Wednesday, 20 January 2016

Third Reich Serving the Fourth Republic

After the end of WWII, French tank design was significantly influenced by their German colleagues. Their achievements are very well reflected in the design of the French AMX M4 heavy tank, the predecessor to the AMX 50. Even though the tank never reached production, it left its mark on tank building history. Here's how it all began.

Despite the occupation of France, French tank designers did not stop for even a minute. Work continued in strictest secrecy on both new tanks and modernizations of existing ones. Most progress came from Ateliers de construction de Rueil (ARL) from Rueil-Malmaison, west of Paris. In addition to an array of pre-war tanks, they also designed the SARL (Somua-ARL) 42 tank in 1942. In November of 1944, ARL began designing a heavy tank with experience of the SARL 42 and B1 ter tanks in mind. The designs of German tanks, especially the Tiger II, was also kept in mind. The first ARL 44 prototype was built in 1946.

The French military knew that this vehicle was only a temporary measure. Rapid developments in the field of armoured warfare rendered the ARL 44 obsolete even during its design phase. The suspension and design of the hull were more suitable for the early 1930s, maybe even mid 1920s. Neither 120 mm of front armour nor the Maybach HL.230 engine could bridge the gap. The military decided to keep the project open, but a competition for a new 50-ton medium tank began on July 31st, 1945. ARL did not participate, as work on the ARL 44 was in progress.

According to archive data, the following companies participated: Forges et Chantiers de la Méditerranée (FCM), Ateliers de construction d'Issy-les-Moulineaux (AMX), Lorriane, Somua, and... Renault. The last entrant is the most curious, especially since AMX was essentially the tank branch of Renault, nationalized in 1936. Aside from the fact that Renault participated in this contest, no information survives to this day; work did not even reach the project stage. FCM was also unlucky, and its 50 ton tank remained on paper. After more than 5 years of work, Lorraine and Somua produced prototypes of their projects (Lorraine 40t and Somua SM). Work got as far as designing and producing prototypes of SPGs on the Lorraine 40t chassis.

AMX was the luckiest. This company from suburban Paris worked on its 50 ton tank for almost 15 years, the project was changed several times, and SPGs were designed and built on its chassis. The tank never made it to mass production, but deserves a spot in history.

The characteristics of the AMX tank were similar to those of the ARL 44. The vehicle, indexed Char A.M.X. 45, was also referred to as NOM 141 (project 141). It was supposed to have 120 mm of front armour (50 mm LFP), 50-60 mm thick sides, 110 mm of front turret armour, and 30 mm thick turret sides. Like the ARL 44, the cast turret designed by DEFA (Direction des Études et Fabrications d’Armement, later reformed to GIAT, renamed Nexter in 1989) would house a 90 mm 65 caliber long Schneider gun with a coaxial 7.5 mm MAC Mle. 1931 machinegun. Another machinegun was placed in a ball mount in the front of the hull. The 47 ton tank would be put in motion by a German Maybach HL.230 engine. The tank looked like a Tiger II from the outside, but the French refused to place the transmission in the front. The transmission and drive wheels were in the rear from the very beginning of the project.

The first draft of the AMX 45 project is dated August 1945. By the end of the month, the project was radically altered for the first time. The new characteristics drove up the mass by 3 tons, to a total of 50 tons. The Maybach HL.230 was no longer satisfactory, as 700 hp was considered too little for such a heavy vehicle. High effective horsepower was considered very important, based on experience from WWII. Starting with blueprint 01041 dated August 28th, 1945, the tank obtained a 1000 hp MP.65 Sauer engine. The AMX 45 index disappeared, replaced by a new one: Char Moyen 50t M4 (50 ton medium tank M4). The name "AMX M4" stuck for five years, during which the project changed almost completely.

The Swiss engine didn't last long. It was not available in metal, and the engine is no less an important component of the tank than its gun. Not surprisingly, the Germans replaced the Swiss in this regard. Maybach ended up under French influence after the war, and mutually beneficial cooperation followed. Also, many German engineers, including Porsche, ended up involved with French tank design, willingly or otherwise.

If ARL 44 was the combination of existing components, the AMX M4 was a combination of all German late-war ideas. The E-50 and E-75 that are so beloved by fans of alternate history left their mark here. Recall that the E-50 was meant to have a rear transmission, and the Maybach HL.234, proposed as the power plant for the E-50 and E-75, evolved into the new AMX M4 engine. The HL.295, blueprints for which are dated September 1945, was an enlarged HL.234, giving 1000 hp at 2800 RPM. This was not just a proposal, it was really built in metal. Maybach engines also powered the Lorraine 40t and Somua SM tanks. As for the AMX M4, the HL.295 first appeared in its design towards the end of November of 1945.

By then, the AMX M4 began another metamorphosis. The turret was unchanged, but the hull and its interior changed drastically. The front plate was thinned out to 90 mm, the sides to 40 mm, but the slope of the UFP was increased from 42 to 55 degrees. The hull became more reminiscent of the Tiger II, but with the turret further forward. This introduced many problems with the hatches for the driver and hull gunner. It was decided to make them smaller and put them in the corners of the roof. The driver received an observation device similar to the one on the Panther Ausf. D and Ausf. A.

The AMX M4 kept changing in the winter of 1945-1946. One of the changes moved the crew around in the turret. Initially, the commander's cupola, essentially a copy from the pre-war AMX Tracteur C, was to the right of the tank. In December of 1945, it, like the Tiger II cupola, was moved to the left, increasing the resemblance of the two tanks.

The changes to the hull, or rather the suspension, were more interesting. Designers realized that torsion bars are a very non-French solution, real French tanks use bogeys. They were presented as an alternative to the torsion bars. Not one, but two alternate designs were made.

The first variant was a re-imagining of the work of Surin, used on CKD tanks. While Surin used large wheels, the wheels here were much smaller than the ones in the torsion bar variant. Leaf springs were used, a bold move considering the mass of the tank. Since there were seven wheels per side, the front wheel received its own spring. Return rollers had to be added, four per side. The idler was also changed, and its tightening mechanism was very reminiscent of the good old Char B.

The other bogey design used the same idler. This variant had five return rollers, and the first and last were smaller than the rest. The number of road wheels grew to eight, so no individual suspensions were needed. Clearly there were some engineers that worked on tanks in the 1930s, as the suspension was taken straight from the Renault R35 and other light tanks of that era. Paired springs were used instead of rubber elastic elements; this design was a lot more progressive.

Both bogey designs were rejected. Yes, torsion bars have their difficulties, and yes, Kniepkamp's suspension has its problems, but compared to what AMX engineers came up with, it was the height of perfection. Not only was the bogey suspension inappropriate for such a heavy tank, it turned out much more complicated. It is hard to imagine what kind of curses French tankers would utter if they encountered this design in production. The alternative idea failed.

By early 1946, the new Char M4 was finalized. It was an interesting fighting vehicle, similar to the Centurion Mk.3 in characteristics. This tank, officially designated as medium, weighed 50.8 tons, but managed to surpass the French design only in the thickness of turret and side armour. The Centurion had less effective hp/ton, and was more than half a meter longer. The guns of the two tanks were similar. The American M46 Patton also had similar characteristics. With an 810 hp engine at 44 tons, it came close to the French tank in mobility. Aside from the sides, the armour of the two tanks was similar. The American tank was taller than its competitors, and also longer than the French tank. The product of Ateliers de construction d'Issy-les-Moulineaux was a rather ordinary tank, very much in line with the international idea of a medium tank at the time.

A year later, the M4 was once again radically redesigned, but more about that next time.

Read the next article in the series.
Original article by Yuri Pasholok.

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