Category: Cold War Brazil EE-9 Cascavel

Federative Republic of Brazil (1971-1975/1976)
Reconnaissance Vehicle – At Least 9 Built + 102 Ordered

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 recognised 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 which 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.

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.

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 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.

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 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.

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.

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.

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 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.

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 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.

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.

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.

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 vehicles were all known and sold as EE-9’s.

What is interesting, is that Engesa seems to have skipped designating an M1 Cascavel, and immediately built M2 hulls after the CRM. It might be that the 37 mm Cascavels were unofficially seen as first production versions, but through hull classification were simply branded as M2’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 tyre 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
CRM	The pre-production EE-9 with a manual Clark 280V transmission and a 37 mm gun, practically an improved M8 Greyhound.	1971	8
EE-9 M2	Interestingly, Engesa seems to have skipped designating a Cascavel with the M1 designation. As a result, the production Cascavels with 37 mm guns are also M2’s. The first EE-9 to have a 90 mm gun as its main armament. Overall hull redesign, larger dimensions of the hull to mount the new 90 mm armed turrets. Used a manual Clark 280V Transmission	1974	Brazil: 157 of which at least 9 were originally armed with 37 mm. Bolivia: 24 Chile: 83 Libya: 200
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.

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 M2 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 counted as being the first 90 mm armed EE-9 M2 Cascavel. The problem is that these designs were made before the later production variant of the EE-9 was known to have been built around 1975. For this reason, these projects will be seen as prototypes for both the 90 mm armed EE-9 M2, because of its armament, and as prototypes for the 37 mm EE-9 M2 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 37 mm armed EE-9 M2, 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 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.

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 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.

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 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 had the turret with a 90 mm gun which was originally mounted on the X1 prototype. 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.

Engesa’s Entry

Engesa’s design was the turret which was briefly mounted on the X1 prototype. 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.

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 M2 37 mm

With the approval of the CRM by the Brazilian Army, 102 production vehicles were ordered. If these 102 vehicles were actually delivered is unclear. Pictures exist where at least 9 production vehicles, known as the EE-9 M2 Cascavel with 37 mm, are shown. According to statements from ex-Engesa employees, the order seems to have eventually been converted into an order for the 90 mm armed Cascavel M2 and the 37 mm EE-9 M2s were supposedly converted to 90 mm M2s. How many 37 mm M2’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 M2 was a streamlining of the CRM and mounted the final turret.

The EE-9 M2 37 mm was unofficially called ‘Cascavel Magro’, meaning Skinny Rattlesnake, while the 90 mm armed Cascavels were unofficially known as ‘Cascavel Gordo’, meaning Fat Rattlesnake.

The EE-9 M2 37 mm in Detail

The EE-9 M2 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.

Hull

The hull of the EE-9 M2 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.

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 37 mm EE-9 M2 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 M2 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 M2 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 M2 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 280V 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.

Turret

The turret of the EE-9 M2 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 M2 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.

Armament

The EE-9 M2 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 37 mm armed EE-9 M2s 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 M2 production order. By 1976, the order was probably converted to an EE-9 M290 mm order. The 37 mm EE-9 M2s were supposedly rearmed with 90 mm’s. How many 37 mm M2s were actually built and converted remains a mystery. If these 37 mm EE-9 M2’s ever were delivered to Army units and to which, is unknown. Some sources suggest that up to 50 M2s 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 37 mm M2s 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 37 mm EE-9 M2 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.

Conclusion

The EE-9 M2 37 mm seems to have been more of a stopgap than anything else. Although the Brazilian Army wanted the 37 mm armed EE-9 M2, 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 M2 37 mm 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 37 mm EE-9 M2 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

Specifications EE-9 M2 37 mm
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