Tractor de Artillería a Orugas Yacaré

Argentina (1944-Late 1940s)
Artillery Tractor – 18 Built

Argentina’s Artillery Mover

The Ejercito Argentino sought to speed up the mechanization of its force during the later part of the Second World War. Acquisition of new foreign equipment had been impeded by the necessities of the countries at war, so the Argentine Army decided to take matters in its own hands, and devised a small family of armored vehicles, including an artillery tractor. It had modest success, but much like other armored fighting vehicles developed by Argentina during the period, it was relegated to being a parade vehicle, and would soon be phased out in favor of more modern equipment available once the war had finished.

Argentina found itself stuck in the middle of an arms embargo during the later years of the Infamous Decade of the 1930s. President Roberto Marcelino Ortiz sought to establish ties with the Allies, but his political isolation due to the fascist tendencies of the military led to the adoption of neutrality. As a result, in this period, there was an inclination towards diplomacy with the Axis powers and neutral states, such as Switzerland. Germany had long held influence on Argentina, especially in military terms, supplying its cannons since the 1890s, which helped strengthen the country against its regional rivals.

However, the Army lacked armored vehicles, being stuck with 12 obsolete Vickers mod. 1934 light tanks armed only with machine guns, along with 6 Criollo and 6 Crossley mod. 1926 armored cars. This led to the construction of a series of vehicles which included the Tanque Mediano Nahuel [Eng. Medium Tank Nahuel], the Vehículo de Asalto de Infantería Vinchuca [Eng. Infantry Assault Vehicle Vinchuca], and the Tractor de Artillería a Orugas Yacaré [Eng. Yacaré Tracked Artillery Tractor] in the 1940s. They were an attempt to modernize the mechanized forces of the Army, but also subjects of national pride and independence, experimentation in armored vehicle design, and attempts to industrialize Argentina further, which sought expansion from its old economic model, mostly focused on exporting agricultural products.

Unlike the Nahuel, another of Lieutenant Colonel Alfredo Aquiles Baisi’s designs during the 1940s, the development of the Yacaré is obscure, mostly due to the low numbers produced, without much information available. Instead, most knowledge of the Yacaré has been obtained through surviving pictures that shed some light on the design choices utilized by Baisi and the Army.

Like its indigenously-designed contemporaries in the Argentine Army, the Yacaré was named after an animal endemic to Argentina. In this case, the yacaré is a species of caiman, and while it is generally non-aggressive, it is also more than capable of harming rodents and other small prey, much like the artillery tractor that takes its name.

History and Development

On February 20th 1938, Roberto Marcelino Ortiz was elected President of Argentina after presidential elections that were tainted by fraud, part of the Infamous Decade which had begun with the 1930 coup d’état. The conservative-supported president sought to reverse the political turmoil through the use of reformist policies, opting for neutrality during the Second World War and engaging in protectionism to strengthen the Argentine industry. His presidency was hampered by health issues caused by type 2 diabetes and distrust of his liberal tendencies from his conservative colleagues. In 1940, Ortiz left the presidency in the hands of his vice president, Ramón Antonio Castillo, who, while seeking a return to conservative policies, continued the industrialization supported by his predecessor. Ortiz resigned on June 27th, 1942 due to blindness caused by his condition, followed by his death less than three weeks later, on July 15th, 1942.

On October 9th, 1941, with Ramón Castillo acting as president, Ley 12.709 [Eng. Law 12.709] was passed, arranging the creation of an indigenous military industry under the Dirección General de Fabricaciones Militares (DGFM) [Eng. General Directorate of Military Fabrications]. It was given control of military ordnance planning, mines to extract resources from, and the capacity to produce AFVs, small arms, and munitions. It would be responsible for the creation of the Nahuel tank, the Vinchuca troop transport, the Yacaré artillery tractor, the ALAM.1 machine gun, the FMK-3 submachine gun, the FARA-83 assault rifle, and the 75 mm and 105 mm Czekalski series of recoilless rifles.

Baisi had already been involved in the conversion of a few unspecified agricultural tractors into Vinchuca armored vehicles, which made him, in the eyes of the Army, the best candidate to create designs for the nascent industry. In 1943, along with Major Francisco A. Villamil and his team, Baisi received the task of designing a 35 tonnes medium tank. Forty-five days later, the team built a 1:1 wooden mock-up, designated “251”, of the future Nahuel tank.

The Yacaré appears to have been conceived around the same time as the Nahuel. Both the mock-up of the Nahuel and the Yacaré utilized the same model of tractor as a base, being the chassis chosen for experimentation by the Argentine Army, of which 30 models were imported. Taking into account the Vinchuca’s use of agricultural tractors for conversion into AFVs, it is also possible that the Yacaré was based on the design of the Vinchuca.

The modification of the tractor was carried out in the Esteban De Luca Arsenal in San Cristóbal, Buenos Aires, and according to archives 18 were produced, with known serial numbers “R 81”, “R 82”, and “R 83”. The Yacaré was revealed to the public in an Army Exposition on June 4th, 1944, along with the Nahuel. There are pictures available of the same Army Exposition where the Nahuel and Yacaré were displayed to the public.

However, there are sourcing issues with the date of the exposition, given that there are some misdated pictures of a parade that would have taken place on the same day. The Nahuel models shown in the parade are of a later type that lacked two of the glacis-mounted machine guns and featured a new vision block for the driver, introduced around 1947, during the first presidency of Juan Domingo Perón.

The reason for this mistake is the scarcity of images on both vehicles, as Nahuel pictures are rare, and those of the Yacaré even more so. The parade happened during or after 1947 and the modernization of the Nahuel tank. The Yacarés also participated, towing 20 mm Oerlikon autocannons. Interestingly, during these events, no Vinchucas were apparently present, which had most likely already been scrapped or modified into Yacarés before they were shown off to the public. These are the last known whereabouts of the Yacaré, as after this parade, they faded into obscurity.

Alfredo Aquiles Baisi

Lieutenant Colonel Alfredo Aquiles Baisi was a second-generation Italian immigrant born in 1902, the son of Captain Adolfo Vincenzo Baisi, an officer in the Royal Italian Army, and his wife, Carlota Allende. His brother was Oscar Baisi, who entered the Argentine Navy.

Adolfo Baisi was born in the latter half of the 19th Century in Alvito, Italy. He graduated from the Accademia Militare di Modena [Eng. Military Academy of Modena], and enlisted in the Royal Italian Army, being promoted to the rank of Captain. Attracted by America, he emigrated to Uruguay, where he would work as a Professor of Mathematics, Greek, and Latin. When he arrived in Buenos Aires, Argentina, Adolfo Baisi joined the Argentine Army and revalidated his rank as Captain, working as an Artillery and Ballistics Officer, introducing mathematics and statistics into his discipline. In Cordoba he met Carlota Allende, marrying her and having two children. He remained in the Army for years before retiring and ending his career as a professor in the Colegio Militar de la Nación [Eng. National Military College], with the rank of Lieutenant Colonel.

Alfredo Baisi followed in his father’s footsteps, with the first recorded event of his career being his role as a military attaché for the Argentine Embassy in the USA. He introduced indirect fire into the artillery units, and designed the outfits for Argentine Army tankers and infantry in 1935. German influence permeated the Argentine Army since the early 20th century, determining political affiliations, weapons, uniforms, and parades, which reflected in his own choices for the newly-made uniform, which sported Stahlhelm-style helmets and tunics inspired by the summer Wehrmacht outfit.

Baisi’s power began to grow, and he represented his country in the Inter-American Defense Board, created on March 30th 1942, with Argentina as a founding member. He held the position of director of Arsenal Esteban de Luca and Subsecretario de Industria y Comercio [Eng. Under Secretary of Industry and Commerce]. He also became Interventor de la Dirección Nacional de Vialidad [Eng. Interventor of the National Traffic Direction], which gave him the task of examining documents, accounting books, and inventories to inform the Tribunal de Cuentas [Eng. Court of Accounts], which had the task of approving the DNV’s budgets.

Baisi was one of the original founders of the GOU or Grupo de Oficiales Unidos [Eng. United Officers’ Group] alongside Juan Domingo Perón, which overthrew Ramón Castillo’s presidency in the country’s second coup d’état in 1943.

By 1944, Baisi held the rank of lieutenant colonel and had opposed Perón, who was not yet president, when he decided to cut diplomatic ties with the Axis powers. This disagreement led to Baisi’s support of Colonel Luis César Perlinger, along with a few officers, in a power struggle with Perón for political leadership in anticipation of the next democratic period in Argentina. The incident led the Peronist government ordering his retirement from the Army in 1950 before he could be promoted to general.

During the next years, he was involved in scientific magazines as a publisher and researcher, developing a calculator for indirect fire for the Argentine artillery. He passed away aged 73 in 1975. He had one son, also named Adolfo Baisi, who worked as an engineer.

Design

The vehicle was fully tracked, based on the TD-35 tractor produced by the International Harvester Company from 1937 to 1939, of which the Argentine Army acquired 30 units.

The TD-35 weighed 4.785 tonnes, and the Yacaré was significantly heavier, at 8 tonnes. Unlike contemporary tractor-tank designs, the design was not crude, and it was composed of welded armor plates, indicating that it was not an improvised vehicle, and of superior quality to comparable designs, such as the Sutton Skunk. The only exceptions were the armor plates, which included the front grill, which were riveted to the side plates.

The suspension was also armored with a side skirt, the sides had ventilation grills for engine cooling, while the roof was open-topped. The absence of an exhaust on top of the tractor is noticeable, which indicates that it was either cut off or repositioned elsewhere. It was equipped with a trench-crossing roller in front of its tracks and two headlights placed in front of the machine guns, the same model the Nahuel used. Similar to the Nahuel, which had a jaguar design on its hull’s side, the Yacaré had a yacaré caiman painted in a similar position.

For the crew, there was a seat for the driver in the center and two seats to the sides for machine gunners. It could tow an Oerlikon 20 mm L/70 on a two-wheeled trailer. It is possible it would have been able to carry heavier armament, for example, the Bofors 40 mm L/60, which had been available since 1938 and was shown off in the June 4th Exposition.

Armor

The TD-35 was initially produced with a metal shell that would have provided inadequate protection for an artillery tractor, instead, the Army chose to upgrade it with a new armored hull, which gave extra protection to the crew and the engine. Unlike the earlier Vickers mod. 1934 tank, it was almost fully welded, and changes were done to enlarge the body of the tractor and widen it, with the tracks sitting below the hull. The front had a flat, exposed grill riveted to the side armor, with the driver’s cabin and the machine gunners being protected by a sloped sheet of armor, angled at 45°. This is where armor would have been the thickest, at 12.7 mm. This meant that at best, it had 18 mm of line-of-sight armor thickness, which would have protected the crew from small arms fire.

The sides were flat, with grills covering the engine area, and the side skirts were close to the same thickness. The crew was exposed, but considering the tractor’s role as an artillery mover, this was not much of a problem. The back was where armor was thinnest, at 5 mm or even thinner.

The entire up-armoring of the Yacaré, minus the machine guns, which weighed 10.5 kg, added 3.194 tonnes, which seems to confirm that the armor was no thicker than 10 mm. This did not protect the open front grill though, which would have been very vulnerable to enemy fire. Even so, the rest was merely shrapnel and small arms fire resistant.

Mobility

As the Yacaré was a modified tractor, it kept the same transmission as the TD-35, an International Harvester Torque Amplifier. The sliding gear transmission had 6 gear shifts, 5 forward and 1 reverse, with the five-speed ratios, in order, being 1.8, 2.3, 2.8, 3.3, 4, and for the reverse, 2.3. The tracks were relatively wide for a tractor of its size, 16 inches or 40.64 cm in width, decreasing ground pressure and allowing it to withstand the extra weight of the armor, weaponry, and crew.

The engine was an International Harvester diesel engine, with 4 cylinders, 6.8 l of displacement, liquid cooling, 49.2 l of coolant capacity, and an overhead valve design. Its output was 42.2 horsepower at 1,100 rpm, with 37.09 drawbar horsepower, and it allowed the TD-35 to tow a load of 3739 kg, easily enabling it to tow the larger Bofors 40 mm L/60, weighing 522 kg, and the Bofors 75 mm L/40, weighing 1,435 kg. Even with the added weight of the Yacaré armor, it was an effective artillery mover for the Argentine Army’s needs, only struggling with the largest artillery pieces at their disposal, such as the Schneider 155 mm L/30 mod. 1928.

While the TD-35 was outfitted with return rollers, it appears to have had an unsprung suspension, which did not do much to help its off-road capabilities, and while the Yacaré’s could have been improved from the TD-35, it is rather unlikely that it was worth the effort. The power to weight ratio for a TD-35 was 8.82 hp/tonne, and the top speed would have been low, around 20 km/h. The Yacaré was heavier and the power to weight ratio would have been a rather poor 5.28 hp/tonne, lowering the top speed even further.

Armament

The gunners to each side of the driver were provided with one Madsen 11.35×62 mm machine gun each for anti-infantry use. The Madsens were already used by the predecessors of the Argentine Air Force in their Curtiss H-75O Hawk fighters and Ae.MB Bombi light bombers. It was an enlarged version of the regular 7.65 mm Madsen machine gun, fitted with spade grips and belt fed, as used in the Yacaré, but there were variants fitted with regular box magazines.

The 11.35 mm Madsen machine guns gave the Yacaré a limited anti-tank capability. Nonetheless, they were helpful against the limited armored forces of Argentina’s neighboring countries, of which the only tank that offered enough protection from the Madsen at all ranges at the time was the LTP in use in Peru. It had a cyclic rate of fire of 900 rpm, a barrel length of 750 mm, and a weight of 15.9 kg when fully loaded with 100 rounds of 11.35 mm ammunition.

Kynoch was the main manufacturer of 11.35×62 mm ammunition through most of the Madsen’s service history with the Argentine Army, but from 1940 to 1946, it was manufactured by the Fabrica Argentina Militar de Municiones y Armas Portátiles [Eng. Argentine Military Factory of Munitions and Firearms], which would later be integrated into DGFM. Two million rounds of ammunition were produced by FAMMAP, of which there were Ball, Armor Piercing, and Incendiary Tracer variants. The shells weighed 19.83 g, and they were fired at a muzzle velocity of 850 m/s. Using AP rounds, it had a penetration of approximately 20 mm of RHA at 10 m.

Madsen HMG (11.35×62 mm)
Projectile and Type	Velocity	Weight	Filler	Fuze	Penetration (10 m at 0°)
Ball	~850 m/s	19.76 g	None	None	Unknown
AP	850 m/s	19.83 g	None	None	20 mm
I-T	~850 m/s	19.76 g	5.76 g	None	Unknown

The Oerlikon 20 mm L/70 mod. 1938, the only artillery piece seen towed by the Yacaré in pictures, can easily be confused with the Bofors 40 mm L/60 mod. 38 also obtained around the same time, but the 20 mm cannon was much smaller and manned by one crew member instead of two. Switzerland donated 175 cannons to Argentina, which were of the earlier Oerlikon SS variety. Strangely, the only images in this time period of the Oerlikon that have survived were the ones in which it was towed by the Yacaré.

Chambered in 20×110 mm RB Oerlikon, the gun had a cyclic rate of fire of 450 rpm, weighed 68.04 kg, and had a muzzle velocity of 820 m/s. While ammunition was produced by Argentina for the cannon, it was only produced from 1972 onwards, so all rounds utilized in the 1940s were foreign-made. Due to the Allied embargo put in effect against Argentina, the sources of ammunition were either Swiss or German. It is possible armor-piercing rounds were provided, and the projectiles weighed between 232 and 250 g.

Vinchuca

Before the Nahuel and the Yacaré were completed, a predecessor was designed, also built by Baisi, the Vehículo de Asalto de Infantería Vinchuca [Eng. Infantry Assault Vehicle Vinchuca]. It followed the same idea as the Yacaré, designed as an infantry carrier based on an agricultural tractor. Sources vary on the model of tractor utilized, with candidates being “English tractors”, the TD-35, or impossibly, the Nahuel chassis, which at the very least would not be manufactured until two years later. Due to the TD-35’s use as a Nahuel mock-up, it was likely the tractor model used as a base. Other rumors suggest that it was equipped with the same Madsen machine guns, or even mounted the Oerlikon 20 mm.

No images seem to have remained of the Vinchuca, but there is an outlier to the 18 Yacarés manufactured. Unlike the rest of the Yacarés, “R 83” does not appear to have headlights, Madsen machine guns, or the yacaré painted on its side. Whether it was still ongoing construction or not is unknown, but as its serial number and the Argentine roundel were already painted on, the lack of any animal appears to point towards being an earlier version, possibly even a prototype Yacaré or a Vinchuca awaiting conversion into a Yacaré.

Conclusion

The Yacaré did not survive for long, as it was discarded in favor of newer, more powerful M4 High Speed Tractors purchased extremely cheaply by Argentina after the Second World War. It was a step in the right direction for a nation that did not have an industry strong enough to manufacture more modern equipment, and for all its faults, it was a worthy effort, although overshadowed by the more successful and recognized Nahuel.

Unfortunately, the brief period of stability in the country could not last, and with Baisi stepping away from his role in AFV design, the following years, further affected by Juan Domingo Perón’s lack of experience with industrialization and protectionism, led to an early death for the Argentine tank industry. It would be decades later, in the 1960s, when Argentina picked up the idea of building indigenous AFVs again, and even more time would have to pass until Argentina began the construction of vehicles capable of moving artillery, with the TAM VCA built in 1990.

There are no records of the Yacaré’s performance or its use apart from the publicly shown parades and expositions, but from what information is available, it most likely fulfilled its role well, being able to move the artillery pieces and anti-tank guns the Argentine Army had at its disposal at the time effectively. However, the mobility issues from the up-armoring and the underpowered engine would have made its use complicated for the Army. In addition, it might not have been able to carry its own ammunition, and might have been unable to carry additional crew if it had to tow any cannon other than the Oerlikon. The Oerlikon 20 mm cannons saw use far after being taken out of Swiss service, with Argentine 20×110 mm RB ammunition being manufactured as late as 1981.

Sources

Ricardo Jorge S. Fogliani, Blindados Argentinos, de Uruguay y Paraguay.
DIA, Small Caliber Ammunition Identification Guide, Volume 2, 20-mm to 40-mm cartridges.
Ricardo Jorge S. Fogliani, Nahuel DL 43.
Georg V. Rauch, El Tanque Nahuel DL-43.
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Yacaré Specifications
Dimensions (L-W-H)	3.66 x 1.52 x 1.22 m (12.00 x 4.98 x 4.00 ft)
Total Weight, Battle Ready	8 tonnes
Crew	3 (Driver and 2 Gunners)
Propulsion	International Harvester diesel engine, 4 cylinders, 42.2 hp at 1100 rpm
Speed	Roads: Around 15 km/h
Range	Unknown
Power to weight ratio	5.275 hp/tonne
Suspension	Unsprung
Transmission gearing	5 forward (1-2-3-4-5): 1.8, 2.3, 2.8, 3.3, 4.0 1 reverse: 2.3
Fuel capacity	151.4 L (40 gal)
Ground clearance	Unknown
Trench crossing capability	Around 2 m (est.)
Armament	Primary: Oerlikon 20 mm L/70 mod. 1938 Secondary: 2 x Madsen 11.35 mm HMG
Elevation and traverse	(Madsen HMG) 70° traverse (est.), 0 – 80° elevation (Oerlikon 20mm) 360° traverse, -5 – 87° elevation
Gunsight	Mechanical/Iron Sights
Ammunition capacity	Unknown
Armor	12.7 mm
Communication	None
Production	18