. The engineers lengthened the turret to fit radios in the new turret bustle. The turret had two hatches which opened in the same way as on the previous VBB-1 and CRR turrets. In front of those hatches was a machine gun mount. Both the driver and gunner had periscopes around their hatches. An antenna was located on the right rear of the turret. An openable hatch with a vision sight incorporated was installed on both sides of the turret. A basket for stowage was mounted around the entire turret bustle. The commander was located on the left and the gunner on the right.

The armor of the turret is unknown. Considering it was a copy of the M3 turret, the protection levels might have been similar. An estimate of the EE-9 M1 turret protection would be that the front would have been armored with a plate of 51 mm (2 inch) thick at an angle of about 14 degrees from vertical. The gun shield would have been 38 mm thick (1.5 inch). The sides and rear of the M3 Stuart turret were 32 mm (1.26 inch) thick, and the top was 13 mm (0.5 inch) thick. It is worth considering that these are the armor values of the original M3 Stuart turret, and that the EE-9’s armor values might have differed.

The EE-9 M1 turret
Source: https://webkits.hoop.la/topic/procurando-imagens-do-ee-9-cascavel-magro

Armament

The EE-9 M1 used a 37 mm M6 cannon as main armament. The 37 mm M6 had a total length of 2.1 meters (6.9 feet) and a bore length of 1.98 meters (6.5 feet). The 37 mm cannon was able to fire the M51 APC round with 53 mm (2.1 inch) of penetration at 455 meters (500 yards) at a 30-degree angle, and 46 mm (1.8 inch) of penetration at 915 meters (1,000 yards) at a 30-degree angle. It could also fire the M74 AP, M63 HE, and M2 canister rounds. In addition to the 37 mm cannon, the EE-9 mounted a coaxial 7.62 machine gun on the right side of the turret, and a .50 caliber M2 machine gun on top of the turret. Interestingly, some pictures show the .50 machine gun mounted on the front top of the turret, while others show the .50 machine gun mounted on the top rear. The available ammunition of the EE-9 is unknown.

Fate

In the end, only 9 EE-9 M1s have been confirmed to have been built by Engesa. 102 were ordered, but it seems that the rapid developments on the export market of the EE-9 would quickly put an end to the M1 production order. By 1976, the order was probably converted to an EE-9 M2 order. The EE-9 M1s were supposedly converted to M2 standard. How many M1s were actually built and converted remains a mystery. If these EE-9 M1’s ever were delivered to Army units and to which, is unknown. Some sources suggest that up to 50 M1s were built, but they are very vague about this number. It is at least certain that 9 were produced and were later converted to the M2 standard.

Although the M1s did receive serial numbers, it is not known if they were operating in a unit or if they were still serving as parade vehicles. If the EE-9 M1 was used in service, they would have served in the following mechanized platoon structure: 1 radio jeep, 4 reconnaissance jeeps, 2 EE-9 Cascavels, 1 Urutu, and 1 ammunition carrying jeep.

The EE-9 M2 of Brazil.
Source: Private collection

Conclusion

The EE-9 M1 seems to have been more of a stopgap than anything else. Although the Brazilian Army wanted the EE-9 M1, debates within the Army were already heading towards either an autocannon or a 90 mm cannon-armed Cascavel. It was at least quite clear from the start that the rest of the world wanted the 90 mm Cascavel. Considering the EE-9 M2 was already ordered by Libya, the M1 was already outdated before it was even put into production for the Brazilian Army. Eventually, the Brazilian Army folded towards the 90 mm, and made the decision definitive when Engesa could build their own turrets instead of importing them.

As such, the EE-9 M1 itself was an excellent platform with an outdated turret. The Portuguese recognized the capabilities of the EE-9 and were the ones to give the nudge to Engesa to go forward and arm it with a 90 mm. The 37 mm was an armament of the past, while the boomerang suspension and the bimetal armor provided excellent mobility in combination with protection. The Brazilians had succeeded in building their improved version of the M8 Greyhound and established the groundwork for what became Brazil’s most-produced armored fighting vehicle of all time.

Illustrations

The VBR-2, done by Godzilla.
CRR with the VBB-1 turret, done by Godzilla.
The CRR with the M8 copy turret, done by Godzilla.
How the CRR with HS-90 turret would have looked like, note the turret collisions. Done by Godzilla.
The CRR/CRM hybrid with the 90 mm armed M8 inspired turret. Done by Godzilla.
CRM with the modernised M8 inspired turret. Done by Godzilla.
CRM with 37 mm armed BT-90 turret of Bernardini.
The CRM with the 90 mm armed BT-90 inspired turret by Engesa. Done by Godzilla.
The EE-9 M1 Cascavel, done by Godzilla.

Specifications EE-9 M1

Dimensions (L-W-H) 5 meters x 2.3 meters x 2.3 meters (16.4 feet x 7.5 feet x 7.5 feet)
Total weight 9 to 9.5 tonnes (9.9 to 10.5 US tons)
Crew 3 (Driver, commander, gunner)
Propulsion Most likely a Perkins Perkins 6357 6-cylinder in-line or Mercedes OM352
Suspension Boomerang suspension
Speed (road) 95 kmh (59 mph)
Operational range 700 km (435 miles)
Armament 37 mm M6
.30 caliber machine gun (Coaxial)
.50 caliber machine gun (Turret top)
Armor

Hull

Front 16 mm (0.63 inch)
Side 8 mm (0.32 inch)
Rear 8 mm (0.32 inch)
Top 6.5 mm (0.26 inch)
Floor 6.5 mm (0.26 inch)

Turret

Front 51 mm (2 inch)
Gun mantlet 38 mm (1.5 inch)
Sides 32 mm (1.26 inch)
Rear 32 mm (1.26 inch)
Top 13 mm (0.5 inch)

Production At Least 9, up to a hundred

Special thanks to Expedito Carlos Stephani Bastos, the leading expert in Brazilian vehicles, please visit his website for further reading on Brazilian vehicles: https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts and the website https://tecnodefesa.com.br, Adriano Santiago Garcia, a Captain in the Brazilian Army and ex-company commander on the Leopard 1 and ex-lecturer on the Brazilian Armored School, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near endless ability to talk about them.

Sources

Engesa EE-9 Cascavel 40 anos de combates 1977-2017 – Expedito Carlos Stephani Bastos
Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6 – Expedito Carlos Stephani Bastos
Blindados no Brasil – Expedito Carlos Stephani Bastos
Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives – Hélio Higuchi, Paulo Roberto
Bastos Jr., Reginaldo Bacchi
Engesa manuals
Engesa brochures
http://www.lexicarbrasil.com.br/
Dual Harness skin stops armor-piercing projectiles Article of Richard M. Ogorkiewicz
Sipri Arms Transfer Database

Stuart: A history of the American Light Tank, Volume 1 – R.P. Hunnicutt
Armored Car: A history of American Wheeled Combat Vehicles – R.P. Hunnicutt

Personal correspondence with Ex-Engesa Employees
Personal correspondence with Expedito Carlos Stephani Bastos
Personal correspondence with Paulo Roberto Bastos Jr.
Personal correspondence with Adriano Santiago Garcia

Categories
Cold War Brazilian Armor WW2 Brazilian Armor

T17 Deerhound in Brazilian Service

https://www.tanks-encyclopedia.com/images/drapeaux/brazil_r.jpg Brazil (1944-1972)
Armored Reconnaissance vehicle – 54 bought

With World War 2 in full swing and the United States at war with the Axis, the United States sought to secure its position on the American continent. Through multiple ways, the United States would successfully influence all the American countries to either side with the Allies or stay neutral throughout the conflict. Brazil was one of these American countries which joined the side of the Allies in August 1942, partially because German submarines sank multiple Brazilian ships close to the Brazilian coast and due to Getúlio Vargas’ pragmatic rule of Brazil.

One of the realisations of the United States in their attempt to secure the American continent was that most of the equipment of the armies and infrastructure of the American countries were seriously outdated. Brazil was no exception, as it still operated five Renault FTs and 23 L3/35 in a mixed squadron. During World War 2, Brazil would acquire aid in industry, logistics, army modernisation, and equipment through Lend-Lease. The latter was also done to help deter any neutral American nation from siding with the Axis.

Among the equipment Brazil received were 54 T17 Deerhounds, making Brazil the only country to operate the T17 in regular Army units. In fact, the T17 would be Brazil’s first 6 x 6 wheeled armored fighting vehicle and began the story of 6 x 6 wheeled vehicles in Brazil which still continues to this day with the EE-9 Cascavel and the Guarani APC. Sadly, the Deerhound has become a forgotten vehicle in the United States and it would meet an equal fate in Brazil, being overshadowed by the successful and beloved M8 Greyhound.

A Brazilian T17 Deerhound.
Source: https://cyberplasticmodeler.blogspot.com/2014/07/walkaround-vol11-t17-deerhound-6×6.html

The T17 Deerhound

The development of the T17 Deerhound was initiated after Spring 1941, when the British Purchasing Commission submitted their requirements for both medium and heavy armored cars which they wanted to receive as soon as possible. At the same time, the American Armored Force Board came forward with their specifications for a wheeled vehicle based on the British experience in Africa. The medium armored car was designated as T17, and both Ford and Chevorolet came forward with a design.

The Ford design is what is known as the T17 Deerhound today, with a 6 x 6 suspension system. The Chevrolet design was a 4 x 4 driven vehicle that was redesignated as T17E1 and would later be known as the Staghound. Ford’s design initially used two 90 hp Ford engines, but these were replaced with two Hercules JXD 110 HP petrol engines. Both engines used an individual transmission and linked up to a single transfer case. The T17 had, as a result, 8 forward and 2 reverse gears.

The first pilot was delivered in March 1942 but was rejected due to numerous mechanical defects and extensive failures in the axles and transmission. The second prototype would attempt to solve these issues, but would cause the vehicle’s dimensions and weight to become too excessive and it was rejected again. As a result, the contract of the T17 Deerhound was reduced to 250 vehicles. Originally meant for the British, which had named it T17 Deerhound, they rejected it as well. As a result, the 196 T17 Deerhounds were delivered to the Military Police units in the US with their guns removed, while, unknown to many, 54 T17s were delivered to Brazil through Lend-Lease.

The T17 at Aberdeen Proving Ground on December 4th 1942.
Source: Armored Car – R.P. Hunnicutt

The T17 in Brazil

Brazilian sources are unclear as to when Brazil received the T17 Deerhounds, as they estimate the delivery of the T17 from 1943 to 1944. What is known is that 18 T17 Deerhounds were put into service in September 1944. It would receive the local classification of Carro Blindado de Reconhecimento or CBR (English: Armored Reconnaissance vehicle). The Deerhounds would serve as both reconnaissance and command vehicles.

5 T17 Deerhounds of the 3º RMM during an Independence Day Parade on September 7th 1944.
Source: https://caiafamaster.com.br/destaque/um-seculo-de-blindados-no-brasil-braco-forte-na-defesa-da-patria-aco-no04/

The T17 was delivered to 3 units, 2 were Regimento Motomecanizado’s (RMM) (English: Motomechanized Regiments) and the other was a Batalhão de Polícia do Exército (BPE) (English: Police Battalion of the Brazilian Army). The Regimento Motomecanizado’s would later be renamed and reorganized on May 17th 1946 as Regimento de Cavalaria Mecanizado (RCMec) (English: Mechanized Cavalry Regiment).

Markings would also start to be standardized around this time. From pre-1946, when they used a star in the colors of Brazil, it was replaced from 1946 to 1983 with the Cruzeiro de Sul, translated as Southern Cross. In addition, the registration of the vehicles was also standardized, with the EB10-XXX format. EB referred to Exército Brasileiro, the 10 to the type of vehicle, in this case, a reconnaissance vehicle, and the XXX (for example, 084) to which vehicle.

Drawing of the pre-1946 marking on the left, and the Cruzeiro de Sul on the right.
Source: Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6

From November 1953, the units would be redesignated as Regimento de Reconhecimento Mecanizado (RRecMec) (English: Mechanized Reconnaissance Regiment) until about 1968-1969, after which they would be designated as RCMec again, which they maintain to this day. Since sourcing mostly refers to the RRecMec and this was the longest period in which the T17 served under this regiment designation, the RRecMec designation will be used for future chapters.

2º RRecMec

One of the regiments to receive 18 Deerhounds was the 2º RMM, stationed in the Rio Grande do Sul state, at Porto Alegre. There, they would be operated along with M3A1 Stuarts, but also with M3A1 Scout Cars and Willys Jeeps. Practically, nothing is known about the T17s which served in the 2º RRecMec, except for a single one. EB 10-084, nicknamed ‘Tuiuti’, was retired in 1970, and turned into a monument in Jaguarão in Rio Grande do Sul state. If this particular T17 still exists is unknown. This is because none of the known surviving T17s have the same registration numbers or markings. There are three Deerhounds without any markings at all, so there might be a slim chance that one of these is the ‘Tuiuti’.

The Tuiuti on display as a monument.
Source: https://www.defesabrasil.com/forum/viewtopic.php?t=18372

3º RRecMec

The 3º RRecMec is, relatively speaking, a more documented regiment regarding the T17. 18 T17 Deerhounds were delivered to the then 3º Regimento Motomecanizado’s on September 4th 1944, stationed in Bagé in Rio Grande so Sul. There, they equipped the 3rd and 4th Esquadrão de Carros Leve (English: Light Vehicle Squadron) and served alongside 34 M3A1 Stuarts which were delivered around the same time.

T17 Deerhound of the 3º RMM during an Independence Day Parade on September 7th 1946. Note the old markings.
Source: Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6

With the switch to the RCMEC, the Deerhound would serve under a new composition of two reconnaissance squadrons consisting of T17s, M3A1 Scout Cars, and Willys Jeeps, a Light Tank Squadron of M3A1 Stuarts, a command squadron, and a service squadron. The 18 T17s would receive the registrations from EB10-126 to 136, and from 138 to 141. A single Deerhound, thought to be used as a command Deerhound, was designated EB10-123. Interestingly, this Deerhound is thought to have been one of the final T17s in service, as it was retired in 1972.

T17 of the 3º RCMec during exercises in 1947.
Source: Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6

1º BPE

Like with the 2º RRecMec, practically nothing is known about the service of the T17 within the BPE, which was located in Rio de Janeiro. The only thing that is known is that at least 3 T17s were delivered to the Military Police. If the BPE received 18 Deerhounds is unknown. What is known is that they used them in parades and that they were supposedly retired around the 1970s. The BPE might have been the last operator of the T17 Deerhound.

T17 Deerhounds of the BPE during an Independence Day Parade on September 7th 1966.
Source: Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6

The Brazilian response to the T17?

Although the T17 was certainly an upgrade compared to the Renault FT or the Fiat Ansaldo L-3, the Deerhound was not popular among the crews. The two Hercules JXD engines had to be synchronized, which was supposedly quite challenging. Because of this, the Deerhounds were usually not really usable. To make matters worse, driving the vehicle on a single-engine in order to get around the synchronization issue would damage the drive shafts. All in all, it seems that the errors which the first T17 prototype had were not really resolved or were simply unfixable because of the T17’s fundamental conception of two engines.

The transmission system of the T17 Deerhound.
Source: Armored Car – R.P. Hunnicutt

Fate

The exact fate of the T17 Deerhounds is unknown. At least 4 vehicles have survived, while the fate of the rest is uncertain. According to Brazilian sources, some of the 37 mm guns were used to arm the 37 mm VBB-1 project. But this is not necessarily presented as a fact. It would not be surprising if the Brazilian engineers used these guns, considering it would have been cheaper to repurpose the guns, and the T17 was practically retired when these projects started in 1970. It is thought that the other 50 T17s have either been scrapped or used as range targets.

The VBB-1.
Source: https://www.lexicarbrasil.com.br/exercito/

The remaining Deerhounds

As far as known, only four T17 Deerhounds still exist in the world. All of these Deerhounds are in possession of Brazil, being retired vehicles from the previous three regiments. The T17s are in mixed condition, with a single vehicle being the most complete, still having both engines, but missing a turret basket. One of the four vehicles is currently being restored by the Centro de Instrução de Blindados (CIBld) (English: Armored Personnel Training Centre).

The most complete T17 is located at the Museu Militar do Comando Militar Sul in Porto Alegre Rio Grande do Sul. This T17 has the registration EB10-170. Considering the 2º RRecMec was located in Porto Alegre, and the EB10-170 is not one of the 3º RRecMec designations, it is quite likely that this Deerhound came from the 2º RRecMec. What is interesting is that the EB10-170 registration is not on all pictures of this T17, suggesting that it might have been painted on at a later date and that the registration might not have been its original registration, or of any other T17 Deerhound at all.

The T17 located at the Museu Militar do Comando Militar Sul.
Source: Deerhound – Paulo Roberto Bastos and Hélio Higuchi

Another T17 was functioning as gate guardian at the 4º Batalahão de Logistica (English: 4th Logistics battalion) at Santa Maria, Rio Grande do Sul. This gate guardian has since been renovated by the CIBld, and is now presented at the Museu de Blindados do Centro de Instrução de Blindados in Santa Maria, Rio Grande do Sul. It has no registration. The hatches of this vehicle are supposedly welded shut, and as such, this vehicle has probably just received an exterior overhaul and is not in running condition.

The T17 located at the Museu de Blindados do Centro de Instrução de Blindados.
Source: Museu de Blindados do Centro de Instrução de Blindados

The third T17 is located at the 1º Parque Regional Manutenção in Rio de Janeiro. Not much is known except that, between 2005 and now, it seems that either the 37 mm gun has been removed or cut off. Considering that this Deerhound is located in Rio de Janeiro, it is quite likely that this vehicle originated from the BPE.

The T17 located at the 1º Parque Regional Manutenção.
Source: http://the.shadock.free.fr/Surviving_T17_T17E1_T18.pdf

The fourth Deerhound is located at the Parque Histórico Marechal Manuel Luís Osório in Tramandaí, Rio Grande do Sul. This vehicle also does not have any registration, but considering it is located close to Porto Alegre, it is quite likely that this Deerhound came from the 2º RRecMec.

The T17 located at the Parque Histórico Marechal Manoel Luis Osorio.
Source: Parque Histórico Marechal Manoel Luis Osorio

Conclusion

The Brazilians needed to modernize their Army and the US needed to supply the Brazilian Army with new equipment to strengthen their resolve on the Allied side. The T17 Deerhound seems to have been more of an equipment dump by the US, than military-aid. It is possible that the Brazilian Army may have ordered the T17 themselves, but either way, it was not much of an improvement. The T17 was not loved by its crews, and the mistakes which had made the US reject it were not fixed or were unfixable.

This was Brazil’s first 6 x 6 and it had made Brazil practically the only country in the world to have operated the T17 in regular Army units. Sadly, the T17 Deerhound ended up with an almost equally tragic story within the Brazilian Army, as it had with the US Army. A rejected vehicle, plagued with significant issues, and most of all, overshadowed by the successful M8 Greyhound.

Illustrations

The T17 Deerhound with the pre-1946 marking. Done by Vesp.
The T17 Deerhound with the Cruzeiro de Sul marking. Done by Vesp.
The Tuiuti of the 2º RRecMec. Done by Vesp.
The T17 located at the Parque Histórico Marechal Manoel Luis Osorio. Done by Vesp.
The T17 located at the 1º Parque Regional Manutenção without its main gun. Done by Vesp.
The T17 located at the 1º Parque Regional Manutenção with its main gun, and the T17 located at the Museu de Blindados do Centro de Instrução de Blindados. Done by Vesp.
The T17 located at the Museu Militar do Comando Militar Sul. Done by Vesp.

Specifications (T17 Deerhound)

Dimensions (L-W-H) 5.5 meters x 2.6 meters x 2.3 meters (16.4 feet x 7.5 feet x 7.5 feet)
Total weight, combat loaded 14.5 tonnes (16 US tons)
Crew 5 (Driver, Co-driver, Commander, Gunner, Loader)
Propulsion Two Hercules JXD 6-cylinder in-line 110 hp gasoline engine
Speed (road) 95 kmh (60 mph)
Operational range 400 km (250 miles)
Armament 37 mm M6
.30 M1919A4 machine gun (Hull)
.30 M1919A4 machine gun (Coaxial)
.30 M1919A4 machine gun (Turret top)
Armor

Hull

Front upper 19 mm (0.75 inch)
Front middle 19 mm (0.75 inch)
Front lower 19 mm (0.75 inch)
Side 19 mm (0.75 inch)
Rear 12.7 mm (0.5 inch)
Top 16 to 9.5 mm (0.625-0.375 inch)
Floor 6,5 mm (0.25 inch)

Turret

Front 32 mm (1.25 inch)
Gun mantlet 25 mm (1 inch)
Sides 32 mm (1.25 inch)
Rear 32 mm (1.25 inch)
Top 19 mm (0.75 inch)

Acquired 54

Sources

Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6 – Expedito Carlos Stephani Bastos
Fiat-Ansaldo CV-3 35 II no Exército Brasileiro – Expedito Carlos Stephani Bastos
Deerhound – Paulo Roberto Bastos and Hélio Higuchi
Armored Car: A history of American Wheeled Combat Vehicles – R.P. Hunnicutt

https://www.defesabrasil.com/forum/viewtopic.php?t=18372
https://caiafamaster.com.br/destaque/um-seculo-de-blindados-no-brasil-braco-forte-na-defesa-da-patria-aco-no04/
https://ecsbdefesa.com.br/carro-blindado-leve-t-17-deerhound-6×6-um-esquecido-no-exercito-brasileiro/

Categories
Cold War Brazilian Armor

XLF-40

https://www.tanks-encyclopedia.com/images/drapeaux/brazil_r.jpg Brazil – 1976
Tracked Self-Propelled Multiple Rocket Launcher – 1 prototype built

In 1973, Brazil began developing the X1 light tank, which was completed later that year. From there, the vehicle would spawn multiple variants, from bridge-laying vehicles to anti-aircraft vehicles. Another variant of the X1 combined the Brazilian research in rocket development, which had started in 1949, with the Brazilian advancements in the X1 project into a tracked self-propelled multiple rocket launcher vehicle, also known as the XLF-40. With this project, Avibras would gain a more prominent role within the defence industry and it would eventually lead to the renowned ASTROS 2 Artillery Saturation Rocket System.

The XLF-40 exhibited at the Escola Preparatória de Cadetes do Exército (EsPCEx) (English: Army Cadets Preparatory School) in Campinas, São Paulo State, in 1976.
Source: Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas

Brazilian rocket development

In 1949, the Escola Técnica do Exército (ETE) (English: Army Technical School) initiated the Brazilian research of rockets, in line with developments from other major countries of the time. The first project was the 114 mm F-114-R/E rocket, which showed promising results. The F-108-R rocket system was then developed in 1956, which could fire multiple rockets and was mounted on a ¾ ton Willys Overland Jeep designated Fv-108-R.

The Fv-108-R Jeep.
Source: Uma realidade brasileira: Foguetes e mísseis no Exército Brasileiro 1949-2012 – Expedito Carlos Stephani Bastos

In 1961, the company Avibras Aerospacial SA was founded in São José dos Campos (SP) by engineers of the Centro Técnico da Aeronáutica (CTA) (English: Aeronautical Technical Center). Avibras would develop Brazil’s first solid synthetic propellant, which would propel them into the rocket and missile industry.

The first major step for Avibras and the CTA was their participation in the Experimental Inter-American Meteorological Rocket Network project or EXAMETNET. This was a project led by the United States to acquire meteorological data for the entire American continent. The US started working together with countries like Argentina and Brazil by providing them with the Arcas rocket to carry out measurements at heights between 20 to 80 km. With Brazil’s participation in the project, the CTA acquired the technology and design of the Arcas rocket and went on to start developing the Sonda 1. The Sonda 1 was a two-stage rocket for which the general idea and technology were copied from the Arcas, but were redesigned for a larger rocket. Although the Sonda 1 itself would not be a success, its design proved fundamental.

Sonda I
Source: https://pt.wikipedia.org/wiki/Sonda_I#/media/Ficheiro:Sonda_I_dimensoes.jpg

In 1965, the CTA transferred the technology of the Sonda rocket to Avibras. With this transfer, Avibras effectively became the most important manufacturer of rockets and missiles in Brazil, as Avibras was responsible for the manufacture of the Sonda 1. After the Sonda 1 project, the CTA started developing the Sonda 2, which was again manufactured by Avibras in the late 1970s. From this point onward, Avibras would, together with the CTA, Instituto de Pesquisas e Desenvolvimento (IPD) (English: Research and Development Institute), and the new Instituto Militar de Engenharia (IME) (English: Military Institute of Engineering), renamed after a merger between the ETE and IMT in 1959, started developing ground-to-ground and air-to-ground rocket systems. One of these rockets was the X-40, which was developed in 1972.

The X-40 was a 300 mm rocket (rockets are unguided, missiles are guided) with a length of 4.45 meters (14.6 feet), weighing 550 kg (1,213 lb), of which a payload of 150 kg (331 lb), and a range of 65 km (40.4 miles). It used a solid propellant as fuel and was manufactured by Avibras. An interesting fact was that this was the first time the Brazilian engineers had used computers to make the calculations for rocket development.

With the development of the X1 family, the promising results of the X-40 rocket, and seeing this as a way to provide more firepower and mobility to the Brazilian artillery units, the IPD initiated the design of a tracked self-propelled multiple rocket launcher, which received the designation Carro de Combate Lançador de Foguetes X-40 (English: Combat Car X-40 Rocket Launcher).

The X-40 rocket at the CTEx in Rio de Janeiro.
Source: FOGUETES NO EXÉRCITO BRASILEIRO 1949 – 2009

The X1 project

The first X1 vehicle was developed and presented at the Brazilian Independence Day Parade on September 7th of 1971. The X1 was a modernization project of the M3 Stuart, carried out by the Parque Regional de Motomecanização da 2a Região Militar (PqRMM/2) (English: Regional Motomecanization Park of the 2nd Military Region), together with Bernardini and Biselli, two Brazilian private companies. The PqRMM/2 was responsible for the development of the wheeled vehicles, but also for the tracked vehicles of the Brazilian Army at the time, and was under the supervision of the Diretoria de Pesquisa e Ensino Técnico (DPET) (English: Army Research and Technical Educational Board), which coordinated the projects.

The tracked vehicles were researched and developed by a team of engineers within the Army and PqRMM/2, which were part of the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB) (English: Centre for the Research and Development of Tanks). The CPDB was a study group of Army engineers which analyzed the possibilities of producing tanks domestically. The first goal was to develop a new family of light tanks using the M3 Stuart as its basis. One of the vehicles which would form part of what we now know as the X1 family, was the XLF-40.

The first X1 during firing trials in 1974.
Source: Blindados no Brasil

The XLF-40

With the success of the X1 project and the completion of the X-40 rocket, the Brazilian Army decided to initiate the development of a rocket system for the X1. The IPD made the first sketches of the Carro de Combate Lançador de Foguetes X-40 (English: Combat Car X-40 Rocket Launcher), which were presented on July 20th, 1976. Further design and construction were immediately initiated in an attempt to build the new vehicle before September 7th of the same year, so it could make an appearance on the yearly Independence Day parade, together with the X1A1 and the XLP-10.

The sketches from the IPD, presented on July 20th 1976.
Source: Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas – Expedito Carlos Stephani Bastos

The XLF-40 would receive three different designations during its development, with its proposal calling it Carro de Combate Lançador de Foguetes X-40, which would be simplified to Carro Lançador Múltiplo de Foguetes (Multiple Rocket Launcher Vehicle). Finally, it received the designation XLF-40. The X referred to it being a prototype, the L to Lançador (English: Launcher), the F to Foguetes (English: Rockets), and the 40 to the X-40 rockets used. Eventually, the full name would be Viatura Blindada Especial, Lancador de Foguetes, XLF-40 (VBE LF XLF-40) (English: Special Armored Vehicle, Rocket Launcher, XLF-40).

The development of the XLF-40 would be carried out by multiple companies, of which Avibras, Bernardini, and Biselli were the most important. Bernardini and Biselli were responsible for the conversion of the hull and installation of the suspension, while Avibras manufactured the rockets.

One of the requirements was that all the systems were completely operable from within the vehicle. The aiming and the launching of the rockets were controlled through radio systems. The rockets could be fired independently or in a volley. To provide a better surface to fire from, the XLF-40 had four outriggers, two on each side, which were operated by hydraulic pistons on each leveling system. These outriggers made the XLF-40 a more stable platform to fire from, increasing its accuracy. Another interesting development was the installation of the TRANSIT global positioning system to better locate the vehicle. This GPS system would help the crews to better estimate the firing arcs of their rockets and be more accurate. An M3A1 Stuart hull was selected to be converted to the XLF-40.

The XLF-40 would only be armed with its rockets and personal weapons for the crew, as the machine gun for the co-driver from the M3 Stuart was removed to provide the same dual hatch as for the driver. This meant that the co-driver had a larger space to enter or exit the vehicle. This style of hatches was first used on the X1 prototype vehicle, but would only be carried out on the XLF-40 and the XLP-10 vehicles. The construction of the XLF-40 prototype was completed in less than 2 months and was able to be presented during the September 7th, 1976 Independence Day Parade.

From left to right: X1A1, XLF-40, and XLP-10 on the September 7th, 1976 Parade.
Source: Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas – Expedito Carlos Stephani Bastos

XLF-40 hull origin theory

In the X1 article, the writer proposed a theory to what may have happened with the X1 prototype after it was completed. This theory suggests that the hull might have been repurposed. Besides the X1, a bridge-laying vehicle designated XLP-10 and a rocket launching vehicle designated XLF-40 were built. Both these variants would use the two hatch opening for the co-driver instead of a hull machine gun. What is interesting is that the XLP-10’s and all production X1’s used a single front side plate and the XLP-10’s missed a characteristic hook on these plates. The XLF-40, though, used the exact same double front side plates design as the X1 prototype and also offered the hook. Additionally, both the X1 prototype and the XLF-40 were converted from an M3A1 Stuart, identifiable from the rear. Considering the X1 prototype was trialled in 1974 and the XLF-40 was built in 1976, it is very likely that the Brazilians removed the turret at some point to subsequently repurpose the X1 prototype hull for the XLF-40 prototype. This makes perfect sense to not waste an otherwise perfectly fine hull, and to reduce the costs of making a prototype.

A picture with the two plate front side plates encircled in red. This style was exclusive to the X1 prototype as all production vehicles used a single plate.
Source: http://www.gbnnews.com.br/2017/10/bernardini-um-historia-de-expertise-e.html#.YKLIoKHRZ1o & Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

With these arguments, the writer hopes to have sufficiently proved his theory that the X1 prototype hull was repurposed for the XLF-40, but would like to reiterate that this is just a theory and only indirect evidence and photographs point towards this possibility. No direct evidence has been found to verify this theory.

XLF-40 in Detail

The XLF-40 weighed 16.6 tonnes combat-loaded (18.3 US tons) and 15 tonnes (16.5 US tons) without rockets. It was 5.98 meters (19.6 feet) long, 2.74 meters (9 feet) wide, and 2.54 meters (8.3 feet) tall. It had a crew of three, with the driver located on the front left of the hull, the co-driver on the front right of the hull, and the commander probably positioned somewhere under where the turret originally was positioned, although there is no confirmation of this.

The XLF-40 at Conde Linhares Military Museum in Rio de Janeiro.
Source: http://www.gbnnews.com.br/2017/10/bernardini-um-historia-de-expertise-e.html#.YKLIoKHRZ1o

Hull and Armor

The hull of the XLF-40 was a slightly lengthened and modified M3A1 Stuart hull. As such, the overall protection for the XLF-40 hull remained the same as that of the M3. The thickness of the plates which were used to lengthen the hull is unknown. The upper front plate of the XLF-40 had an armor thickness of 38 mm (1.5 inch) at 17 degrees vertical, a middle front plate of 16 mm (0.6 inch) at 69 degrees, and a lower front plate of 44 mm (1.7 inch) at 23 degrees. Its sides were most likely about 25 mm (1 inch) thick. The rear armor and the lengthened parts of the side are unknown. Considering the original Stuart had 25 mm (1 inch) thickness on the sides and rear, it would not be unreasonable to assume that the lengthened structure was about 25 mm (1 inch) thick as well. The top plate would have been 13 mm (0.5 inch) thick and the floor plate would have gradually decreased in thickness from 13 mm at the front to 10 mm (0.5 to 0.4 inch) in the rear (although the thickness for the lengthened structure is unknown).

The rest of the XLF-40 had a very similar layout as the Stuart. It had two headlights, one on each side of the front mudguards, two towing hooks on the front hull, two driver style double hatches and, as a result, no hull machine gun.

The XLF-40 had two hydraulic pistons on the front hull, one on each side. These pistons were fixed on a pivot, which allowed them to turn facing the ground when the pistons were utilized. The feet on which the XLF-40 was stabilized had a rotating bar attached to them and to the hull, which caused the pistons to face the ground as the rod of the piston made a complete stroke.

The front of the XLF-40, note the hydraulic cylinders and the rotating bar attached to the feet.
Source: https://wwiiafterwwii.files.wordpress.com/2019/08/launcher.jpg?w=809

The rear curved plate was altered to make room for the rear hydraulic cylinders. The hydraulic cylinder was mounted to the rear by cutting a hole in the curved M3A1 rear plate and sticking the cylinder through it. All the hydraulics of the XLF-40 were powered by the original M3A1 Stuart hydraulic system.

The rear of the XLF-40, note the curved M3A1 Stuart rear plate and the hydraulic cylinders sticking through it.
Source: https://www.nevingtonwarmuseum.com/uploads/9/1/7/5/9175276/3461844_orig.jpg

Mobility

The XLF-40 was powered by a Scania-Vabis DS-11 A05 CC1 6-cylinder in-line diesel engine. This engine produced 256 hp at 2,200 rpm, giving the vehicle a horsepower per tonne ratio of 15.4. It used the same, but revised and locally produced, 5 forward and 1 reverse gearbox, transmission, and differential as the original Stuarts. The XLF-40 would have a top speed of about 55 km/h (34 mph) on roads, but would most likely be much lower when it was armed with the X-40 rockets. The vehicle had an operational range of 520 kilometers (323 miles).

The XLF-40 used a copied and slightly altered VVS suspension system from the 18-ton M4 artillery tractor. It had 4 road wheels divided over two bogies, with 2 bogies per track, two return rollers on each side, a drive sprocket in the front, and an idler wheel on the rear. The 18-ton M4 suspension gave the vehicle a ground pressure of around 0.59 kg/cm2 (8.4 psi). It had an on-ground track length of about 3.22 meters (10.6 feet) and could cross a trench of 1.2 meters (3.9 feet).

Turret and Armament

The turret was replaced by a single plate on which the rocket frame and the needed hydraulics were mounted. This single round plate used the same 1.6 meters (5.25 feet) turret ring diameter as the rest of the X1 family. On the rear of the plate were two hatches for the crew, located in between the rocket rails.

The rotating plate with the two hatches and the launching platform on top.
Source: Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas – Expedito Carlos Stephani Bastos

A frame was built on top of the plate, on which the hydraulic cylinders were located. The rods of these cylinders were fixed to the launching platform so that the rockets could be fired at the needed angle. The launching platform would rest on the frame during travel. Over the years, there seems to have been some development regarding the location of the hydraulic cylinders for the launching platform. The cylinders seem to have been placed much more forward from the launching platform in the early development stages. In later stages, the cylinders seem to have been placed much closer to the hinge point of the launching platform, potentially enabling the rockets to be fired from much steeper angles.

Resting on top of the frame was the launching platform, from which the rockets would be aimed and fired. The frame seems to have been constructed from heavily perforated steel profiles. The holes in the frame were probably meant to save weight, so that smaller hydraulics could be used. The launching platform was 5.5 meters (18 feet) long and between 1.8 to 2.4 meters (5.9 to 7.9 feet) wide. It had three rails from which a rocket could be fired. Each rail had two clamps attached to them in order to clamp the rocket to the rails during travel.

The XLF-40 with its launching platform at its most extreme angle.
Source: https://wwiiafterwwii.files.wordpress.com/2020/09/launcher2.jpg

Initially, the mounting point of the hydraulic cylinder was located in the middle of the launching rails but later seems to have been repositioned towards the rear of the platform due to the relocation of the hydraulic cylinder. The hydraulic cylinders enabled the launching platform to be angled and give the rockets the trajectory to hit their target. The rockets were fired perpendicular from the hull. This was done to provide the launching platform with the needed space to angle the rockets, which is seen to be done at a near 90-degree angle with the rockets aiming almost straight up the sky.

On the left, an XLF-40 firing, and on the right, the XLF-40 at Bernardini. Note the difference in hydraulic cylinder position.
Source: Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas – Expedito Carlos Stephani Bastos

The XLF-40 was armed with 3 X-40 rockets. These rockets had a range of 65 km and used solid propellant as their fuel. The rockets were about 4.45 meters (14.6 feet) long and had a diameter of 300 mm. The rockets weighed 550 kg (1213 lb) each with a 150 kg (331 lb) payload. The rockets could be fired both simultaneously and independently from each other. The XLF-40 had no further armament.

Fate

After the XLF-40 was presented in the Independence Day Parade in 1976, Brazilians would continue testing and improving the vehicle until the early 1980s. It would be tested at the Marambaia Proving Ground in Rio de Janeiro, where it would fire its rockets towards the sea.

The XLF-40 would mostly end up as a testbed more than anything else. It would have a few issues, some of them with the launching platform, but these were said to never have been fully resolved. These issues were part of the reason why the project would not be progressed upon further. In 1981, with the knowledge acquired from the XLF-40 project, Avibras developed the ASTROS 1 rocket system for Iraq, which would eventually lead to the successful ASTROS 2 rocket system that is operated by the Brazilian Army, among others. The development of the ASTROS rocket systems probably contributed to the eventual cancellation of the XLF-40 as well.

With the cancellation, the XLF-40 was added to the Conde Linhares Military Museum collection in Rio de Janeiro at an unknown date.

The ASTROS 1.
Source: Uma realidade brasileira: Foguetes e mísseis no Exército Brasileiro 1949-2012 – Expedito
The XLF-40 at Conde Linhares Military Museum in Rio de Janeiro.
Source: http://www.gbnnews.com.br/2017/10/bernardini-um-historia-de-expertise-e.html#.YKLIoKHRZ1o

Conclusion

In the end, the XLF-40 can be described as a testbed for rocket systems for which potential military service would have been a bonus. It incorporated some relatively advanced technologies, such as the TRANSIT GPS, which would go on to enable Avibras to develop a much more advanced rocket system. The Brazilian Army did not seem initially convinced by the potential of rocket systems after the XLF-40. It would take Brazil until the 1990s to buy the ASTROS system, 10 years after its first conception. This might also have been because the need and money were not there for the expensive system.

The XLF-40 was fundamental for Avibras as a company, and paved the way for the successful ASTROS rocket systems, which were sold by Avibras to countries such as Saudi Arabia, Iraq, Brazil and Indonesia, among others. The ASTROS would become one of Brazil’s most successful and lucrative weapon systems, still being ordered to this day.

Illustrations

The XLF-40. done by Ardhya ‘Vesp’ Anargha.

Specifications XLF-40

Dimensions (L-W-H) 5.98 (19.68 feet) x 2.74 (9 feet) x 2.54 meters (8.33 feet)
Total weight 16.65 tonnes (18.35 US tons)
Crew 3 (Driver, Co-driver, Commander)
Propulsion Scania-Vabis DS-11 A05 CC1 6-cylinder in-line 256 hp diesel engine
Suspension Bogie suspension
Speed (road) 55 kph (34 mph)
Operational range 520 km (323 miles)
Armament 3 X-40 Rockets
Armor

Hull

Front (Upper Glacis) 38 mm (1.5 inch) at 17 degrees
Front (Middle Glacis) 16 mm (0.6 inch) at 69 degrees
Front (Lower Glacis) 44 mm (1.7 inch) at 23 degrees
Sides (guess) 25 mm (1 inch)
Rear (guess) 25 mm (1 inch)
Top 13 mm (0.5 inch)
Floor 13 to 10 mm (0.5 to 0.4 inch)

Turret

25 mm (1 inch) allround

Production 1 Prototype

Special thanks to Expedito Carlos Stephani Bastos, the leading expert of Brazilian armored vehicles https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near-endless ability to talk about them.

Sources

Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., Reginaldo Bacchi
Blindados no Brasil – Expedito Carlos Stephani Bastos
Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas – Expedito Carlos Stephani Bastos
Uma realidade brasileira: Foguetes e mísseis no Exército Brasileiro 1949-2012 – Expedito Carlos Stephani Bastos
http://www.lexicarbrasil.com.br/
Personal correspondence with Expedito Carlos Stephani Bastos
Personal correspondence with Paulo Roberto Bastos Jr.
TM 9-785 18-Ton High Speed Tractors M4, M4A1, M4C, and M4A1C – US Army April 1952.
Stuart: A history of the American Light Tank, Volume 1 – R.P. Hunnicutt

Categories
Cold War Brazilian Armor

VBB-1

https://www.tanks-encyclopedia.com/images/drapeaux/brazil_r.jpg Brazil (1969)
Reconnaissance Vehicle – 1 Prototype Built

Up until 1967, Brazil was dependent on foreign countries for armored vehicles. Throughout and in the aftermath of World War 2, Brazil would receive large numbers of cheap armored vehicles from the United States, including the M3 Stuart and the M4 Sherman, as it had entered the war on the Allied side in 1942. In fact, Brazil had not undertaken any tank design since 1932, and those had only been conversions of tractors and cars into armored vehicles during the revolutions of 1924, 1930, and 1932.

Between 1932 and 1958, the Brazilian Armed Forces created a solid basis of technical institutes from which it could educate technical and research personnel. In turn, these helped the Brazilian automotive industry in developing its own automotive parts and helped in opening laboratories for the manufacturers. In 1967, Brazil set up a plan for the country to become more self-sustaining. The flow of US material had decreased because of its entanglement in the Vietnam War and, after a study, Brazil recognised external dependence on arms suppliers as a serious problem for its political position in South America.

The plan to solve this would be the start of the Brazilian defense industry. The first steps were small, from its first tracked armored vehicle meant for serial production in 1965, called the VETE T-1 A-1 Cutia, to its very first wheeled reconnaissance vehicle with production in mind, designated VBB-1 in 1967. The VBB-1 kickstarted the development of wheeled armored vehicles in Brazil, with the EE-9 Cascavel being the most successful result.

The VBB-1.
Source: https://www.lexicarbrasil.com.br/exercito/

Development

The Viatura Blindada Brasileira 1 (VBB-1), (English: Armored Car of Brazil 1) was developed by the PqRMM/2 (Parque Regional de Motomecanização da 2a Região Militar, Regional Motomecanization Park of the 2nd Military Region), which was a group of Army automotive engineers gathered to study, develop and produce armored vehicles for Brazil. The PqRMM/2 developed its vehicles under the supervision of the Diretoria de Pesquisa e Ensino Técnico do Exército (DPET), (English: Army Directorate of Research and Technical Education). The PqRMM/2 was the birthplace of many of the concepts that resulted in the EE-9 Cascavel and EE-11 Urutu, among others. The first steps of the PqRMM/2, meant to gain experience, was the remotorization of vehicles like the M8 Greyhound and the M2 half-track, which received a diesel engine.

From the experience gained, the PqRMM/2 team initiated the development of a wheeled armored vehicle for reconnaissance. The reason for the PqRMM/2 to develop a wheeled vehicle was because of a study carried out by the Diretoria Geral de Material Bélico (DGMB), (English: General Directorate of War Material), which called for the intensive adoption of wheeled armored vehicles for the Brazilian Army, after having studied wheeled vehicles from various countries. These types of vehicles needed less investment, and were more feasible to develop instead of importing them. The study called for a vehicle like the M8 Greyhound, but simpler.

The reason why the DGMB wanted a vehicle like the M8 Greyhound is because of the experience Brazil had during World War 2 with the vehicle. Brazil sent an expeditionary force, also known as the Smoking Snakes, to fight in Italy alongside the Allies. The Brazilians would operate the M8 during the Italy campaign, and they loved the vehicle. The positive experience with the M8 caused it to be one of the, if not the most impactful vehicles for Brazilian development of armored vehicles. As a result, most of the important wheeled vehicles and the wheeled vehicle program can trace back their roots to the M8 Greyhound during the Italian campaign. The most well known Brazilian vehicle that was based on the M8 Greyhound, albeit heavily improved, was the EE-9 Cascavel.

Early designs

In 1967, the DGMB made a sketch of a 4 x 4 vehicle, armed with a 37 mm cannon which was mounted in a rotating turret. The vehicle needed to have a crew of 3 to 4 members, and was to be sufficiently robust and powerful as the M8, but simpler. This was requested in order not to overburden the PqRMM/2 team more than what they could achieve. The DGMB requirements were passed on to the higher-ups of the Army, which officially collected it under Officia 372, a requirement study for the PqRMM/2 to work from. Further demands were the use of as many off-the-shelf components as possible, in order to profit from the Brazilain automotive industry and to save costs (this would be a common theme for almost all of Brazil’s wheeled vehicles). In addition, the turrets were to be re-used from the obsolete T17 Deerhounds, of which Brazil owned 54 at the time. Finally, the plan was for the chassis to eventually be modified to suit APC, anti-infantry, and anti-air roles.

Sketch of the VBB-1 made by the DGMB in 1967.
Source: Blindados no Brasil

The concept of the 4 x 4 VBB-1 was inspired from the Belgian FN 4RM 62F Auto Blindée. This was one of the vehicles which was studied by the DGMB. Although the VBB-1’s concept was based on the Belgian vehicle, the guns were different. Brazilian doctrine at the time called for the usage of 37 mm guns on reconnaissance vehicles. It can be questioned to some extent if the DGMB might have been stuck in its ways regarding Brazil’s doctrine on the 37 mm, but on the other hand, the VBB-1 was never meant to be groundbreaking or match to its counterparts of the period. Although the concept was based on the Belgian vehicle, the overall design of the VBB-1 seems to have taken most of its inspiration from the M8 Greyhound.

In July 1968, the team led by Lieutenant-Colonel Pedro Cordeiro de Mello, who was the leader of the PqRMM/2, started designing the VBB-1. It would have a 4 man crew and carry spare tires on the sides of its hull. Somewhere around this time, the spare T17 Deerhound turrets got ditched from its development. The reason why is not confirmed by sources. It could be that the development team decided that, while developing a new vehicle with serial production in mind, designing it to mount a turret of which just 57 are available might not be the best decision. It was better to take advantage of the steel foundries and contract a factory to develop turrets. This would give the Brazilian industry experience with turret manufacture and gain another step towards independence. In July of 1986, the first scale model mockup was built. An interesting detail of this model is the complicated raised hull structure towards the turret. Another important detail are the spare tyres mounted on both sides in the middle of the vehicle.

First model of the VBB-1.
Source: Blindados no Brasil

A second model was made, which already simplified the hull construction a bit, and removed the spare tyres in the middle of the first model, replacing them with a continuous side armor plate instead. This was most likely done as the next step within the development of the VBB-1, as the PqRMM/2 had requested the development of so-called bullet-proof tyres, which would theoretically render the spare tyres obsolete in the grand scheme of operations. But it remains unclear if this model was designed with the bullet-proof tyres in mind, or if this model was designed alongside the first model as a proposal.

The model without the spare tyres.
Source: Blindados no Brasil

Development of indigenous run-flat tyres

On June 3rd 1968, Lieutenant-Colonel Mello requested the development of bullet-proof tyres known in Brazil under the acronym P.P.B. (Pneus à Prova de Balas), or run-flat tyres. These tyres were developed by Novatração and would be used for the VBB-1. The selected size of the VBB-1’s tyres was 9.00-20, which was the same size as those of the M8 Greyhound. The tyres were thus interchangeable and the prototypes were extensively tested on the M8’s. The first tyre was developed 3 months after the initial request, and used an outer protective tyre and a separate inner wall. The outer and inner tyre were pushed against the rim lips with an inner rubber ring, also known as a separator. Due to heating issues when used continuously for over 200 km (124 miles), the tyres were rejected.

The next step was a critical development for Novatração. Instead of using an inner tyre, Novatração decided they could use the outer tyre as the inner tyre and the separator ring as a run-flat tyre. This meant that if the outer tyre was punctured, the vehicle could still keep on driving on the separator ring. Another advantage was that crews could now easily field repair any puncturing without the need of removing the wheel from the axle and the outer tyre from the wheel, in order to be able to fix the punctured inner tyre. The new tyre was extensively tested from March 1969 on, and could travel for at least 500 km (311 miles) after it was punctured. Interestingly, the tyre was also tested for a year without any air in the tyre or repairs to the tyre, the tyres held up for 1,200 km (746 miles). The tyres were accepted and delivered in October 1969 to the PqRMM/2. Although the VBB-1 already received its run-flat tyres around March or April of 1969, as a picture dated April 1969, shows a VBB-1 with run-flat tyres.

The VBB-1 tyre on the left and its design by Novatração on the right, note the single outer tyre and the separator around the rim.
Source: Blindados no Brasil

Turret development

Parallel to the development of the tyres was the development of the turret. The initial idea of reusing T17 Deerhound turrets had been ditched, and the PqRMM/2 team opted for a locally produced turret. Sources do suggest that the 37 mm cannons of the T17 Deerhounds were used for the manufacture of the turrets. The new turret was practically a somewhat improved copy of the M8 Greyhound turret. The turret was cast by Fundições Alliperti S/A from SAE 5160 steel, and was further machined by the company Avanzi.

Various gun mantlets were cast by Alliperti and presented on October 25th 1968, along with other components of the turret. A simple gun mantlet with just the main gun hole and a vision hole was selected. This was a simpler gun mantlet than the M8 Greyhound’s mantlet, which was also proposed. Another important difference was that the turret would receive two hatches, instead of an open-top turret like the M8, and it also received a mount for a .50 calibre machine gun in front of the turret hatches. Alliperti produced 8 turrets in total.

Components of the turret and 2 of the proposed gun mantlets. On the left side, an M8 Greyhound like mantlet, and on the right, the simpler mantlet. The simpler mantlet was selected with an extra hole to the side of the 37 mm hole for direct vision purposes.
Source: Ford M-8 Greyhound no Exército Brasileiro

Hull

After the construction of the initial models, work began on building a steel scale model. This steel scale model would start showing clear features from the M8 Greyhound, with the driver and assistant driver’s hatch style being the most notable. The overall shape of the hull, especially the part towards the turret, seems to have been somewhat simplified. A very important detail is the armor values written on the sides of the steel scale model. These values are exactly the same thickness of 3/8 inch (9.5 mm) as the M8 Greyhound’s side armor plates. This might suggest that the overall armor values of the VBB-1 are the same as the M8 Greyhound armor values.

The steel scale model with the armor values written on the plates.
(This picture has been accredited to both the VBR-2 (a 6 x 6 project of the PqRMM/2) and VBB-1 by the writer Expedito Carlos Stehpani Bastos, but after asking the writer himself, he confirmed it was a scale model of the VBB-1, and not the VBR-2.)
Source: Blindados no Brasil

With the initial models and the steel reference scale model completed, work began on the construction of the hull somewhere between July and October 1968. The hull was constructed by the company Trivellato. It reached an advanced stage on October 25th, 1968, when it was photographed. Interestingly, at this point in time, the hull was constructed in accordance with the run-flat tyre concept. However, it is known that the VBB-1, of which a single vehicle was built, was initially delivered as per the spare tyre concept. The first more or less finished vehicle with run-flat tyres was photographed in April 1969, and the first run-flat tyres were made in March 1969. As the hull was initially constructed with the run-flat design, it seems that the PqRMM/2 team decided that it would use the spare tyre concept and cut the side parts of the hull for the spare tyres to be mounted. Somewhere in the early months of 1969, the spare tyre concept vehicle had been delivered, as it was presented to the Army in 1969, and early shooting tests were carried out in 1969, with both vehicles.

Why the PqRMM/2 team decided to cut the sides of the hull for the spare tyres and not wait until the run-flat tyres were delivered, is unknown. It is likely that they wanted to get the vehicle done, and the first set of tyres developed by Novatração did not meet the requirements. They probably weighed the chances of Novatração developing a tyre within specifications and the PqRMM/2 team being able to finish the first concept of the vehicle. With Novatração not having developed a new tyre yet, they went on to develop the spare tyre concept. In addition, an argument can be made that, even though Novatração would have developed a new tyre in time, nothing assured the PqRMM/2 team that that tyre would be significantly better. As converting it back to the run-flat concept would only entail removing the spare tyre mount and welding some extra plates to the side of the hull, the team probably decided that going through with the spare tyre concept was more effective.

The hull which is dated on October 25th 1968. Note the Greyhound tyres.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

The spare tyre concept

When the first version of the VBB-1 with the spare tyres on the side was finished is unknown. It is estimated that it was finished somewhere in between January 1st and March 1969. The reason is because the spare tyre vehicle was presented to the Army in 1969, and shooting tests were carried out with the VBB-1 in this configuration, but in March 1969, the first run-flat tyres were developed and the run-flat concept was first photographed in April 1969.

VBB-1 presented to the Army in 1969.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

Most of the components used for the VBB-1 seem to have been in advanced stages in October 1968. The turret was almost done, the hull was also nearing completion, and the engine was installed in the vehicle as well. Like the VETE T-1 A-1 Cutia before it, and many vehicles after it, the VBB-1 was built with components from numerous private companies. Mercedes-Benz was one of the most important companies involved in the development of early wheeled armored vehicles. Mercedes-Benz Brasil had provided the M8 Greyhounds with new diesel engines, transmissions and differentials during the first stages of the PqRMM/2. For the VBB-1, Mercedes-Benz would again deliver the diesel engine, transmission and a specially developed differential. The differential was an off-center differential which was specially designed by Mercedes-Benz for the VBB-1 project.

Company Component(s)
Mercedes-benz Engine, transmission, differential and other components
Trivellato Hull
Fundições Alliperti S/A Turret
Avanzi Turret
Novatração Run-flat tyres
Engesa Transfer box
Colméia Radiators
MANN Filters
ZF Friedrichshafen Hydraulic steering
DF Vasconcelos Optics
The VBB-1 spare tyre concept.
Source: Blindados no Brasil

The completed VBB-1 with spare tyres was presented to the army in the first quarter of 1969. Almost immediately after it was delivered, the armament and the vehicle were tested. If the tests included anything more than just firing is unclear. It can be expected that it was at least briefly tested and that it performed well enough for the project to carry on. In March 1969, the run-flat tyres from Novatração were finished and, in April 1969, the first picture of the VBB-1 without spare tyres was made.

Firing tests carried out in the first quarter of 1969.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

Run-flat tyre concept

With the development of the run-flat tyres in March 1969, the now finalized VBB-1 was presented in April 1969 in front of the Mercedes-Benz factory in São Paulo. The pride of Mercedes-Benz, or at least their attempt to capitalize on their participation with these Army projects, was shown in the form of a photo album which they had made. This photo album contained pictures of the M8 Greyhound that Mercedes had modernized, and pictures of the VBB-1. Mercedes-Benz Brasil would continue delivering its engines to the rising Brazilian defense industry, which would find their way into the EE-9 Cascavel, EE-11 Urutu, EE-3 Jararaca, and in trucks used for military purposes.

The completed VBB-1 in front of the Mercedes-Benz factory. On the left, a director of Mercedes-Benz Brasil. On the right, Lieutenant-Colonel Pedro Cordeiro de Mello, the leader of the project.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

The VBB-1

The VBB-1 weighed 7 tonnes (7.7 US tons) and was 5 meters (16.4 feet) long, 2.5 meters (8.2 feet) wide, and 2.3 meters (7.55 feet) tall excluding the turret mounted .50 calibre machine gun. Since the VBB-1 was inspired by the M8 Greyhound, its crew was positioned in a similar manner and it is most likely that the crew had the same tasks as in the M8. The VBB-1 was operated by a four-man crew, consisting of the Commander, Gunner, Driver, and Co-driver. The role of loader was most likely carried out by the Commander, like in the M8. The Co-driver would function as a Radio-operator, but if the VBB-1 ever had a radio set installed is unknown.

The VBB-1.
Source: Blindados no Brasil

The hull

The hull was manufactured of steel plates which were welded together. The VBB-1 had a similar style of hull/hatch construction to the M8 Greyhound for the Driver and Co-driver. In a way, the hull can be seen as two parts. A single large and relatively simple bottom hull, and a more complicated structure on top which contains the hatches for the Driver and Co-driver, and on which the turret is mounted.

Picture depicting the simple bottom hull and the more complicated top construction.
Source: Blindados no Brasil

The armor of the VBB-1 is unknown. If the PqRMM/2 team took over the side armor values of the steel mock-up is unknown. However, considering the values of the mock-up, which are the same as the M8 Greyhound, and Brazil’s relationship with the M8, it can be theorized that the armor values of the VBB-1 would be somewhere around the M8’s. The VBB-1’s frontal plate was well angled, at around 60 degrees from vertical. Its sides were flat, but started to angle heavily inwards on the bottom of the hull. The rear armor was practically flat. The more complicated structure of the upper hull used steel plates in complicated and unusual angles, especially on the front part of the hull attached to the sides of the Driver and Co-driver compartment. An interesting pyramid like shape was welded on the left hull side of the vehicle. This was most likely done to protect the spare tyres from frontal fire, and was retained during the conversion to the run-flat concept. It would be probable that this unusual pyramid shape would be either altered or removed altogether if the VBB-1 was ever produced, as its role for the protection of spare tyres was no longer needed and it would have been an overly complicated structure to construct in mass-production.

An example of the complicated angling of steel plates, with this plate being angled inwards, leaving an unusual cavity.
Source: Blindados no Brasil

The driver was positioned on the front left side of the vehicle, and the Co-driver on the right. The turret was located in the middle of the vehicle, and the engine in the rear. The VBB-1 had 2 front lights on both sides, and a black-out light on the left side, next to the front light. On the right side of the hull, the vehicle had a .30 caliber machine gun in a ball mount which was used by the Co-driver. It had a horn and something that resembled an antenna next to the Co-driver’s hatch on the right side of the hull. Behind the horn, the VBB-1 seems to have had pioneer tools. On the rear hull, the VBB-1 had a set of rear lights, including black-out lights.

Mobility

The VBB-1 was powered by a 6-cylinder OM-321 120 hp diesel engine built by Mercedes-Benz. This gave the vehicle a top speed of 90 km/h, with an operational range of 1,200 km (746 miles). It had a turning radius of 7 meters (7.7 yards), and could drive up a 60% slope. The transmission and differential were also produced by Mercedes-Benz, while the transmission box was built by Engesa. The VBB-1 used hydraulic steering.

The OM-321 engine mounted in the VBB-1 in late 1968.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

The vehicle was a 4×4, which meant that every wheel would support, very roughly, about 1.75 tonnes (1.93 US tons). The VBB-1 used 4 run-flat tyres, which were developed and made by Novatração. They were about 1 meter in diameter and used the 9.00 x 20 tyre size, which was also used for the M8 Greyhound.

Turret

The VBB-1 used an altered copy of the M8 Greyhound turret. In contrast to the M8, the VBB-1 turret was not open topped. It had a small plateau on the front side, upon which the mount for the .50 calibre machine gun was installed. Behind, two hatches were installed which folded open to the front. On the sides and the rear, the turret had vision blocks which could fold open if needed. The armor of the turret is unknown. Since it was a copy of the M8 turret, it can be expected that the thicknesses of the armor were potentially the same.

The VBB-1 Turret.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

An important development that the VBB-1 brought was the development and study of armor. Somewhere between 1969 and 1970, the DPET and the Instituto de Pesquisas Tecnológics (IPT) (English: Institute for Technological Research) would test the VBB-1 turret by firing at it with .50 calibre and 37 mm ammunition. The 37 mm cannon was fired at a distance of 500 meters (547 yards) and the .50 calibre at both 250 and 500 meters (273 and 547 yards). The 37 mm and .50 calibre from 500 meters (547 yards) were fired at the front of the turret, and the .50 calibre from 250 meters (274 yards) at the side of the turret. The turret armor managed to withstand both armaments.

The tested turret. Hits from 1. the 37mm cannon, 2. the .50 calibre from 500 meters, and 3. the .50 calibre from 250 meters.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

Armament

The VBB-1 used a 37 mm M6 cannon as main armament, which potentially came from the T17 Deerhound. The 37 mm M6 had a total length of 2.1 meters (6.9 feet) and a bore length of 1.98 meters (6.5 feet). The 37 mm cannon was able to fire the M51 APC round with 53 mm (2.1 inch) of penetration at 455 meters (500 yards) at a 30 degree angle, and 46 mm (1.8 inch) of penetration at 915 meters (1,000 yards) at a 30 degree angle. It could also fire the M74 AP, M63 HE, and M2 canister rounds. In addition to the 37 mm cannon, the VBB-1 mounted a .30 calibre M1919A4 machine gun on the right side of the hull, operated by the Co-driver, and a .50 calibre M2 machine gun on top of the turret. The available ammunition of the VBB-1 is unknown.

Fate

The VBB-1 was extensively tested during 1969 and 1970. It performed in beach trials, mobility trials, and firing tests. The vehicle performed well, but in the end would not be accepted. The reason is because the Brazilian Army wanted a 6×6 vehicle like the M8 Greyhound, and not a 4×4.

From left to right: Beach testing, tests in 1970, mobility test, and shooting tests.
Source: Blindados no Brasil and http://www.geocities.ws/militaryzone_portugal/vbb.htm

Why the PqRMM/2 developed a 4×4 instead of a 6×6 is a mystery. They most likely developed a 4×4 because it was easier and cheaper to build than a 6×6, and thus an excellent vehicle from which to gain experience. The PqRMM/2 briefly considered cutting the VBB-1 and lengthening the hull to create a 6×6 vehicle, but the idea was almost immediately discarded. It was easier and more effective to develop a new vehicle. One of the 8 VBB-1 turrets that were made was briefly used on the CRR prototype, which was a prototype of the EE-9 Cascavel. The VBB-1 is currently used as a gate guardian in front of the Centro Tecnológico do Exército (CTEx) (English: Army Technology Centre). Note that the VBB-1 presented at the CTEx seems to have a different gun than the VBB-1 originally had. It looks like a mock-up on which tubes are screwed together. Considering the state of the VBB-1, it is not unlikely that the 37 mm was removed.

The VBB-1 as a gate guardian at the CTEx. Note the missing vision block on the side of the turret.
Source: https://www.lexicarbrasil.com.br/exercito/

Conclusion

Overall, the VBB-1 seemed to have been a decent vehicle. It performed well in tests, but was outdated from its conception. The VBB-1 did not present anything new and was not better than its counterparts of its time. This is not surprising considering the goal of this project, the lack of experience of the engineers, and taking into account that this was the very first wheeled armored vehicle Brazil had ever developed with serial production in mind.

The Brazilian Army did not want the VBB-1, but a 6×6 instead. The development of the VBB-1 was critical for the future developments of the PqRMM/2 team and the future Brazilian defense industry. Not only did it give the engineers the experience to develop a 6×6 vehicle with a better hull design but, more importantly, it started the development and research of armor and the development of run-flat tyres. The VBB-1 was, most importantly, a vehicle which helped advance the development of Brazilian armored vehicles, and would be the stepping stone towards the famous EE-9 Cascavel and the EE-11 Urutu.

Illustrations

The VBB-1 spare tyre concept. Illustration done by Cut_22.
The VBB-1 run-flat tyre concept. Illustration done by Cut_22.
The VBB-1 as a gate guardian at the CTEx. Illustration done by Cut_22.

Specifications VBB-1

Dimensions (L-W-H) 5 m x 2.5 m x 2.3 m (16.4 feet x 8.2 feet x 7.55 feet)
Total weight 7 tonnes (7.7 US tons)
Crew 4 (Driver, Co-driver, Gunner, Commander)
Propulsion Mercedes-Benz 6-cylinder OM-321 120 hp diesel engine
Speed (road) 90 km/h (56 mph)
Armament .30 caliber machine gun (Hull)
.50 caliber machine gun (Turret top)
37 mm M6 cannon
Armor Unknown, probably somewhere in the region of the M8 Greyhound
Production 1 prototype

Special thanks to Expedito Carlos Stephani Bastos, the leading expert in Brazilian vehicles, please visit his website for further reading on Brazilian vehicles: https://ecsbdefesa.com.br/, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near endless ability to talk about them.

Sources

Personal correspondence with Expedito Carlos Stephani Bastos
Blindados no Brasil – Expedito Carlos Stephani Bastos
Ford M-8 Greyhound no Exército Brasileiro – Expedito Carlos Stephani Bastos
Armored Car – A History of American Wheeled Combat vehicles – R.P. Hunnicutt
Armor Magazine 1973 Jan-Jun
http://www.geocities.ws/militaryzone_portugal/vbb.htm

Categories
Cold War Brazilian Armor

CCL X1A2 Carcará

https://www.tanks-encyclopedia.com/images/drapeaux/brazil_r.jpg Brazil (1977-1978)
Light Tank – 24 Built

At the beginning of the 1970s, the Brazilian Army started developing armored vehicles. They would start with wheeled vehicles. After having successfully developed the prototype concepts which would become the EE-9 Cascavel and the EE-11 Urutu, the Brazilians looked to tracked vehicles. Like the previous wheeled vehicle projects, the engineers started small. They first set off remotorizing readily available M3 Stuarts, and then started developing the vehicle that is known as the X1 light tank. The X1 was a modernization of the Stuart which was armed with a low-pressure 90 mm gun and would be developed into an entire family of vehicles.

An attempt to improve the X1 by fixing some of its design flaws was unsuccessful. The X1A1 was developed to improve on the X1, but in the process only got worse. It was too long and too narrow, which made steering a very difficult task. An extensive rebuilding program would have been required to bring the X1A1 to a usable state, something which was simply not worth it. Considering that both the X1 and X1A1 used the now 30 years old M3 Stuart as their basis, some of the flaws would never have been able to be fixed because of the age of the vehicles.

As a result, it was decided that the development of a completely new tank was the way forward. Capitalising on the experiences gained from the X1 and X1A1 projects, the designated X-15 project would use components and design principles from the previous conversions. It would, for example, use the suspension of the X1A1, but also the X1A1’s turret for the first prototype. The resulting tank of the X-15 project would be known as the X1A2 and be the first (and so far only) serially produced tank which was fully designed in Brazil and used in active service.

The X1A2.
Source: Image Caiafa

The X15

It is suggested that the development of a new nationally designed light tank began quite early. The exact date is unknown, but it might very well already have started with the development of the X1 in 1973, and might have really started to take steps after the failure of the X1A1. Somewhere during the project’s life, the vehicle received the X1A2 designation, most likely when it was decided that the X15 would use components from the X1 series.

The X1A1 in 1976.
Source: https://wwiiafterwwii.wordpress.com/2020/10/18/strange-stuarts-of-brazil/

Nevertheless, the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB) (English: Centre for the Research and Development of Tanks), and the Instituto de Pesquisas e Desenvolvimento (IPD) (English: Research and Development Institute) were studying a light tank concept with two main goals in mind. The first was to abandon the overhaul and the conversion process of the M3 Stuart, which was a laborious task and reached its limit for the goals of the CPDB. The second goal was to create a vehicle which was able to steer properly.

The resulting project was designated X15, with the 15 referring to its planned weight of 15 tonnes (16.5 US tons). To save costs and time, the engineers decided that it would be best to take advantage of the efforts already made by integrating components from the X1 projects in the X15 design. The suspension and turret of the X1A1 were carried over, alongside other components. It supposedly had the same Scania diesel engine as the X1 and X1A1, but with improved horsepower from 260 hp to 280 hp.

The hull would keep many features from the X1A1, but feature an improved armor design with better ballistic shapes for the front hull. The X1A2’s hull was also wider than its X1 predecessors, from 2.4 meters to 2.6 meters (7.9 to 8.5 feet). This widening of the hull would result in a significant improvement in the overall mobility of the X1A2. The X1A2 also featured an Allison CD-500 transmission instead of an M3 Stuart or 18-ton M4 tractor transmission.

CD-500 transmission.
Source: TM 9-1730B – Maintenance Cross-Drive Transmission model CD-500

The X1A2 prototype

The exact date for when the first X1A2 prototype was finished is unknown, but there is proof that the X1A2 prototype hull was nearing completion in July 1978. Considering that a Deputy Chief of the Brazilian Army suggested the interruption of the X1 Pioneiro production for the X1A2 in July 1978, it can be reasoned that the X1A2 prototype was built between July 1977 and July 1978. As mentioned, this prototype integrated the suspension, turret, gun, and engine of the X1A1, while also using new components and design features to fix the issues of the X1A1. It was tested by the Parque Regional de Motomecanização da 2a Região Militar, (PqRMM/2) (English: Regional Motomecanization Park of the 2nd Military Region), after completion. After testing, the vehicle seems to have been accepted and the design of the production version was initiated.

The X1A2 prototype with the French DEFA D-921 gun. Note IPD and CPDB written on the side.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

The production version differed in some significant ways from the prototype. While the prototype seems to have had a 4-man crew, considering 2 sets of sights were installed on both the driver’s and co-driver’s side, the production version only had a set of sights for the driver. In addition, the hull machine gun was also removed. The now vacant space of the co-driver was supposedly filled with additional 90 mm ammo racks. Besides the removal of the co-driver role, the production version X1A2 was also armed with an EC-90 gun.

The EC-90 was a license-produced low-pressure 90 mm gun by Engesa. This gun was based on the Cockerill Mk.3 gun. The switch from the French DEFA (Direction des Études et Fabrications d’Armament) (English: Directorate of Armament Studies and Production) D-921 gun to the EC-90 had multiple reasons. The main reason was that the French company SOFMA (Société Française de Matériel d’Ármament) (English: French Society of Armament Materiel) would only sell their D-921 guns together with the turret, while the X1 family used a local design. The license production of the EC-90 gun made the X1A2 cheaper to produce. In addition to manufacturing costs, the Brazilian Army only operated their EE-9 Cascavels armed with the EC-90. The adoption of the EC-90 on the X1A2 would simplify logistics as well.

The same X1A2 prototype from a different angle, note the two sets of periscopes.
Source: Blindados no Brasil

Production

The X1A2 was produced in two production batches, with the first consisting of 10 vehicles and the second of 14 vehicles. Of these batches, only the first would enter active service, while the second batch mostly ended up as gate guardians and monuments. The first batch X1A2 was officially designated as Viatura Blindada de Combate – Carro de Combate MB-2 (VBC CC Medio Bernardini-2) (English: Armored Fighting Vehicle – Combat Car Medium Bernardini-2), while the second batch was designated as Viatura Blindada de Combate – Carro de Combate MB-2A (VBC CC Medio Bernardini-2A) (English: Armored Fighting Vehicle – Combat Car Medium Bernardini-2A). The reason for this difference was because the second batch used more locally produced components and featured a swing arm for the .50 machine gun, instead of a fixed mount. Interestingly, this swing arm seems to have been incorporated in the X1A2 prototype, but not on the first production batch.

Considering the X1’s similar designations, it would most likely have also been referred to as the Carro de Combate Leve X1A1 Carcará (CCL X1A1 Carcará), (English: Light Combat Car X1 Carcará), but this is more of an educated guess that cannot be actually confirmed. The Carcará was an indigenous crested hawk and was previously the nickname of the X1A1. The nickname most likely carried over from the X1A1 to the X1A2 because the X1A1 project was unsuccessful, and the X1A2 carried over many aspects from the X1A1.

A Carcará hawk.
Source: https://www.britannica.com/animal/caracara

The first production batch was delivered to the 6th RCB in Alegrete, Rio Grande do Sul State, where they would replace a squadron of M4 Shermans. The 6th RCB was the only unit to ever operate the X1A2.

The swing arm.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Bernardini

For the construction of the X1A2, multiple parties and companies were involved. The most important company which built the X1A2 was Bernardini. Bernardini initially manufactured truck bodies and value transport vehicles, and came in contact with the Brazilian Armed Forces by manufacturing trucks for the Brazilian Marine Corps and the Army. With Bernardini being a manufacturer of safes and armored doors, they were requested by the Brazilian Army to help build the X1. After the X1 was successfully developed, Bernardini started developing the X1A2 together with the PqRMM/2 and the CPDB engineers.

Company/Army Component(s)
Bernardini Most likely: hull, turret, engine installation, equipment installation, track mounting and suspension
CSN Steel
Novatração Tracks
DF Vasconcelos Periscopes
Scania-Vabis Engine
Engesa EC-90 90 mm gun
PqRMM/2 Design support and testing
X1A2 during ramp tests at the PqRMM/2.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

The X1A2

Multiple characteristics are presented incorrectly in the book Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives and the Tecnologia Militar Brasileira Magazine. As a result, all the length values were calculated with ratios and are reasonable estimates. Most of the other values are rough estimates. The X1A2 weighed 19 tonnes (21 US tons) and the hull was about 6.06 meters (19.8 feet) long, 2.6 meters (8.5 feet) wide, and 2.45 meters (8 feet) tall. It had a crew of three, with the driver located on the front left of the hull, the commander/loader on the left side of the turret, and the gunner on the right side of the turret.

An X1A2 of the 6th RCB on a 7 September parade in Alegrete.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Hull

The hull of the X1A2 was a completely new design with an improved ballistic shape on the front hull, compared to the Stuart based X1s. The overall hull design still bore much resemblance to the M3 Stuart in general design aspects. The thickness of most of the armor is unknown but is expected to not differ too much from the original M3 Stuart thicknesses. The frontal armor is said to be 50 mm (2 inch) thick but it is unknown if this is for the entire frontal hull. Most of the upper hull was protected by a 50 mm plate angled at about 60 degrees from vertical. On top of that was a small strip of armor right behind the drives periscopes, which slightly extended upwards. The thickness of this plate is unknown, but might also have been 50 mm angled at about 60 degrees from vertical. The lower hull plate is also estimated to have been 50 mm thick and was angled at about 45 degrees from vertical. Under the lower hull plate was another lower hull plate which was probably the same 50 mm thick but angled at about 60 degrees from vertical.

The side, rear, top, and floor armor are unknown, but probably did not differ much from those of the original Stuart, and are thus estimated to have been 25 mm thick. The rear armor is also estimated at 25 mm thick (1 inch). The top plate is estimated to have been about 13 mm thick (0.5 inch), and the floor plate between 13 mm to 10 mm thick (0.5 to 0.4 inch). What is known about the bottom plate, is that it is a dual plate against mines. These values are nothing more than the most likely estimations.

The X1A2 had a headlight on both fenders and a horn on the left fender. It seems that the large upper hull plate was also the access hatch to the Allison CD-500 transmission. It could be bolted loose and subsequently lifted from its position. The sides of the hull were used to mount pioneer tools and were also composed of integrated storage boxes. The X1A2 presents a large lifting hook on both sides of the side engine plate at the rear. On the left fender was presumably another storage box and the exhaust was located on the right rear fender. On the top rear hull were two hatches to access the engine and, in front of those, what looks like an air inlet grill for the engine.

The front hull, note the hatch for the CD-500 transmission.
Source: http://www.primeportal.net/tanks/gino_marcomini/x1a2_carcara/

Mobility

The X1A2 was powered by a Scania-Vabis DS-11 6-cylinder in-line 280 hp diesel engine. It used a three speed Allison CD-500 transmission, the only vehicle of the X1 family to use a different transmission than either the M3 Stuart or 18-ton M4 Tractor transmissions. The X1A2 had a top speed of potentially 60 km/h (37 mph) on-roads, 30 km/h (18 mph) off-road, 15 km/h reverse (10 mph), and an on-road operational range of 600 kilometers (373 miles) and off-road of 350 km (217 miles).

The X1A2 used a copied and altered Vertical Volute Spring Suspension (VVSS) system of the 18-ton M4 artillery tractor. It had 6 road wheels divided over three bogies, with 3 bogies per track, 3 return rollers on each side, a drive sprocket in the front and an M4 Sherman idler wheel on the rear. The newly designed 18-ton M4 Tractor/M4 Sherman hybrid suspension gave the X1A2 a ground pressure of 0.63 kg/cm2 (9 psi). The vehicle could climb a 0.8 meter (2.6 foot) vertical obstacle, and a hill at an angle of 40 degrees. The X1A2 had an on ground track length of about 3.66 meters (12 foot) and could cross a trench of 2.1 meters (6.9 foot).

The 18-ton M4 Tractor/M4 Sherman hybrid suspension. Note the M4 Sherman idler and the three sets of bogies.
Source: http://www.primeportal.net/tanks/gino_marcomini/x1a2_carcara/

Turret

The X1A2 turrets were practically the exact same turrets as the X1A1 turret. The front turret was armored with 25 mm (1 inch) thick steel plates at various angles to protect it from .50 caliber machine gun fire at 200 meters (218 yards). The rear parts of the turret were armored with 12.5 mm (0.5 inch) thick steel plates. It is suggested that the overall turret layout and the internal turret construction and components were more or less copied from the French H-90 turret. It had the exact same turret ring and its overall shape seems to match the H-90. In addition, in the first BT-90 turret of the X1, a lot of equipment was carried over from the H-90, like the periscopes.

The X1A2 turret had a fixed mount for a .50 cal machine gun on the left side of the turret, in front of the commander’s cupola (the second batch had a swing arm mount). The commander’s cupola’s structure was slightly raised from the turret top to provide the commander with a 360 degree view. The antennas of the radio sets were located behind the gunner’s cupola on both sides of the turret. Spare tracks were mounted on the turret bustle sides, which might hint that the turret bustle sides were 12.5 mm (0.5 inch) thick, as it required additional tracks as armor. This placement of the spare tracks meant that the smoke dischargers were moved to the front of the turret, in a set of 3 dischargers on each side. A small light was also installed on the turret side of the commander’s cupola. On the very rear of the turret was a storage box welded on the turret rear, right behind the spare track protected plates.

The turret could traverse 360 degrees in 12 seconds with a hydraulic drive. The base rangefinding is done through graticule rangefinding, but laser and coincidence rangefinders were offered as well.

Side of the X1A2’s turret.
Source: http://www.primeportal.net/tanks/gino_marcomini/x1a2_carcara/

Armament

The production X1A2s were armed with the license produced EC-90 90 mm low-pressure guns manufactured by Engesa. These guns were derived from the Cockerill Mk.3 guns. The low-pressure gun allowed vehicles like the X1A2, but also the 5 tonnes AML-90, to mount a gun with significant armor penetration capabilities.

The EC-90 gun schematics.
Source: Manual de Opercão 9110-733-604 – Torre ET-90 II e Armamento

The trade-off was that these guns would, for a long time, only be able to fire High Explosive Anti Tank (HEAT) ammunition because Armor Piercing (AP) rounds simply had too little muzzle velocity to compete with HEAT. Armor Piercing Fin Stabilized Discarding Sabot (APFSDS) rounds did later appear, but these did not provide any improvement in penetration compared to HEAT rounds. A 90 mm APFSDS round for the later Cockerill guns would penetrate 100 mm (3.9 inch) of armor at 60 degrees from vertical at a range of 1,000 meters (1,090 yards), compared to 130 mm (5.1 inch) at 60 degrees for HEAT at any range. This meant that the APFSDS round mainly served as a round against targets with HEAT countermeasures.

Engesa did develop an APFSDS round for their EC-90 gun on the EE-9 Cascavel on request from Iraq around 1985, but this round would never finish development and only a few test batches were ever produced. The main issue was that the APFSDS round needed to reach higher velocities than the low-pressure rifled guns were designed for. The fixation which kept the sabot together would get damaged when the round was fired. Another issue was the muzzle brake, as the then-current muzzle brakes of the EC-90 guns prevented the use of APFSDS rounds. A pepper pot style muzzle brake was used to solve this issue, but the downside was that the pepper pot muzzle brake was less effective in mitigating recoil. Why the development of the APFSDS round was eventually cancelled is unknown. An Engesa engineer who worked on the APFSDS round believed that they would have been able to fix the problems considering the round started development 8 years before Engesa’s bankruptcy. The employee also stated that the project just did not take off and interest in the round from Iraq was probably not large enough to complete its development.

An Engesa employee with an APFSDS round of the EC-90 at Engesa’s test range.
Source: Private collection

Contrary to common statements, the X1A2 was thus not able to fire APFSDS rounds in the configuration it used at the time. Not only were they not available at the time when the X1A2 was in service, the development of the APFSDS round was never completed by Engesa. It also did not have a muzzle brake that would support the APFSDS round. Since neither requirements were met, the X1A2 never used APFSDS in its loadout. In addition, by the time the APFSDS round could have been ready, interest had already completely shifted to the M41C and the main battle tank projects like the Osorio and Tamoyo.

The X1A2 had access to HEAT, High Explosive Squash Head (HESH), and High Explosive (HE) rounds. The HEAT round was meant for anti-armor purposes and was the X1’s anti-tank round. The HESH round was mainly meant for bunkers, walls and light vehicles, and not as ‘anti-armor’ ammunition. The HE round was used as a general purpose support round. The X1A2 also had access to a white phosphorus smoke round and a HEAT practice round.

Round

Capability

Effective range

Velocity

HEAT (High Explosive Anti Tank)

130 mm (5.1 inch) at 60 degrees from vertical or 350 mm (13.8 inch) flat at any range.

2,000 meters (2,185 yards)

900 m/s

HESH (High Explosive Squash Head)

Meant for bunkers, walls and light vehicles.

2,000 meters (2,185 yards)

800 m/s

HE (High Explosive)

Lethal radius of 15 meters (16 yards)

2,000 meters (2,185 yards)

700 m/s

HEAT-TP (High Explosive Anti Tank – Training Projectile)

Training projectile

2,000 meters (2,185 yards)

900 m/s

White Phosphorus – Smoke

Smoke round

2,000 meters (2,185 yards)

690 m/s

The X1A2 stowed 24 rounds in the turret and an additional 44 rounds in the hull, for a total of 68 rounds of 90 mm ammunition. In addition to the 90 mm, the X1A2 mounted a turret top .50 caliber machine gun (750 rounds) for the commander, and a coaxial .30 machine gun (2,500 rounds). It has a gun depression of 8 degrees and elevation of 17 degrees. The X1A2 had 16 smoke grenades for its 6 smoke dischargers.

Service

The X1A2 was delivered to the 6th RCB in January 1981, with 10 X1A2s replacing the M4 Shermans of the 2nd Tank Squadron. The X1A2s operated together with the X1s of the 1st tank squadron, to which the X1’s were delivered in 1978.

X1A2’s of the 6th RCB.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

The fact that the X1A2 replaced the M4 Sherman and had a larger turret than the X1 led to a very interesting situation. Being used to the 3-man turret of the M4 Sherman, the fresh X1A2 crews tried to adopt the same practice in the X1A2 turret. The turret was very cramped and the practice was abandoned. According to veterans, the commander would have to exit the turret and re-enter the turret to use the radio in the turret bustle. In a real battle situation this would have been impractical and dangerous.

X1A2 crosses a bridge laid by the XLP-10 bridgelayer.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

The X1A2 would encounter various issues during its service life, with the 18-ton M4 tractor torque converter being the biggest issue. The torque converter used by the tank was not designed for a vehicle of the size and speed of the X1A2. What made matters worse was that it was lubricated by poor quality oil used in Brazil. The high concentration of sulphur and low flash point caused the component to wear out much quicker.

To fix this issue, Bernardini suggested replacing the 18-ton M4 torque converter with a TwinDisc converter from the US. Bernardini would acquire one torque converter from TwinDisc and it would be successfully tested. Bernardini ordered enough torque converters to refit the X1A2 fleet, but due to the M41C program, they were never installed.

The controlled differential also caused issues for the X1A2. The more wear the differential had, the harder the X1A2 became to steer. An additional downside compared to the M41 Walker Bulldog was that the entire turrets of the X1 family had to be lifted from the hulls to perform maintenance to the drive shaft of the tanks. Another issue that caused premature wear and difficulty in operation was the lack of instruction manuals for the X1 family as a whole.

X1A2 of the 6th RCB and three X1’s.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Export Attempt

In the early 1980s, the Brazilian government and Bernardini attempted to export the X1A2 to Paraguay, which at the time only operated 21 M3 Stuarts and 3 Sherman Fireflies (the Stuarts being gifted to them by Brazil (12) and the United States (9), and the Shermans by Argentina, eventually replaced by 3 Sherman Repotenciados). As a sign of good will and in an attempt to make the Paraguayans more favourable towards the X1A2, the Brazilian government offered the revitalization of 15 M3 Stuarts. The M3 Stuarts would be upgraded to the X1P standard by receiving a general maintenance overhaul and the Scania-Vabis engine. These Stuarts are still in active service in the Paraguayan Army. Eventually, the X1A2 was never bought, potentially because the Paraguayans wanted to acquire the EE-9 Cascavel instead, of which 28 were delivered in 1985 together with 12 EE-11 Urutus. The X1A2 had a unit price of around 400,000 US Dollars in 1980 (about 1.3 million US dollars in 2021), against 243,600 US Dollars for the EE-9 in 1988 (about 560,000 US Dollars in 2021).

The X1A2 in Paraguay.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Fate

The issues the X1A2 had, in addition to the upcoming M41C upgrades, would cause the Army to refrain from deploying the second batch of X1A2s. They were stored in São Paulo, where the vehicles continued to deteriorate until they were eventually discharged from service in 1989. A couple of these vehicles were turned into gate guardians and monuments, but others were scrapped.

The X1A2s would be gradually replaced from 1988 onwards by the M41C. The X1s, and probably X1A2s as well, were decommissioned in July 1994.

The M41C.
Source: http://www.lexicarbrasil.com.br

Conclusion

The X1A2 was an interesting step for the Brazilian defence industry. It was the first and so far only serially produced, albeit only in limited capacity, tank fully designed in Brazil to see service in the Brazilian Army. It had its issues, but most of these seem to be fixable or were almost fixed by Bernardini. The only real issue the X1A2 would have is the differential, but since it had an improved length to width ratio compared to the X1A1, the steering was already much better. The X1A2 was a promising vehicle if these issues were fixed, and more importantly, if it was not overshadowed by the M41C program.

If the X1A2 was developed a bit earlier, it would have most likely seen more service, and its early flaws would have been fixed. Considering the start of the X1 family only began in 1973 and the X1A2 was only developed from 1976 onwards, while the M41 upgrade programs started their development in 1978, it seems that the first successful attempt of developing a national tank was inevitably too late. The X1A2 is the logical end to the development of Stuart based light tanks with 90 mm guns, which started in 1973. The Brazilians tried to design their own tank and succeeded. From the experience of the X1 program, Bernardini started the development of the M41 upgrade programs and the development of Brazil’s first Main Battle Tank: the MB-3 Tamoyo.

Illustrations

The X1A2 Prototype. Done by Brian Gaydos.
The X1A2 production vehicle. Done by Brian Gaydos.
The X1A2 production vehicle with camouflage. Done by Brian Gaydos.

Specifications CCL X1

Dimensions (L-W-H) 6.06 meters (19.8 feet) long including the gun x 2.4 meters (8.5 feet) x 2.45 meters (8 feet) tall
Total weight 19 tonnes (21 US tons)
Crew 3 (Driver, Commander-Loader, Gunner)
Propulsion Scania-Vabis DS-11 6-cylinder in-line 280 hp diesel engine
Suspension Bogie suspension
Speed (road) 60 kmh (37 mph)
Operational range 600 kilometers (373 miles)
Armament 90 mm D-921 low-pressure gun
.50 machine gun
.30 coaxial machine gun
Armor

Hull

Front (Upper Glacis) 50 mm (2 inch) at 60 degrees
Front (Lower Glacis) 50 mm (2 inch) at 45 degrees
Sides (guess) 25 mm (1 inch)
Rear (guess) 25 mm (1 inch)
Top (guess) 13 mm (0.5 inch)
Floor (guess) 13 to 10 mm (0.5 to 0.4 inch)

Turret

25 mm (1 inch) frontal part
12.5 mm (0.5 inch) rear part

Production 24
Special thanks to Expedito Carlos Stephani Bastos, the leading expert in Brazilian vehicles, please visit his website for further reading on Brazilian vehicles: https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts and the website https://tecnodefesa.com.br, Adriano Santiago Garcia, a Captain in the Brazilian Army and ex-company commander on the Leopard 1 and ex-lecturer on the Brazilian Armored School, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near endless ability to talk about them.
Sources

Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., Reginaldo Bacchi
Blindados no Brasil – Expedito Carlos Stephani Bastos
Jane’s Light Tanks and Armoured Cars of 1984
Worldwide Tank Fire-Control Systems – CIA
http://www.lexicarbrasil.com.br/
Personal correspondence with Expedito Carlos Stephani Bastos
Personal correspondence with Paulo Roberto Bastos Jr.
Caiafa Master
Engesa brochures and manuals
Cockerill brochures
TM 9-785 18-Ton High Speed Tractors M4, M4A1, M4C, and M4A1C – US Army April 1952.
Stuart: A history of the American Light Tank, Volume 1 – R.P. Hunnicutt
Tecnologia Militar Brasileira magazine

Categories
Cold War Brazilian Armor

CCL X1 Pioneiro

https://www.tanks-encyclopedia.com/images/drapeaux/brazil_r.jpg Brazil (1973)
Light Tank – 52+1 prototype Built

Up until 1967, Brazil was dependent on foreign states for armored vehicles. Throughout and in the aftermath of World War 2, Brazil would receive large numbers of cheap armored vehicles from the United States, including the M3 Stuart and the M4 Sherman, as it had entered the war on the Allied side in 1942. In fact, Brazil had not undertaken any tracked armored vehicle design since 1932, and those had only been conversions of tractors and cars into armored vehicles during the revolutions of 1924, 1930, and 1932.

Between 1932 and 1958, the Brazilian Armed Forces created a solid basis of technical institutes from which it could educate technical and research personnel. In turn, these helped the Brazilian automotive industry in developing their own automotive parts and helped in opening laboratories for the manufacturers. In 1967, Brazil set up a plan for the country to become more self-sustaining as a country and militarily. The flow of US materiel had decreased because of its entanglement in the Vietnam War, and after a study, Brazil recognized external dependence of arms suppliers as a serious problem for its political power in South America.

As a result, Brazil developed the first tracked vehicle meant for serial production, the VETE T-1 A-1 Cutia, and developed a range of wheeled vehicles, such as the VBB-1, EE-9 Cascavel, and the EE-11 Urutu. The Army engineers who had started most of these projects had now finally gained enough experience to start undertaking the development of tanks. Like the previous wheeled vehicle projects, the engineers started small. They first set on remotorizing readily available M3 Stuarts, and then started developing the vehicle that became known as the X1 light tank. The X1 was a modernization of the Stuart which was armed with a low-pressure 90 mm gun and would be developed into an entire family of vehicles.

The X1.
Source: Blindados no Brasil

Designation

A commonly occurring mistake is that the X1 and the X1 family are referred to as the X1A. This designation was never used by the Brazilian Army, nor anyone in Brazil. The two authorities on Brazilian armored vehicles (Expedito Carlos Stephani Bastos and the Tecnologia & Defesa Team (Hélio Higuchi, Paulo Roberto Bastos Jr., and Reginaldo Bacchi)) never refer to the X1 as X1A. In addition, Flávio Bernardini, former co-owner of the bankrupt Bernardini S.A. Indústria e Comércio, also refers to the vehicles and the family as X1, and not X1A. This is important, since Bernardini was one of the two main companies to work on the X1 Pioneiro.

The Brazilian Army itself also never referred to it as the X1A either, designating it as the Carro de Combate Leve X1 Pioneiro (CCL X1 Pioneiro) (English: Light Combat Car X1 Pioneer), or more officially, as Viatura Blindada de Combate – Carro de Combate MB-1 (VBC CC Medio Bernardini-1) (English: Armored Fighting Vehicle – Combat Car Medium Bernardini-1). The closest Army designation to X1A would be the VBC CC MB-1a, but this vehicle was the X1A1. It is also good to note that the Brazilian Army was heavily influenced by the US Army from WW2 onwards, and as a result, it would be somewhat illogical for them to designate vehicles as X1A, as their American equipment did not do this.

The X1 designations originate from Lieutenant-Colonel Pedro Cordeiro de Mello, the leader of the project. He was the one who designated the X1, and most likely designated the following vehicles as X1A1 and X1A2, and subsequently nicknamed them as Carcará, a type of indigenous crested bird.

A Carcará hawk.
Source: https://www.britannica.com/animal/caracara

The first mention of an X1A is found in documents from the US. Specifically, a document on Worldwide Tank Fire-Control Systems published on November 1st 1983, 10 years after the first X1 was built. This report was written by the Directorate of Intelligence, the intelligence branch of the CIA. In this document, they refer to the X1A, X1A1, and the X1A2. They further mention that these vehicles were rebuilt M3A1 Stuarts by Bernardini, and were armed with 90 mm guns.

From there on, the X1A designation was used in Jane’s Light Tanks and Armored Cars of 1984, which more or less solidified the designation outside of Brazil. This name was then taken over by other people, and as a result, this designation became common on the internet. The overall lack of knowledge on the X1 family designations can be seen throughout the entire X1 family, as the X1, X1A1, and X1A2, are frequently mixed up. A factor that might have caused this misconception in the first place is the lack of relatively easy obtainable sources from Brazil in English. Most sources are in Portuguese and/or not easy to find. In addition, only in October 2019 did the first source in English appear on the Brazilian Stuarts, which was written by the Tecnologia & Defesa team (Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives).

Genesis

With the Second World War intensifying in Europe, the United States sought to improve their territorial and continental defense against potential invasion. Among this strategy was the arming of South American countries, which were ill-equipped to effectively defend their coastlines. One of these countries was Brazil, which, at that time, operated 5 Renault FTs and 28 Fiat-Ansaldo CV-33/35s. Brazil also realized the obsolescence of its Army, and subsequently took this opportunity to not only acquire modern equipment, but also gain American help in building Brazil’s industry. During World War 2, Brazil would significantly increase its steel production and start producing military equipment. It would also reorganize its Army, with the help of the US, into a modern fighting force. In return, Brazil would deliver war materiel to the United States, it would join the war on the Allied side and participate in combat. Brazil entered the war in 1942 and would participate in the Battle of the Atlantic and send an expeditionary force, called the Smoking Snakes, to fight in Italy.

With Brazil’s participation in World War 2 and its position on the American continent, they were able to acquire American equipment under Lend-Lease. Brazil got their first 10 M3 Stuarts somewhere between early August and September 7th 1941. Brazil received a total of 547 M3 and M3A1 Stuarts. Besides the M3 Stuart, Brazil also acquired 104 M3 Lees, and 53 M4 Shermans (the only South American country to receive the M4 through Lend-Lease, as the US was not that willing to Lend-Lease Shermans to South American countries).

An M3 Stuart of the 3rd Batalhão de Carros de Combate Leve (BCCL) (English: Light Combat Car Battalion), in the 1940s.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivative

Genesis

By the late 1960s, the Brazilian M3 Stuarts were worn out and needed to undergo extensive maintenance. With the US fighting in Vietnam, the availability of cheap and modern vehicles was drastically reduced for countries like Brazil. Due to the amount of M3 Stuarts available in Brazilian stocks, the ease of maintenance, low operational costs, the strategic benefit of light tanks in the South American terrain in the case of war with Brazil’s neighboring countries, and the aforementioned US involvement in the Vietnam War, Brazil did not only extensively maintained the Stuarts, but later selected them for extensive modernization which would become the X1.

An M3 Stuart of Brazil.
Source: https://i.pinimg.com/originals/d6/a1/b8/d6a1b8f1db6b9e421131fe3915a406d8.jpg

The operations to maintain the Stuarts started in the late 1960s under the name Plano Impere, (English: Empire Plan or Plan Empire). The conception of Plano Impere started in 1968, with the reassignment of Colonel Oscar de Abrue Paiva to the 1st Batalhão de carros de Combate Leve (1st BCCL), (English: 1st Light Combat Car Battalion). Colonel Paiva was not happy with this reassignment, as it felt like a step back in his military career. The selection of Colonel Paiva for this assignment was not a coincidence. Paiva was a skilled motor mechanic and the perfect candidate to bring the first BCCL up to standard. Paiva demanded that with his reassignment, he would receive enough funds to revitalize all the 17 M3 Stuarts of the 1st BCCL. He would only receive the funds to fully revitalize 5 Stuarts.

With the 5 Stuarts revitalized, Brazil had decided that it would gift some M3 Stuarts to Paraguay. Since the 5 Stuarts from the BCCL were only recently fully overhauled, they were selected to be sent to Paraguay. Before they arrived there, they were tested by the Parque Regional de Motomecanização da 3a Região Militar (PqRMM/3) (English: Regional Motomecanization Park of the 3rd Military Region). These vehicles performed very well and the quality of the overhaul was of a very high standard. With the successful overhaul of the 5 M3 Stuarts, Colonel Paiva managed to secure the funds he needed for the revitalization of more of his Stuarts, and would set Plano Impere in motion.

The Parque Regional de Motomecanização da 3a Região Militar (PqRMM/3) (English: Regional Motomecanization Park of the 3rd Military Region) started gathering Stuarts from around the country to recondition the vehicles. The Stuarts would receive overhauls to the engines, tracks, radio, electrics, and receive new manuals. During the early and mid 1970s, the best preserved and revitalized vehicles received an ‘A’ or ‘R’ on the sides of their hulls, with the A standing for Aprovado and the R for Rejeitado, (English: Approved and Rejected). The approved Stuarts would be sent to the Parque Regional de Motomecanização da 2a Região Militar, (PqRMM/2) (English: Regional Motomecanization Park of the 2nd Military Region), from where they would be converted to the X1. The rejected Stuarts were scrapped, as the X1s and M41 Walker Bulldogs would replace the M3 Stuarts from 1971 onwards.

An approved M3 Stuart.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivative

In 1969, an Israeli delegation visited the 1st BCCL with the intent of buying old equipment they could use. Although the delegation was only interested in a single M5 half-track, which would not be sold, and Brazil was only interested in selling the Stuarts, which would not be bought, the Israeli delegation did help in the idea of modernising obsolete equipment.

The Parque Regional de Motomecanização da 2a Região Militar

Parallel to the efforts of Colonel Paiva to overhaul the M3 Stuarts together with Plano Impere, the PqRMM/2 team took it to another level and started looking into potentially upgrading the M3 Stuarts. From 1968 onwards, the PqRMM/2 team was tasked with the localization of old vehicles through nationally produced components, and the development of new or improved armored vehicles. The first step was the re-motorization of vehicles such as the M8 Greyhound and half-tracks with nationally produced diesel engines.

With the success of these projects, the PqRMM/2 team went to phase two. During phase two, they would develop their own nationally produced wheeled vehicles for the Brazilian Army. The results of these developments became the VBB-1, the EE-9 Cascavel, and the early concepts of Urutu. They would also start setting up contacts with private companies, which could help the PqRMM/2 team with the manufacture of the vehicles, and eventually carry the projects over to the companies. Of these companies, three stood out, Engesa, Bernardini, and Biselli. While Engesa would be focussed on the wheeled vehicles because of their boomerang suspension, Biselli and Bernardini would be the companies to take on tank building. Another step of phase two was the start of the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB) (English: Centre for the Research and Development of Tanks). The CPDB was a study group of Army engineers which analysed the possibilities of locally produced tanks. The first goal was to develop a new family of light tanks, using the M3 Stuart as its basis.

The CPDB and the PqRMM/2 would start the development of the new family of vehicles in the early 1970s, like they did in phase one. They would remotorize the Stuarts with a nationally produced engine, replacing the Continental W-760-A radial or Guiberson T-1020-A Diesel engines. Three engines were selected to be tested in the M3 Stuart: the Deutz F8L 413 V8 229 hp diesel engine, the MWM TD 228 V8 266 hp diesel engine, and the Scania-Vabis DS-11 A05 CC1 6-cylinder in-line 256 hp diesel engine. Each of these engines was mounted in an M3 Stuart.

The Deutz engine was rejected because it had low torque and required ventilation slits on the side of the hull, which would allow water and mud to enter the engine compartment. The MWM and Scania engines were both very large and required a redesign of the hull. Both Stuarts were lengthened with SAE 5150 steel provided by the Companhia Siderúrgica Nacional (CSN). Of the remaining two engines, the MWM engine was the best, but due to commercial reasons, the Scania-Vabis engine was selected.

The three remotorised M3 Stuarts.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivative

The lengthening of the hull provided a couple of challenges to the PqRMM/2 team. The first challenge was bonding the newly welded SAE 4140 steel bay for the engine to the existing hull. The Brazilian engineers did not have experience in mating such large pieces of steel together, and did not want to consult foreign countries on this issue. If they had welded the steel plates in a more or less conventional manner, the large plates would start to warp due to the heat. The solution was a three-step welding plan: the first step was heating the welded steel plates with a blowtorch, then they would simultaneously start welding the structure on both sides of the steel plate, and they would finally protect the weld with a thermal cover.

The second challenge was that the rear idler shifted 30 centimeter (1 foot) to the rear because of the extended rear. The solution was using the 18-ton M4 artillery tractor suspension. An advantage of this was that the 18-ton M4 suspension was an overall better suspension than the Stuart suspension, and it shared components with the M4 Sherman, which made it a good logistical option. The 18-ton M4 suspension was copied by Bernardini, a company which played an important role in the development and production of the X1, together with the IPD technicians. The suspension would receive some alterations to match local requirements and the tracks were produced by Novatracão. Novatracão was previously responsible for the development and production of the first run-flat tyres in the country.

An 18-ton M4 artillery tractor towing a 155 mm Long Tom.
Source: https://nl.wikipedia.org/wiki/M4_Artillerietrekker#/media/Bestand:M4-HST-tows-155mm-Long-Tom.jpg

The X1 project begins

With the successful remotorization of the M3 Stuarts, and the subsequent suspension change, the CPDB started to look at further improvements in 1973. From there on, more companies would get involved in the construction of the X1. The improvements that were looked into, on top of the remotorization, were improved armament, new electrical systems, and new instrument panels. The 37 mm cannons on the M3 Stuarts were not only obsolete, but also at the end of their lifetime. Crews increasingly had more trouble with the cannons. The decision on the most suitable armament for the X1 was quickly made.

Initial sketch of the X1.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

In the same year, Engesa had trialled the EE-9 M1, which was armed with a 37 mm, in Portugal. Portugal liked the vehicle, but considering they already had the AML-90 in service, they suggested Engesa should mount the AML-90 turret, known as the H-90 and armed with the 90 mm D-921 gun, and then return to trial it again. With Engesa already using the low-pressure 90 mm gun which would be used for the Cascavels for the Brazilian Army as well, the CPDB engineers decided that the low-pressure gun, with its excellent HEAT performance, was the way forward from both a firepower and a logistics point of view.

There was an issue though. The H-90 turret, which had 16 mm (0.6 inch) of frontal and 8 mm (0.3 inch) of side and rear armor, did not meet the requirements of the CPDB. The French company called SOFMA, which sold these turrets and guns, refused to sell them separately. As a result, the negotiations were short and the Army bought both the turrets and the gun, and subsequently ditched the H-90 turret. A total of 53 H-90 turrets and guns were bought, of which one was used for the Cascavel. Work on the new light tank began on June 28th 1973, after authorization from the Diretoria de Pesquisa e Ensino Técnico (DPET), (English: Army Research and Technical Educational Board).

The CPDB and Bernardini S.A. Indústria e Comércio started designing a new turret which could mount the 90 mm gun and meet the armor requirements of the CPDB. Initially, Biselli would develop and build the turret with the CPDB, but due to internal issues and a lack of materials, Bernardini took over the turret project. The new turret was constructed from 25 mm (1 inch) SAE 4140 plates from the CSN. With the 25 mm plates, the X1 turret would be able to withstand .50 machine gun fire at a range of 200 meters (218 yards). Even though the H-90 turret was ditched, the components it used and its concepts were copied into the newly developed turret, designated BT-90.

The Bernardini Factory and the BT-90 turrets.
Source: Blindados no Brasil

The original turret ring diameter of 1.4 meters (4.6 feet) of the Stuart was too small. The turret ring was increased to 1.6 meters (5.25 feet) to mount the new BT-90 turret. The BT-90 turret would later receive some improvements, like the installation of periscopes designed by DF Vasconcelos S/A (who previously had developed the periscopes for the VBB-1), and would be redesignated as the BT-90A1 and become the production version of the X1 turret. The BT-90A1 turret differed in a few ways from the BT-90 apart from the periscopes. Some changes include the installation of a machine gun mount and the integration of the vision slits in the turret instead of periscopes on top of the turret. The BT-90 and BT-90A1 turrets would both use the hydraulic turret drive of the M3 Stuart. An interesting detail is that a BT-90 inspired turret with 90 mm gun was built by Engesa and mounted on a Cascavel, while another Cascavel mounted a BT90A1 turret, made by Bernardini, armed with 37 mm. These turrets were supposedly part of a bid between Engesa and Bernardini on which of the companies would manufacture the turret for the EE-9 in the future.

EE-9 Cascavel with BT-90 inspired turret.
Source: Engesa Operational Manual

Bernardini and Biselli

For the construction of the X1, multiple parties and companies were involved. The two most important companies which built the X1 were Bernardini and Biselli. Both companies manufactured truck bodies and value transport vehicles at the time, and came in contact with the Brazilian Armed Forces by manufacturing trucks for the Brazilian Marine Corps and the Army. Since both companies had some experience in the manufacture of armored vehicles, and with Bernardini being a manufacturer of safes and armored doors, they were requested by the Brazilian Army to help build the X1. Although Biselli would never fully commit to the project, which would result in later issues with the vehicle and eventual departure from a later project, Bernardini would commit and eventually become the tank counterpart to Engesa’s wheeled vehicles.

Company/Army Component(s)
United States The M3 and M3A1 Stuart
Biselli Hull extension, engine installation, equipment installation, and track mounting
Bernardini Turret and suspension
CSN Steel armor
Novatração Tracks
DF Vasconcelos Periscopes
Scania-Vabis Engine
PqRMM/2 Stripping of the Stuart, revision of differential and transmission, radio installation, and testing
PqRMM/3 Overhaul and selection of M3 Stuarts

Construction process of the X1

The construction of the X1 prototype and all subsequent vehicles was more or less done in the following order.

The PqRMM/2 would receive the overhauled Stuart from the PqRMM/3. They would unmount the turrets, and recover the transmission and differentials for revision. The hull and revised transmission and differentials were sent to Biselli. Biselli would extend the hulls, mount the Scania engine, install the revised transmission and differential, install the copied 18-ton M4 suspension produced by Bernardini, provide the vehicle with tracks from Novatracão, and finally install electronics and instrument panels. The hull would then be sent to Bernardini, where the BT-90 turret (or BT-90A1 for the production turret) produced by Bernardini was installed on the hull. The completed vehicle was returned to PqRMM/2, which installed the radio and secondary armament, and finally test drove it for 200 to 300 kilometers (124 to 186 miles) and fired 6 rounds with the low-pressure 90 mm cannon.

The X1 hulls at the Biselli factory.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivative

As previously stated, work on the X1 prototype began on June 28th 1973, and was completed in about 2 months. If this included the extending of the hull and the mounting of the new engine is unknown. It is possible that the PqRMM/2 team used the Stuart which was used to test the Scania engine to save time. The prototype, named X1 by Colonel Cordeiro de Mello, the leader of the PqRMM/2 team, was finished in time to be presented during the Brazilian Independence Day Parade of September 7th 1973.

The first X1 ever built during the Independence Day Parade.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivative

The prototype was extensively tested, and accepted into service under the official designation of Viatura Blindada de Combate – Carro de Combate MB-1 (VBC CC Medio Bernardini-1). What is interesting about these is the MB-1 designation, which means Medium Bernardini-1. This suggests that Bernardini saw this as a medium tank, while the Army saw it as a light tank, which can also be seen on the side of the prototype, stating CL-X1: Carro Leve-X1 or Light Car/Tank X1.

The X1 prototype theory

It is unknown what happened with the X1 prototype afterwards. But after extensive research by studying the context and photographic evidence, the writer of this article proposes a new and very plausible theory to what happened with the X1 prototype and how it connects with the XLF-40.

It seems that the hull was repurposed for the XLF-40 project. Besides the X1, a bridge laying vehicle designated XLP-10 and a rocket launching vehicle designated XLF-40 were built. Both these variants would use the two hatch opening for the co-driver instead of a hull machine gun. What is interesting is that the XLP-10’s and all production X1’s used a single front side plate and the XLP-10’s missed a characteristic hook on the sides. The XLF-40, though, used the exact same double front side plates design as the X1 prototype and also offered the hook. Additionally, both the X1 prototype and the XLF-40 were converted from an M3A1 Stuart, identifiable from the rear. Considering the X1 prototype was trialled in 1974 and the XLF-40 was built in 1976, it is very likely that the Brazilians removed the production X1 turret to arm a production X1 and to subsequently repurpose the X1 prototype hull for the XLF-40 prototype. Just like the prototype turret, this makes perfect sense to not waste an otherwise perfectly fine hull and to cut costs in what was effectively a technology test bed.

A picture with the two plate front side plates encircled in red. This style was exclusive to the X1 prototype as all production vehicles used a single plate.
Source: http://www.gbnnews.com.br/2017/10/bernardini-um-historia-de-expertise-e.html#.YKLIoKHRZ1o & Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

With these arguments, the writer hopes to have sufficiently proved his theory that the X1 prototype hull was repurposed for the XLF-40. The writer would like to reinforce that this is still a theory and so far, only indirect and photographic images seem to point towards the possibility of this theory. No direct evidence was found to either confirm or deny this theory.

Production

With the acceptance of the prototype vehicle, a pre-series of 17 X1s was ordered in December 1973, which would be delivered to the 4th RCB in São Luiz Gonzaga, Rio Grande do Sul State. A series of setbacks would heavily delay the pre-series production, and it took 27 months, until February 1977, for all the pre-series vehicles to be built. The reasons for these delays were embargoes on certain components and issues with Bernardini. The company suffered from management problems, a lack of engineering knowledge, and felt it did not get enough credit. Also, by this time, the X1A1 and X1A2 projects, which were meant to replace the X1, were already in development.

Around this time, the X1’s would receive theri Army designations, the Carro de Combate Leve X1 Pioneiro (CCL X1 Pioneiro). The simple X1 and X1 Pioneiro designations would have been used more commonly. According to sources, it was manufactured under the designation CCL Biselli MB-1 Pioneiro, referring to both Biselli and Bernardini in its designation.

After the production of the pre-series, another batch of 17 vehicles was ordered for the 4th Regimentos de Cavalaria Blindados (RCB) (Englich: Armored Cavalry Regiment), and delivered on August 31st 1978, bringing the total number of X1s to 34 in the 4th RCB. During the same year, 17 other vehicles were delivered to the 6th RCB in Alegrete, Rio Grande do Sul State. Another X1 was delivered to the Academia Militar das Agulhas Negras (AMAN) (English: Black Needles Military Academy), a Brazilian West Point, and later transferred to the Escola de Material Bélico (EsMB) (English: School of Military Materiel). The total production run was 52 vehicles out of a possible 113 vehicles that were considered for production. By the time the X1 Pioneiros were delivered, the X1A2 entered production, which was in turn cancelled in favor of the M41C not long after, being developed from 1978 onwards. An interesting side note is that the X1s were built from both the M3 and M3A1 Stuarts. As a result, some X1s have flat rear plates (M3 Stuart), while others have curved rears (M3A1 Stuart).

X1s of the 4th RCB.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivative

The X1 Design

The length measurements turned out to be incorrect in the sources. As a result, all the length values were calculated and are reasonable estimates. The X1 weighed 17 tonnes (18.7 US tons) and was 6.04 meters (19.8 feet) long including the gun, had a 5.04 meters (16.4 feet) long hull, 2.4 meters (7.9 feet) wide, and 2.45 meters (8 feet) tall. It had a crew of four, with the driver located on the front left of the hull, the co-driver on the front right of the hull, the commander/loader on the left side of the turret, and the gunner on the right side of the turret.

X1s of the 6th RCB.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivative

Hull and Armor

The hull of the X1 was a lengthened and modified M3 or M3A1 Stuart hull. As such, the overall protection for most of the X1’s hull remained the same as that of the M3. The thickness of the plates which were used to lengthen the hull is unknown. The upper front plate of the X1 had an armor thickness of 38 mm (1.5 inch) at 17 degrees vertical, a middle front plate of 16 mm (0.6 inch) at 69 degrees, and a lower front plate of 44 mm (1.7 inch) at 23 degrees. Its sides were most likely about 25 mm (1 inch) thick. The rear armor and the lengthened parts of the side are unknown. Considering the original Stuart had 25 mm (1 inch) thickness on the sides and rear, it would not be unreasonable to assume that the lengthened structure was about 25 mm (1 inch) thick as well. The top plate would have been 13 mm (0.5 inch) thick and the floor plate would have gradually decreased in thickness from 13 mm at the front to 10 mm (0.5 to 0.4 inch) in the rear (although the thickness for the lengthened structure is unknown).

The rest of the X1 had a very similar layout as the Stuart. It had two headlights, one on each side of the front mudguards, two towing hooks on the front hull, and a .30 caliber hull machine gun on the right side. The driver had a two piece hatch, while the co-driver had a single piece hatch in the production versions of the X1. Depending on its variant, the X1 would either have a curved or angled rear plate, with the curved rear plate coming from the M3A1 Stuart.

X1 with a curved rear plate.
Source: https://wwiiafterwwii.files.wordpress.com/2020/09/x1preservedtanks.jpg?w=809

Mobility

The X1 was powered by a Scania-Vabis DS-11 A05 CC1 6-cylinder in-line diesel engine. This engine produced 256 hp at 2,200 rpm, giving the vehicle a horsepower per tonne ratio of 15.1. It used the same, but revised and partially nationalized, 5 speed and 1 reverse transmission and differential as the original Stuarts. The X1 had a top speed of 55 km/h (34 mph) on roads and an operational range of 520 kilometers (323 miles).

The X1 used a copied and slightly altered VVS suspension system from the 18-ton M4 artillery tractor. It had 4 road wheels divided over two bogies, with 2 bogies per track, two return rollers on each side, a drive sprocket in the front and an idler wheel on the rear. The 18-ton M4 suspension gave the X1 a ground pressure of 0.59 kg/cm2 (8.4 psi). The X1 had an on-ground track length of about 3.22 meters (10.6 foot) and could cross a trench of 1.2 meters (3.9 foot).

Turret

The production versions of the X1 used the BT-90A1 turret, which used periscopes from Vasconcelos S/A. This company had previously provided periscopes for the VBB-1 4 x 4 wheeled vehicle. The turret was armored with 25 mm (1 inch) thick steel plates at various angles to protect it from .50 caliber machine gun fire at 200 meters (218 yards). It is suggested that the overall turret layout and the internal turret construction and components were more or less copied from the French H-90 turret. It had the exact same turret ring and its overall shape seems to match the H-90. In addition, in the first BT-90 turret, a lot of equipment was carried over from the H-90, like the periscopes.

BT-90A1 rear interior.
Source: Caiafa Master – https://youtu.be/p1lUgv5eMsg

The BT-90A1 turret had a mount for a .50 machine gun on the left side of the turret, in front of the commander’s cupola. The commander’s cupola’s structure was slightly raised from the turret top to provide the commander with a 360 degree view. The antenna of the radio sets was located behind the gunner’s cupola on the right side of the turret. In addition, the X1 could mount two smoke dischargers on both sides of the turret rear, although these seem to not have always been mounted on the vehicles.

BT-90A1 rear interior.
Source: Caiafa Master – https://youtu.be/p1lUgv5eMsg

Armament

The X1 was armed with the 90 mm D-921 low-pressure gun. The low-pressure gun allowed vehicles like the X1, but also the 5 tonne AML-90 to mount a gun with significant armor penetration capabilities.

The trade-off with these types of guns is that Kinetic Armor Piercing (AP) or Armor Piercing Fin-Stabilized Discarding Sabot (APFSDS) rounds are not really worth it from a penetration point of view compared to the High Explosive Anti Tank (HEAT) rounds. A 90 mm APFSDS round for the later Cockerill guns would penetrate 100 mm (3.9 inch) of armor at 60 degrees from vertical at a range of 1,000 meters (1,090 yards), compared to 130 mm (5.1 inch) at 60 degrees for HEAT at any range. The D-921 did not even have AP rounds available for this reason.

The 90 mm D-921 gun.
Source: https://forum.warthunder.com/index.php?/topic/393523-panhard-aml-90-linx/

The X1 had access to HEAT and High Explosive rounds. The HEAT round was meant for anti-armor purposes and was the X1’s anti-tank round. The HE round was used as a general purpose support round. Another downside with these low-pressure guns was their limited combat range and decreased velocity. This meant that the gun became much less accurate at longer ranges compared to high velocity guns, which could also outrange the low-pressure 90 mm guns.

Round

Capability

Effective range

Velocity

HEAT (High Explosive Anti Tank)

130 mm at 60 degrees from vertical or 350 mm flat at any range.

1,500 meters (1,640 yards)

865 m/s

HE (High Explosive)

Lethal radius of 15 meters (16 yards)

700 m/s

The X1 stowed 18 rounds in the turret, and an additional 10 rounds in the hull, for a total of 28 rounds of 90 mm ammunition. In addition to the 90 mm, the X1 mounted a turret top .50 caliber machine gun for the commander, a coaciel .30 machine gun, and a .30 machine gun for the co-driver in the hull.

The very first X1 during firing trials in 1974.
Source: Blindados no Brasil

The X1 Family

The X1 was meant to become a family of vehicles for the Brazilian Army and, later, a potential export vehicle/conversion possibility for Bernardini. As such, the X1 has spawned many variants or vehicles which are part of its family.

X1A1

The X1A1 was supposed to be the improved version of the X1, which would fix a few of the X1’s initial shortcomings. It was further lengthened and the turret was enlarged as well. The transmission was replaced along with the brakes. Although the X1A1 meant to fix some mobility issues, it brought a new mobility issue forward. The lengthening caused the track length to vehicle width ratio to be too large, causing the X1A1 to be difficult to steer. To fix these issues, extensive measures would have had to be undertaken. Designing their own hull, in the shape of the X1A2, was relatively easier and more effective. Only one X1A1 was built, and Biselli left the X1 family project somewhere around this time.

X1A1 on the left, next to an X1. Note the additional bogie and the lengthened turret.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

X1A2

The X1A2 was the first, and up to now (2021), the only serially produced tank fully designed and mostly built in Brazil which was used in active service. The X1A2 was, in contrast to the rest of the X1 family, not built with a Stuart hull as basis, but featured a completely new design. In addition, the X1A2 was armed with an EC-90 low-pressure gun like the later EE-9 Cascavels. 24 X1A2s were built before the program was cancelled in favor of modernizing the M41 Walker Bulldog.

X1A2
Source: Image Caiafa

XLP-10

One of the planned vehicles for the X1 family was a bridge laying vehicle. Both the CPDB and the IME would design their own style of bridge laying mechanism, of which the hydraulic design from CPDB won. The bridge was 10 meter long, but it was only fit for the X1 family, which meant that the M41 could not cross the bridge. Five bridge laying vehicles were built, of which none remain.

XLP-10
Source: https://www.cibld.eb.mil.br/index.php/historico-2/blindados-eb-parte-3

XLF-40

Research on rockets started in the 1950s and, eventually, the ETE, IME, and Avibras developed the X-40 rocket. The rockets showed great potential and, as a result, in late June 1976, the XLF-40 project started its development. The only prototype was completed 2 months later. The XLF-40 project was of great importance for the company Avibras, as they gained more experience in the development of rocket systems, which would result in the ASTROS II missile system. The 40 stands for the X-40 rockets used by the vehicle.

XLF-40
Source: https://www.cibld.eb.mil.br/index.php/historico-2/blindados-eb-parte-3

XM3B1

This was a mortar carrier version of the X1, designed to resemble an M113. It mounted a 120 mm M957 mortar operated by three servicemen and a driver. The vehicle was too small to carry its own ammunition, and the force of the mortar’s blast caused the side plates of the vehicle to start bending. Only 1 vehicle seems to have been made.

The XM3B1.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

XM3C1

The XM3C1 was a recovery vehicle similar in design and appearance to the mortar carrier XM3B1, but heavier. However, its role was more akin to an engineering vehicle. It had a Munck type winch and a draw bar to haul AFV’s and remove engines. It was armed with a .50 cal. As far as it is known, only a single of these vehicles was built.

XM3C1 on the left and the XM3B1 on the right.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

XM3D1

The XM3D1 was a revival of an earlier project based on the M3 Stuart, arming an X1 hull with an M55 Maxson quad .50 caliber machine gun turret. The Maxson mount was copied by a Brazilian company and would be used for Anti-Aircraft (AA) purposes, and could mount 2 20 mm cannons as well. As far as it is known, only one vehicle was ever built. The XM3D1 found its unfortunate fate on the wrong side of a B1 Centauro barrel, as it was used as a range target when the B1 was trialed in 2001.

The XM3D1, note the angled rear plate.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

XM3E1

This was another continuation of a previous project on the M3 Stuart for AA purposes. It comprised the installation of a Bofors 40 mm L60 gun within a turret on the X1 hull. Work was initiated, and the vehicle would have a considerably lower hull than the other X1s. Because of the lowered hull, the turret had to be placed on the left side of the hull to make room for the drive shaft. Eventually the project was cancelled before the Bofors was ever mounted, and it would receive the same Maxson turret as the XM3D1. It would later be used as a towing vehicle and the Maxson turret was removed. The XM3E1 still exists at the Museu Militar Conde de Linhares.

The XM3E1 hull.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

X1P

The X1P was an overhaul of Paraguayan Stuarts which were previously gifted by Brazil. This overhaul was done for free as a sign of goodwill by Brazil and was carried out by Bernardini and the CTEx. Brazil and Bernardini hoped that this overhaul would sway the Paraguayan Army to buy the X1A2. This never happened and Paraguay would continue operating the now overhauled Stuarts. The X1P had a general maintenance overhaul and received the Scania-Vabis engine, like the X1.

The X1P.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

X-MAR

The X-MAR was part of a project from the CFN and Biselli to develop a series of vehicles for the CFN in the mid-1970s. Among these projects was a project for a tracked armored fighting vehicle, which would become the X-MAR. The X-MAR was supposed to receive a copied M41 Walker Bulldog style suspension from Dacunha Veículos e Mecânica S/A. Due to internal issues in Biselli, the projects would be cancelled, and the planned vehicles for the CFN would not come to be. Although Dacunha would try until 1980 to mount their copied M41 suspension on a Stuart, the Army would not give them a vehicle to do so.

The X-MAR sketch.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

X1 60 mm HVMS

During the 1980s, Bernardini was in negotiations with the Ecuadorian Army to convert their M3A1 Stuarts. The Stuarts would receive the 60 mm HVMS gun, which was used by the Chileans on their M50 Sherman and their M24 Chaffee. In addition, the Stuarts would be powered with a Detroit 6V53T diesel engine. Due to directive changes within the Ecuadorian Armed Forces, the project would be cancelled (potentially due to the acquisition of the EE-9 Cascavel).

X1 Bulldozer, Mine Clearing, and Ambulance

These three types of X1s were only studied and never left the drawing board, if they were actually drawn in the first place. Nothing is known about these vehicles except that they were studied for a brief while, but would never be built or further developed.

Service

Considering Brazil never went to war after World War 2, and its main issues were dealing with guerillas, the armored vehicles of Brazil have a practically non-existent combat service within the Brazilian Army.

In between 1977 and 1978, a total of 34 X1s would be delivered to the 4th RCB in São Luiz Gonzaga, Rio Grande do Sul State. The 34 vehicles equipped 2 squadrons, consisting of 17 vehicles each, and would serve for four years alongside the VBTP Urutu, until the M113 would take over this role in 1982.

The X1 and an M113 of the 4th RCB.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

In 1978, 17 X1s were delivered to the 6th RCB in Alegrete, Rio Grande do Sul State. There, it filled a single squadron, replacing the M4 Sherman squadron. It served with the Urutu as well, which would also be replaced with M113s in 1987. In addition, the 6th RCB was the only squadron to receive the X1A2, operating 10 vehicles and replacing the second squadron of M4 Shermans in 1981.

The X1A2 on the left and the X1 on the right during live-fire practice of the 6th RCB.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Throughout its service life, the X1 would show a number of issues. Most of these could be blamed on the age of the Stuart, considering the 6th RCB, which had received X1s which were converted from better quality Stuarts, had much fewer issues than the 4th RCB. Among these issues were a flawed single disc clutch, locally produced volute springs that broke and would later be replaced by imported springs, and the swing arms of the track idler starting to crack when the X1 moved at full speed.

This last issue seems to have been the most severe, as the system was apparently unable to take the weight of the X1 in combination with its speed and cross-country operations. The first instance of the swing arms cracking was in December 1979 on an X1 of the 4th RCB, after 1,570 hours of operations. This problem would also appear on X1s with as little as 200 hours of operational service. By February 1983, 8 X1s of the 4th RCB were out of operation because of this issue. By the end of 1983, only 2 of the 34 X1 vehicles of the 4th RCB would be operational.

Eventually, the problem which caused the cracking was found: the copied 18-ton suspension used a grease cup instead of oil lubrication for the bearing of the idler. Since grease has a higher viscosity than oil, it was unable to properly flow and lubricate the bearing, causing the idler wheels to get stuck and subsequently tear the swing arms apart. In June 1984, this issue was resolved by returning to oil lubrication, and the 4th RCB would operate 23 X1s after repair works were carried out. Initially, it was planned for Bernardini to produce 58 new idlers, but the costs were so high that this was abandoned.

In addition to the swing arms cracking, the hull also started to crack at the mounting point of the bogies. This was caused due to improper supporting of the bogie suspensions with the increased weight of the vehicles. Biselli seemed to not have fully committed to the X1 project at the time, which might have caused them to improperly design the mounting. It has to be noted that there was also a lack of operational and maintenance manuals, which most likely caused the vehicles to deteriorate faster than they should have.

The X1 would be gradually replaced by the M41C in 1988, and would be decommissioned in July 1994. It is suggested that some X1s were used as training vehicles, as they were cheaper than the M41C.

The M41C.
Source: http://www.lexicarbrasil.com.br

Fate

The X1s would be gradually phased out by the M41s. Most X1s seem to have been scraped, but a decent amount can still be found at multiple locations in Brazil. Various X1s ended up as gate guardians for military bases and institutions, and they are also presented in the Museu Militar Conde de Linhares alongside some variants of the X1. The X1 was never really a very good tank, with the Commander of the AMAN stating that the X1 compromises the fighting power of Brazil, and that it was more of a useful tool to get to the height of their commitments: an adequate national tank. This is really what the X1 project was. They were not particularly good vehicles, but more of a stopgap and a project to gain the experience to eventually build the vehicles that fitted with Brazil’s wishes.

Conclusion

The X1 was a more or less successful attempt by the Brazilian Army and its rising defense industry to convert an obsolete tank into a service-worthy vehicle. The X1 was the apex of the M3 Stuart, considering the X1A1 was a failure and the X1A2 was not converted from a Stuart. Brazil managed to create an extensive family of vehicles to support the X1 and all its variants for potential combat service, but only a few would ever see service, become a prototype or see the light of day.

The eventual development of the X1 might be a bit questionable, considering Engesa’s EE-9 Cascavel was, for all intents and purposes, an equal if not better vehicle. But this does not take away from the actual goal of the Brazilian defense industry at the time, which was not to create an exceptional combat vehicle. The X1 was developed and built to gain experience in the manufacture and conversion of armored vehicles, which would later be carried out on more complicated vehicles, like the M41 Walker Bulldog. The X1 just needed to extend the service life and improve the combat effectiveness of the M3 Stuart until the M41C project could be initiated. The low weight of the X1 was seen as an extra advantage, considering the infrastructure and terrain on which the Brazilian Army might have had to fight, which would have been much harder with heavier vehicles.

Nevertheless, the X1 did have some significant issues, which took some years to address. As such, the X1 can be seen as an inadequate vehicle service wise, considering that more than half of the X1 fleet was out of operation for a year until 1984, because of a problem that was first found in 1979. The X1 can be summarized as a vehicle which achieved its eventual goal from the bigger defense industry picture, but did not perform or was not necessarily much more useful than other equipment which the Brazilian Army had in service.

Illustrations

X1 converted from an M3 Stuart. Done by Brian Gaydos.
X1 converted from an M3A1 Stuart. Done by Brian Gaydos.

Specifications CCL X1

Dimensions (L-W-H) 6.04 meters (19.8 feet) long including the gun x 2.4 meters (7.9 feet) x 2.45 meters (8 feet) tall
Total weight 17 tonnes (18.7 US tons)
Crew 4 (Driver, Co-driver, Commander-Loader, Gunner)
Propulsion Scania-Vabis DS-11 A05 CC1 6-cylinder in-line 256 hp diesel engine
Suspension Bogie suspension
Speed (road) 55 kph (34 mph)
Operational range 520 km (323 miles)
Armament 90 mm D-921 low-pressure gun
.50 machine gun
.30 coaxial machine gun
.30 hull machine gun
Armor

Hull

Front (Upper Glacis) 38 mm (1.5 inch) at 17 degrees
Front (Middle Glacis) 16 mm (0.6 inch) at 69 degrees
Front (Lower Glacis) 44 mm (1.7 inch) at 23 degrees
Sides (guess) 25 mm (1 inch)
Rear (guess) 25 mm (1 inch)
Top 13 mm (0.5 inch)
Floor 13 to 10 mm (0.5 to 0.4 inch)

Turret

25 mm (1 inch) allround

Production 52 + 1 Prototype

Special thanks to Expedito Carlos Stephani Bastos, the leading expert in Brazilian vehicles, please visit his website for further reading on Brazilian vehicles: https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts and the website https://tecnodefesa.com.br, Adriano Santiago Garcia, a Captain in the Brazilian Army and ex-company commander on the Leopard 1 and ex-lecturer on the Brazilian Armored School, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near endless ability to talk about them.

Dedicated to the Brazilian Army in celebration of a hundred years of tanks in Brazil

Sources

Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., Reginaldo Bacchi
Blindados no Brasil – Expedito Carlos Stephani Bastos
Jane’s Light Tanks and Armoured Cars of 1984
Worldwide Tank Fire-Control Systems – CIA
http://www.lexicarbrasil.com.br/
Personal correspondence with Expedito Carlos Stephani Bastos
Personal correspondence with Paulo Roberto Bastos Jr.
Caiafa Master
Engesa brochures and manuals
Cockerill brochures
TM 9-785 18-Ton High Speed Tractors M4, M4A1, M4C, and M4A1C – US Army April 1952.
Stuart: A history of the American Light Tank, Volume 1 – R.P. Hunnicutt
Tecnologia Militar Brasileira magazine

Categories
Cold War Brazilian Armor

VETE T-1 A-1 Cutia

https://www.tanks-encyclopedia.com/images/drapeaux/brazil_r.jpg Brazil (1965)
Reconnaissance Vehicle – 1 Prototype Built

Up until 1967, Brazil was dependent on foreign countries for armored vehicles. Throughout and in the aftermath of World War 2, Brazil would receive large numbers of cheap armored vehicles from the United States, including the M3 Stuart and the M4 Sherman. In fact, Brazil had not undertaken any tank design since 1932, and those had only been conversions of tractors and cars into armored vehicles during the revolutions of 1924, 1930 and 1932.

Between 1932 and 1958, the Brazilian Armed Forces created a solid basis of technical institutes from which it could educate technical and research personnel, which in turn helped the Brazilian automotive industry in developing their own automotive parts and helped in opening laboratories for the manufacturers. This basis eventually resulted in a mock-up of the VETE T-1 A-1 in 1958, and later, in 1965, a prototype of the very first Brazilian indigenously designed and built armored vehicle meant for serial production. The Brazilian armored vehicle industry was born.

Development

After years of using foreign vehicles and establishing technical institutes for the army, such as the ETE (Escola Técnica do Exército, Army Technical School), which, in 1947, also provided the first specialized course in Industrial and Automotive Engineering in the country, Brazil started designing an armored vehicle. In 1958, 9 third-year students led by Major José Luiz de Castro e Silva, of the earlier mentioned Industrial and Automotive Engineering course, started designing a vehicle based on the French VP-90.

The VP-90 in Saumur. Source: https://www.chars-francais.net/2015/index.php/engins-blindes/chenillettes?task=view&id=858

The VP-90 was a vehicle designed by Victor Bouffort for the French Army in 1952. At that time, French strategists saw use in a fast tankette, and thus, Les Établissements Fouga de Béziers, which proposed the vehicle, delivered a prototype. A VP-90 armed with a 75 mm recoilless rifle was also built, but, by that time, interest in the VP-90 had been lost. The only remaining VP-90 is preserved at the Saumur Tank Museum.

During 1958 and 1959, the Brazilian students developed a concept vehicle and built a mock-up designated VETE-58 (Viature Escola Técnica do Exército de 1958, Vehicle of the Armies Technical School 1958). It was designed to be a high-speed low profile reconnaissance vehicle. Not long after, the concept was improved upon and received a predesignation VETE-T1 Cutia. Cutia was the nickname of the head of the project, Major José Luiz de Castro e Silva. However, at the time, the project would not advance any further.

Photo of the VETE-58 mock-up, released in the Correio da Manhã newspaper on January 11th, 1959. Source: Cutia, Expedito Carlos Stephani Bastos

Various companies were involved in developing the vehicle, but the most important company was FNM (Fábrica Nacional de Motores, National Factory of Engines) which manufactured about 90% of the prototype and provided the raw materials and labor. FNM was founded on June 13th, 1942, during World War 2, with the objective of manufacturing aircraft engines. In 1943, the company started producing Wright engines for the US. Brazil participated in World War 2 as an Allied country and took part in the Battle for the Atlantic and also sent an expeditionary force consisting of around 25,000 men, called the Smoking Snakes, who fought alongside the Americans in Italy. In exchange, the US would help Brazil with industry and equipment, including the capabilities of producing aircraft engines. It was seen as an advantageous contract from both the Brazilian and US perspectives. The Brazilians acquired the engine technology and learned how to manufacture them, while the US would have a supplier of aircraft engines, far away from Europe and Asia. After 1945, the production of aircraft engines was no longer needed and, in 1949, FNM decided to manufacture trucks, becoming the first automotive factory of Brazil.

Interest in the Cutia resurfaced in 1965, and IME continued the development of the 1958 VETE-58 project. A prototype was built under the responsibility of FNM. Eight companies and military institutions would eventually participate in the development of the prototype, each delivering components and design input. The prototype was built on July 13th, 1965.

Company Component(s)
FNM (Fábrica Nacional de Motores) 90% of its manufacture, engine, raw material, and labor
Arsenal de Marinha Cast-iron components
Conjunto Petroquímico da Petrobrás Rubber for the road wheels
Volkswagen Brazil Suspension torsion bars
Metalon S/A Suspension shock absorbers
SKF Brazil Bearings
CSN (Companhia Siderúrgica Nacional) Steel plates and profiles
Rio Motor S/A Technical assistance for the torsion bars

A single prototype was delivered by FNM to the Brazilian Army in the second half of 1965. When it was delivered, it received the official designation VETE T-1 A-1. The plan was for FNM to produce 100 Cutia’s for Brazilian Army units and also develop an APC version and a turreted version armed with an anti-tank gun.

Cutia prototype built by FNM in 1965, note the missing .30 cal machine gun. Source: Cutia, Expedito Carlos Stephani Bastos

The Cutia was released to the public in 1966 and, in the same year, its existence was made public to the United States Army in Volume 46 of Military Review – Professional Journal of the United States Army of July. The prototype was unarmed at first, but would later receive an M1919 .30 caliber machine gun installed on the right side of the vehicle. The later version was the version that was shown to both the public and in Military Review.

The Cutia, as presented in the Military Review journal. Note the camouflage and the machine gun. Source: Military Review – Professional Journal of the United States Army

The VETE T-1 A-1 Cutia in Detail

Advertisement in the Brazilian press on the release of the Cutia in 1966. Source: Cutia, Expedito Carlos Stephani Bastos

Hull

The Cutia was a tracked vehicle with an open hull top and was manufactured out of cold folded steel plates and profiles. The crew consisted of either 2 or 4 crew members, depending on if they sat or layed down in the vehicle. The driver was located in the front left of the vehicle and the gunner was located in the front right of the vehicle. Its armor is unknown, as Expedito Carlos Stephani Bastos, an expert in Brazilian armored vehicles stated: ‘’it was meant to ‘’protect’’ the crew from distant small-arms fire and shrapnel.’’ The vehicle was 3.6 meters long, 1.85 meters wide, and 1.12 meters tall (11.81 feet x 6.07 feet x 3.67 feet). It weighed 2.7 tonnes (2.98 US tons).

The Cutia, as presented in the Military Museum Conde de Linhares. Note the engine cover that has been opened. Source: Cutia, Expedito Carlos Stephani Bastos

The engine and fuel tank were installed in a simple steel box in the back. The gearbox was located in the front of the vehicle, which meant that the Cutia was effectively cut in half to make room for the driveshaft from the engine to the gearbox. This affected the number of crew members that could have been transported if the gearbox was located in the back of the vehicle. The box could be opened through a hinge mechanism. Furthermore, the vehicle had two headlights, two backlights, and, on the right side, above the headlight, something that resembles a blackout marker.

The rear of the Cutia in the Military Museum Conde de Linhares. Note the bronze plate which lists the names of the students who participated in the project. Source: Cutia, Expedito Carlos Stephani Bastos

Mobility

The Cutia was powered by a 4-cylinder gasoline engine that delivered 95 hp. This engine was also used in the Alfa Romeo 2000 luxury car, which was manufactured under license by FNM from 1960 to 1968 as the FNM JK, later renamed to FNM 2000, named after the Brazilian president Juscelino Kubitschek. The Cutia had a top speed of 80 km/h (50 mph) on roads and 50 km/h (31 mph) off-road. The vehicle had a 60 liter (15.85 US gallon) fuel tank and a fuel consumption of 6 km/l (0.4 miles per US gallon), which gave it an operational range of 300 km (185 miles). The exhaust was mounted on the back of the left mudguard.

The 4-cylinder 95 hp gasoline engine, located in the engine compartment. Source: https://alfafnm.com/historia-da-fnm/modelos-2/outros-veiculos-fabricados-pela-fnm/

The driver used a traditional tiller bar configuration to operate the vehicle. Another interesting detail is that the instrument panel for the driver was the same as on the FNM JK. The Cutia had a torsion bar suspension with individual torsion bars for every road wheel. The vehicle had 5 road wheels and 2 return rollers on each side. The track was very narrow.

The inside of the hull, note the tiller bars and the FNM JK instrument panel. The open box in the middle was used to store two boxes of .30 caliber machine gun ammunition. Source: Cutia, Expedito Carlos Stephani Bastos

Armament

The Cutia was armed with an M1919 .30 caliber machine gun on the right side of the vehicle. The gunner had a small vision slit above the machine gun. The vehicle had 10 boxes of .30 caliber ammunition with 250 rounds in every box, giving it a total of 2,500 rounds. In addition, it was also armed with a 2.36 inch (60 mm) M9 bazooka and had 8 rockets at its disposal. The rocket launcher was mounted on the back of the right mudguard.

Testing

The Cutia was extensively tested by the Brazilian Army. The following deficiencies came to light: the tracks were too narrow, which severely decreased the vehicle’s agility in muddy terrain, making it prone to bog down. The armor was insufficient, the engine and fuel tanks were vulnerable due to the use of gasoline, and the open-top made the crew vulnerable to weapons such as Molotov cocktails or grenades. Combined with the ease of importing US equipment and the low cost of acquiring these vehicles, these flaws would not only cause the cancellation of the Cutia project but also a decreased willingness of the Brazilian authorities to actively develop and fund their own armored vehicles until the 70s, when the costs of indigenous armored vehicle development became more viable compared to foreign vehicles.

The prototype of the Cutia is preserved at the Military Museum Conde de Linhares in Rio de Janeiro.

The Cutia without the machine gun and with 4 crew members. Colorized by Johannes D.
Source: https://shushpanzer-ru.livejournal.com/1434596.html

Conclusion

All in all, the idea behind the Cutia was not a bad idea for Brazil or any other South American country. The specifications for armored vehicles of these countries have mostly been for lighter vehicles to traverse hard accessible terrain. The Argentinian TAM tank is one of these examples. By creating a low-profile vehicle for reconnaissance, the Brazlians, in theory, could have had a reconnaissance vehicle in their army if it did not have the deficiencies it had.

The Cutia must be seen as what it was: a first attempt by an industry which had never designed and built an armored vehicle for serial production to be used by the army. The cooperation between the Brazilian Army and the Brazilian Automotive industry to create the Cutia would prove fundamental in successful future projects of the Brazilian defense industry, like the EE-9 Cascavel and the EE-11 Urutu, which all came from the industry’s humble beginnings of the VETE T-1 A-1 Cutia. It would take until 1980 for Brazil to develop a new light tracked vehicle which was meant to serve as a multipurpose platform, named the EE-T4 Ogum.

An image presenting both a truck and the Cutia built by FNM. Source: https://www.flickr.com/photos/[email protected]/33095097566/

Illustrations

The first version of the Cutia without the machine gun.
The Cutia with the machine gun.
Top projection of the Cutia.
Front projection of the Cutia.
The Cutia with a dot and stripe camouflage, based on a picture taken in 1982. The Cutia was painted in this camouflage scheme for a while when it was presented at the museum.
The Cutia painted in a multitone camouflage, this camouflage was shown in Military Review.

VETE T-1 A-1 Cutia Specifications

Dimensions (L-W-H) 3.6 x 1.85 x 1.12 m (11.8 feet x 6.1 feet x 3.7 feet)
Total Weight 2.7 tonnes (3 US tons)
Crew 2 or 4 (Driver, Gunner, 2 Passengers)
Propulsion Alfa Romeo 95 hp 4-Cylinder gasoline engine
Speed 80 km/h (50 mph) (roads), 50 km/h (31 mph) (off-road)
Range 300 km
Armament M1919 .30 caliber machine gun
M9 2.36 (60 mm) inch rocket launcher
Armor Meant to ‘’protect’’ the crew from distant small-arms fire and shrapnel, declared insufficient by the Brazilian Army.
Production 1 prototype
Special thanks to Expedito Carlos Stephani Bastos, the leading expert in Brazilian vehicles, please visit his website for further reading on Brazilian vehicles: https://ecsbdefesa.com.br/

Sources

Private Correspondence with Expedito Carlos Stephani Bastos
Blindados no Brasil, Expedito Carlos Stephani Bastos, 2011
Cutia, Expedito Carlos Stephani Bastos, 19-5-2004: https://ecsbdefesa.com.br/cutia-a-primeira-tentativa-para-produzir-em-serie-um-blindado-de-lagartas-no-brasil/
Military Review – Professional Journal of the United States Army – Volume 46, July 1966
Recorte Jornal Matéria Caminhão Guerra Chevrolet Gmc Feb
http://www.lexicarbrasil.com.br/exercito/
http://www.lexicarbrasil.com.br/fnm/
https://www.chars-francais.net/2015/index.php/engins-blindes/chenillettes?task=view&id=858
http://www.cuorialfisti.com/Speciali/FNM.htm