Sunday 19 February 2017

Char B1 ter: Pointless Modernization

In 1936, only two years after a decision was made to put the Char B1 into production, work on its modernization began. Mostly, it entailed improving the armour and armament. In April of 1937, the first modernized tank, indexed Char B1 bis, left its Renault assembly plant. It was destined to become the most numerous medium tank in the French army, although many of its parameters put it in the heavy class. Nevertheless, even before it entered production, discussion about a deeper modernization that would create an even heavier vehicle began. This vehicle was called Char B1 ter.

At a Crossroads

The situation with the Char B was difficult from the beginning. Initially, five companies were involved in its creation (quickly reduced down to 4), as a result of which the final design ended up made of components from various vehicles. Around the time that the Char B1 began to take form, another party came into play: APX (Ateliers de Puteaux). As an aside, the distance between Puteax, the location of most of APX's plants, to Rueil-Malmaison, the location of Schneider's factory, is quite short.

APX began working on tanks in the early 1930s. Before that, its main business was artillery, small arms, and ammunition. The company got lucky in 1933 when a new turret was designed for the Char B1, indexed APX 1. A decision was made to also use it on the Char D2.

In 1934, APX designed a light tank which lost its tender, but still reinforced the company's position in the French tank market. The turret designed for this tank, the APX R, was so good that it was chosen for the Renault R35. Later, the same turret was installed on the Hotchkiss H35 cavalry tank.

It is not known when APX began to play a key role in the fate of the Char B1. In any case, by the time the tank entered production, Rueil-Malmaison was one of the main production centers. Engineer Maurice Lavirotte headed the APX design effort. According to correspondence, Lavirotte played a key role in the final stages of the design, and even during trials of the first prototypes (1931) he was referred to as "chief engineer". All further work on the Char B1 was in some way connected to this man and his design bureau.

In January of 1935, Lavitotte presented a modernization project for the Char B called Char BL. Its biggest change was that the 75 mm gun in the hull could be aimed horizontally as well as vertically. There were also sponsons with considerable armour protection. However, this proposal remained on paper.

Char BL, a draft project for a modernization of the Char B1, January 1935

Meanwhile, the military wasn't satisfied with the Char B1 just because it was put into production. Estienne's brainchild had a number of opponents who were not shy about their position. They had plenty of good reasons.

For starters, the combat mass, initially 13-15 tons and 19-21 tons in the intermediate variant reached 27 tons. Aside from the short 75 mm gun, the tank had few advantages over the Char D2. Aside from 1.5 times the weight and an impressive size, the tank had other issues.

One Char D2 cost the French army 600,000 francs, a sizeable sum, but more or less acceptable (to compare, a SOMUA S35 tank cost 982,000 francs). As for the Char B1, initially it cost 2.5 million francs, but APX and Lavirotte personally reduced the price to 1.4 million. In mass production, the price went down even further, to 1,218,000 francs. This was still an enormous sum, more than any other tank in the world.

The tank also could not be truly mass produced. With all their problems, Renault produced 50 Char D2 tanks in nine months, but needed over a year and a half to build 32 Char B1 tanks, 11 of which were built at FCM factories in the end.

The decision to make the expensive Char B1 the infantry's main tank became a ticking time bomb. It blew up in the spring of 1940 when it turned out that the French infantry does not have enough tanks.

Experimental Char B1 prototype loaded to the mass of the Char B1 ter.

General Estienne was not to blame for everything. The Armament Consulting Council (Conseil Consultatif de l'Armement, CCA for short) added fuel to the fire. The situation with the Chars D2 and B1 was reviewed at a meeting on January 16th, 1935. An opinion was voiced that it was possible to create a 20 ton tank with a 3 man crew that had analogous characteristics to the Char B1. The story of the Char G started here and finished with nothing in 1940.

At the same time, old plans for the Char B2 were dusted off. They ended up being used to create the Char B1 bis modification, but the CCA got an even bolder idea on April 9th, 1935. According to the new plan, the mass of the Char B would increase to 45 tons, its armour thickness to 75 mm. These requirements were similar to those of the Char B3. This was only the beginning of a strange project.

Intermediate Result

The CCA included enough supporters of Estienne's ideas. Among them was General Shedeville, who spoke out against the Renault FT and other light tanks, proposing that a 30-35 ton tank should be the main tank of the French infantry. He based his opinions on experience from WWI. General Velpris, known for his 600 ton superheavy tank proposed in 1923, was another supporter. Much time massed since then, and Velpris became a known theorist, as well as the Inspector-General of the armoured forces. He launched the program for a 6 ton light tank which resulted in the Renault R35 and FCM 36

Velpris initiated the program of a 45 ton Char B in December of 1935. Eventually, this program led to development of French superheavy tanks, but there was also a parallel branch.

The first Char B1 ter prototype at the factory courtyard.

Lavirotte headed the work on a "simplified" version. The company that he was working for was reorganized in the meantime. In 1936, APX was nationalized and replaced with Ateliers de construction de Rueil (ARL).

Nothing really changed, and ARL was still mostly tasked with building turrets and working on the Char B1. To aid with this, there was a mobile lab in the form of a Char B1 #101. The tank was not sent to the army, as its hull was made of mild steel, so its fate was a lifetime of trials. This tank became the starting point of the Char B1 ter program.

The same tank from the front. This photograph was the victim of retouching, which can be seen in several places, especially around the gun.

Preliminary calculations showed that it was not necessary to go all the way up to 45 tons to equip the tank with 75 mm of armour. The thickness requested by CCA was achievable at only 36 tons. As an experiment, tank 101 was weighed down to the necessary mass by thickening the sides and adding extra ballast on top. ARL engineers also tried out a new transmission on this tank, which showed satisfactory results.

The success of the first trials sealed the fate of the tank. Char B1 101 was disassembled in order to build the Char B1 ter. Some of its components were reused. Lavirotte applied all of his previous experience, including experience obtained during the Char BL project.

The sides changed noticeably.

The experimental Char B1 ter was ready for trials in December of 1937. Unlike the Char B1 bis, which was very similar to its predecessor, the new tank changed drastically. This was most noticeable in the hull. ARL engineers made calculations and decided that they could win out on weight by sloping the armour. The sides were sloped at 25 degrees and their thickness was reduced to 70 mm. The same thickness was used in the front plate. The crew's lives were hardly improved by this change, as the side hatches now opened downwards instead of sideways.

Like the Char BL, the Char B1 ter had its mudguards made of armour instead of tin. However, now there was a risk of stuffing them with mud, which could immobilize the tank if it froze. In order to improve protection, the radiator was moved from the left side to the rear.

The hull gun could now be aimed horizontally as well as vertically.

The suspension also had to be changed. Since the mass grew by 9 tons compared to the Char B1, the Char B1 ter had to use the Char B1 bis suspension, which was further reinforced. Of course, it was not possible to indefinitely reinforce a suspension designed for a tank with 1.5 times less mass, and if the Char B1 ter would enter production, there would no doubt be issues with it.

As for the engine, it was also taken from the Char B1 bis. According to calculations, the tank needed a 350-400 hp engine, but even the weaker engine attained a speed of 26.5 kph.

Char B1 ter during trials, 1939.

The armament deserves a special mention. Unkind words were periodically said about the NAEDER aiming system, as it took two men to aim the 75 mm gun. Lavirotte attempted to fix the situation with the Char BL, but his work ended at the theoretical stage. The new gun mount differed noticeably from the Char B1 and B1 bis. First, the gun could now be aimed 5 degrees to the left or right. The maximum gun elevation was 9 degrees and minimum gun depression was -4 degrees. The gun could be aimed horizontally by either the driver or his assistant. Finally, a sight was also added.

The new gun mount looked similar to the kind used in fortifications. This was both an advantage and a drawback. The size of the gun mount increased. A characteristic step in the top of the hull appeared, which reduced the driver's vision range. At the same time, the Char B1 ter lost its step underneath the gun, which was a problematic weak point.

Too Little Too Late

After the first stage of factory trials, the Char B1 ter was sent to a training center in Mourmelon-le-Grand. Trials began in April of 1938 and lasted until August 30th, 1939. The first stage of trials occurred in April-May of 1938, when the tank traveled 163 km.

Activity around the tank died down, but reignited in late 1938, then the summer of 1939. The issue was that the French army began receiving 47 mm CA Mle.1937 anti-tank guns, which could penetrate 60 mm of armour. Ideally, tanks with at least 80 mm of armour was needed. The Char B1 ter could meet these requirements, after a few changes.

A decision was made to replace the Char B1 bis with the Char B1 ter starting with tank number 715. Later, the replacement of the Char B1 bis was delayed to March of 1941 with tank number 1333. Considering the real rate of production of the Char B1 bis, these plans cause a sad smile.

This photo shows that the hatch opens downwards instead of sideways. Not the greatest decision.

One way or the other, the Char B1 ter program was relaunched. Development started on a new turret for the new tank, assigned to that same ARL. The Char B1 ter prototype had an APX 4 turret with improved armour. By the end of the 1930s, the French military was no longer satisfied with this design. ARL was working on the superior ARL 2 turret, which was originally built for the SOMUA S40 cavalry tank. Its commander's cupola was larger, and the turret was partially welded, which improved its resistance to shells. A full sized model was installed on tank #234 Marseille, after which the design continued to be improved. Unlike the ARL 2C for the SOMUA S40, the version for the Char B1 ter had 70 mm thick armour.

A diagram that explains the layout of the side plates as well as spaced armour covering the suspension.

The start of the war increased the priority of Char B1, and three prototypes were ordered at one. The first was built at ARL, the second at FCM, and the third was built by Fives-Lille, a company which specialized in locomotives and large metal construction. The military minimized participation of companies which were tasked with mass production of the Char B1 bis.

The reworked Char B1 ter was different from the original prototype. For starters, the gun mount was reduced in height, which restored the driver's visibility. The layout of the sides changed, although their slope remained. The air intakes in the rear were moved up to the engine deck.

Full sized model of the FCM turret, analogous to the ARL 2. This turret could have been used on the production Char B1 ter.

Another change was the increase of the turret ring from 1022 mm in diameter to 1218 mm. This led some researchers to believe that a two-man turret would be used on the tank. This was not the case. The turret ring diameter of the APX 1CE turret used by the SOMUA S35 was 1130 mm, and it was not two-man. Second, there was never a proposal to make the ARL 2 turret fit two people. Third, FCM proposed their turret as the rear turret for the FCM F4 heavy tank, which was definitely one-man. Anyway, this idea was cancelled rather quickly.

Production of the improved Char B1 ter prototype at ARL, early 1940. The new gun mount and increased turret ring diameter are visible.

Another piece of evidence against the fantasies of French researchers who put turrets from superheavy tanks on the chassis of the poor Char B1 ter is the AMX project. Officially this company was not involved in the Char B1 ter program, but that didn't stop its design bureau from working on a whole number of projects. One of these projects was the AMX Tracteur B, first shown on November 6th, 1939. Unlike the Char B1 ter, this was a completely new design in the same vein as tanks of various other classes designed at AMX in 1939-40.

The same tank from the rear. The improved Char B1 ter had its air intakes moved from the rear of the hull to the top.

The AMX design matched the requirements of the Char B 40, which were finalized in May of 1940. According to them, the new tank had to withstand a hit from a 47 mm gun at point blank range. The armour had to be increased to 80 mm and mass to about 40 tons. The AMX Tracteur B had all of this back in 1939. The front of the hull and turret were 80 mm thick and the sides were 70 mm thick. The suspension was similar to the one used on the AMX 38 light tank. A 370 hp Aster diesel engine was to be used, possibly turbocharged to 400 hp.

AMX Tracteur B, November 1939.

The AMX Tracteur B concept shows the logical progression of the Char B family, but even it did not have a two-man turret or a 75 mm gun in it. The turret housed a 47 mm APX Mle.1934 RF gun, with analogous ballistics to the CA Mle.1937 anti-tank gun. The turret remained with only one crewman.

As for armament in the hull, there were three variants. Aside from the 75 mm SA 35, APX proposed a 75 mm L/30 gun or a 105 mm howitzer. The last activity regarding this vehicle is dated mid-March of 1940.

The design of the AMX Tracteur B hull shows the future possibilities of the Char Battaile family.

It is unlikely that the AMX design would be built in metal, but it reflected the wishes of the French government regarding the future of the Char B. These wishes crashed and burned in May of 1940 when the war started going in a way that the French military did not plan for. Unfinished Char B1 ter prototypes from ARL and Fives-Lille factories were evacuated to Saint-Nazaire along with the experimental prototype. The tanks were loaded on board the Mécanicien Principal Carvin transport ship, which sank on June 21st, 1940 close to Royon. The third unfinished prototype remained at FCM until 1943.

The turret of the AMX Tracteur B is an answer to the fantasies of some French historians which reconstruct the Char B with a two-man turret. With a turret ring diameter of 1285 mm, this turret still only fits one crewman.

The sad story of the Char B taught the French military nothing. It's hard to explain the fact that the tank returned as the ARL 44 in 1944 any other way. It was designed by the same engineers led by Lavirotte, and the resulting vehicle was quickly reclassified as a tank destroyer. The parallel development of the AMX 45, then AMX M4, which turned into the AMX 50, brought nothing good either.

In all of these cases the issue was a customer who did not know what he wanted rather than bad engineers. Is it any surprise that the path to the AMX 30 took the French over 20 years, and the first French main battle tank had many German roots?


  1. Eh, I dunno. They had pretty sound reasons for wanting to give the hull gun some lateral traverse - aiming the whole tank precisely enough required a really delicate transmission which was the major operational Achilles heel of the B1, as it required excessive amounts of maintenance and tended to eat itself over any longer marches *anyway*.
    AFAIK the finicky Nader transmission was the single biggest cause of immobilised B1s along roadsides, and further contributed to the inability of the DCRs to respond effectively to the German breakthrough.

    As such while a bit of a case of "sunk costs fallacy" the B1 ter was arguably a reasonable enough attempt to turn the beleaguered vehicle into a more legitimately useful placeholder while more modern and sensibly laid-out designs (such as the Char G project) were still in the pipeline.
    It's not like the French were scheduling their plans in regards to the utter and ignominious SHAMEFUR DISPLAY that in the event transpired in May '40 after all...

    The ARL 44 was pretty much built just to keep what was left of the tank industry alive, though, not because anyone thought it was anything more than a stopgap placeholder. At least it had a decent gun and good frontal protection so it'd have been of *some* actual combat value had the war somehow dragged on long enough for it to participate, thoroughly obsolete as many of its technical solutions now were.

  2. Ok guys, so who's going to that sunk ship to recover the B1 Ters and restore them?