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WW2 French Prototypes

ARL 37 ‘Char de Rupture’

France(1937)
Heavy tank – none built

The 1930s was a period of rapid re-armament and tank development. Many European nations were focusing on developing and improving their own tank forces, leading to more and more specialized and advanced fighting vehicles. France was not to be left behind, reorganizing part of its defense industry and starting new tank projects. The need for a new French heavy tank was amplified with the start of the construction of the German Siegfried Line, a defensive wall running across the German border with France, vis-a-vis the Maginot line.

This prompted the French Conseil Consultatif de l’Armement (Armaments Advisory Council) on 4th May, 1936, to start a new heavy tank program. The technical requirements for the new tank, named “Char de Rupture 1937” (roughly translating to breakthrough tank), were released on 12th November 1936. The Conseil Consultatif de l’Armement stated the following:

“Char lourd, très protégé et très armé, propre en particulier à être utilisé défensivement et offensivement dans la guerre en région fortifiée”.
(Eng: “A heavy tank, well armored and well-armed, suitable for both defensive and offensive purposes in fortified battlefields.”)

The main focus was the armor and armament. In Char B1 fashion, there were two main armaments, one in the hull and one in a fully rotating turret. The armor was to be able to resist anti-tank cannon fire from as close as 200 meters (220 yards). In addition, the top speed was requested at 30 km/h (18 mph) and a range of 200 km (125 miles) or 10 hours. The total weight was to not exceed 45 tonnes (49.6 short tons)

In the spring of 1937, three French companies presented their designs: AMX, FCM and ARL.

Ateliers des constructions de Rueil

ARL was the only company that had not designed tanks before. In 1935, the Docks de Rueil, originally part of APX (Ateliers des constructions Puteaux) were renamed to Ateliers des constructions de Rueil (abv. A.R.L.) after nationalization. It was also then that the design bureau was created. Located in the suburbs of Paris, the workshop became more famous post-war, with the construction of the ARL 44, yet participated in the design of many other French tanks.

Triplets

Unlike its competitors, which presented the AMX 37 and FCM F4, ARL presented three designs simultaneously, the Variant C, Variant S and Variant V. Every version had different turrets, armaments and layout. It is important to note that blueprints of the rear of the hull do not exist. It is unknown if they were ever made or potentially lost, however, all the existing blueprints are on the armament layout, showing that they were supposed to use the same hull. Ultimately, the engine used and similar details are unknown. All three variants were, speculatively, based on the same hexagonal-shaped hull, with large tracks running over side skirts, similar to the Char B1. In addition, all versions had a flamethrower mounted in the hull, on the right side, to compensate for potential blind spots.

75 mm APX howitzer model 1929

The gun used inside the hull was the 75 mm APX howitzer mle 1929. Originally made for the Maginot Line as a static defense, it was developed from the infamous Model 1897 75 mm howitzer. It was later adapted for use in armored fighting vehicles and used in the later ARL V39 prototype. This gun was also used by the other competitors, FCM and AMX.

Side view plans of the gun mount in the ARL 37 (in this case, Variant C). The driver was also the gunner, as he had to traverse the entire tank to aim the gun, since it only had 5° of traverse. This arrangement was also present on the Char B1. Elevation and depression were better, at +18°/-15°.

Variant C

The most simple (from a mechanical and design perspective) out of the three, Variant C, was very similar to a Char B1 Bis. Besides the hull-mounted gun, a 1-man turret was mounted on the left side of the hull roof. The turret was very similar to the APX-1 turret on the Somua S35 and Char B1 Bis, however, the armor was greatly improved, at approximately 100 mm (4 inches) all around. Inside the turret, a 47 mm SA35 gun was mounted, the same gun as on the Char B1 Bis and Somua S35. The ammunition used would have most likely been the same Obus de Rupture Mle 1935 (AP model 1935) weighing 1.62 kg (3.6 pounds). The entire shell was 325 mm long (13 inches) while the projectile was 145 mm long (5.7 inches) and the case was 193 mm long (7.6 inches). On the Char B1 Bis, the muzzle velocity of the SA35 was 660 to 680 m/s (22 feet per second) with a penetration of 40 mm angled at 30° at 400 m. Variant C carried 106 rounds of ammunition for the 47 mm, 98 in the hull, and 8 in the turret.

It had a crew of four, a driver, responsible for driving the tank, but also aiming and firing the 75 mm gun. Behind him in the hull was the loader of the 75 mm gun. In the turret was the commander, responsible for commanding the tank, spotting targets, loading, and firing the 47 mm gun. This was a common feature of French tanks of the period. At the end of the crew compartment, a mechanic was seated. Quite common on WWI tanks, this position was archaic by 1937 standards. In practice, he would have been in charge of passing ammo up to the commander and fulfilling other, smaller tasks. He would have also been in charge of the radio, of unknown type, yet it is likely to have been the ER-53, used on Char B1s.

Side views of a SA35 gun from a B1 Bis tank. Source: Warspot
Side view of the crew compartment of the ARL 37 Variant C. The thick armor and crew layout can be seen.
Source: Chars Francais
Top view of the ARL 37 Variant C. The similarity to the Char B1 Bis is discernible.
Source: Chars Francais

Variant S

The second design proposed was more complex than the previous, and the plans available are even more scarce. The small turret was replaced with a larger, three-man turret. However, this increased the crew to six men. The turret was cast into a large octagon, still with 100 mm thick sides. In contrast to Variant C, it was equipped with a 47 mm mle 1934 gun, which was also designed for use on the Maginot Line. It fired APX mle 1936 Obus de Rupture (Armor-Piercing High-Explosive, APHE) shells, with a muzzle velocity of 880 m/s and could penetrate 77 mm (3 inch) of armor angled at 30° at 500 m (547 yards) and 56 mm (2.2 inch) of armor at 1,000 m (1,094 yards). The shell weighed 1.670 kg (mock warhead, translation from the French “fausse ogive”) and the charge weighed 610 g. It is hard to tell why two different guns were chosen for different designs.

The main turret had a smaller, rotating pseudo-turret or cupola for the commander. This was equipped with two machine guns, most likely 7.5 mm MAC 31, however it lost the machine gun mounted parallel to the main gun, like in the Variant C. The commander would now stand in this cupola and be able to more effectively scan the environments and engage infantry.

As the crew expanded to six men, the layout changed. The turret now had a designated commander, gunner, and loader. Meanwhile, inside the tank, the driver, loader, and mechanic were the same. The designated gunner and loader would have vastly increased the efficiency of the tank. However, these changes would have made Variant S vastly more expensive compared to Variant C.

Side cutout view of the Variant S turret. While the majority of the turret was still 100 mm thick, the cupola was thinner.
Source: Chars Francais
Top view of the Variant S turret. The much larger size of the turret is obvious, most likely taking much of the space on the hull roof.
Source: Chars Francais

Variant V

The most complex and interesting of the three designs was Variant V. The turret was now unmanned and was equipped with a 47 mm SA35 (same as on Variant C) and two 7.5 mm MAC machine guns mounted coaxially, on each side of the gun. As it was unmanned, it was made much smaller. To aim and fire it, a device was created by Lorfeuvre, that would allow the commander to aim and fire the guns in the turret, and even the 75 mm in the hull, from a dome-like casemate to the right of the 47 mm turret. To cover up the blindspot that was created by the casemate, an additional 7.5 machine gun was added, facing the rear.

The crew was now five men. There was a driver (it is unclear if the 75 mm howitzer could be aimed and fired by both the driver and the commander) and two loaders, one of which was also designated as a mechanic. They shared the task of loading the 47 mm and 75 mm. Despite being unmanned, the turret did not have an autoloader, the technology did not exist in 1937. Rather, the loader was underneath the turret and loaded from there. The commander was located in the dome-shaped casemate and the radio operator was on the right of the tank, “inside” the side skirt in between the tracks.

Cutout side view of Version V. The small unmanned turret and large, dome shaped casemate can be seen. Note the gas canister for the flamethrower in the bottom right.
Source: Chars Francais
Top view of Version V. The crew positions are clear, however how the two loaders (the two men sitting in line behind the driver) operated is hard to tell. Most likely, one passed on the ammunition, while the other loaded. Yet the interior seems roomy, so they could move around more in combat. The location of the radio operator, inside the track side skirts, gives information on the mysterious hull design. Since there was enough space to fit a man inside, it means the suspension most likely used leaf springs. Coil springs would be too large, like in the AMX 37, where the coils took up the whole height of the sideskrit.
Source: Chars Francais

Version V was a very unorthodox design, clearly being expensive and more complex than the other variants. The ARL 37 would have been extremely expensive no matter what, its undoubtedly large size, thick armor, and need for a massive engine would have made this program very expensive, let alone the complex devices needed on the Version V.

Hull

The largest mystery with the ARL designs remains the hull. Since no complete blueprints exist, it is hard to tell how it looked. From the existing blueprints above, we do get a clear image of how the front looked, and that it had small, leaf spring suspension, like many other French tanks of the time. The rear of the hull was never designed, as it included the engine, transmission, and other parts that did not exist and would be subject to change. Nonetheless, the ARL V39, a tank destroyer built by ARL in 1939, is clearly based on the ARL 37 and is a good clue to how the ARL 37 may have looked like.

Yet the ARL V39 was 25 tonnes lighter, had only 50 mm of armor, and used 190/240 hp engines, completely different from the heavy tank. The ARL designs, and the FCM and AMX proposals all “used” non-existent engines. The FCM and AMX designs weighed over 50 tonnes and required two V12 engines of unknown power.

The ARL V39 self-propelled gun prototype. Despite being a good 25 tonnes lighter than the AMX 37, it was inspired from the designs of the AMX 37 and would be a good indicator of how the ARL 37 looked like.
Source: Pinterest

Conclusion

Each variant of the ARL proposal tried to fix larger, underlying issues. Variant C was the “standard” French design, akin to the Char B1 Bis. However, the overworked commander and gunner/driver would have been a huge drawback, as proven on the B1. Variant S tried to fix this, by having a larger, three-man turret. Yet the larger turret proved to be very wide and it did not fix the overworked driver issue. Variant V eased out the work for the driver, however, now the commander had to aim two guns, and still relied on the driver to traverse the tank when aiming the 75 mm howitzer. All in all, it proved that multi-gunned tanks were not a good idea.

Just like the other competitor’s designs, the ARL variants failed. The entire project was deemed too expensive and the tanks could only be produced in small numbers. Logistical and reliability issues might have appeared when building such a large vehicle with engines made from scrap. The weight and size of the ARL variants are unknown, however, they most certainly went over the 45 tonnes mark. A final blow came when the Conseil Supérieur de la Guerre (Eng: Superior War Council) decided on 26th March, 1937 that a much smaller, cheaper yet heavily armored tank would be designed instead. This in turn went south as well, when the Section de l’Armement et des Études Techniques (Eng: Section for Technical and Armaments Studies) made a study which showed that a tank fulfilling those criterias was already under development, and there would not be a need of a new program. This tank was the Char G1.

The ARL 37 would continue to influence the ARL V39 Self-propelled assault gun, and in February of 1938. the requirements of a heavy breakthrough tank changed. Most importantly, the weight restriction was removed. This led to the development of the ARL 39 and ARL Tracteur C super heavy tanks.

ARL 37 Variant C. Note that the appearance of hull is mostly speculative.
ARL 37 Variant S. The significant difference between the SA35 and Model 1934 gun is clear. Observe the cupola with 7.5 mm MGs.
ARL 37 Variant V. The odd dome shaped casemate and the small unmanned turret are what made Variant V such an unusual design.

Sources:

Chars-francais.net
DGA Châtellerault
TNT number 11
Chars De France, Jean-Gabriel Jeudy
Memoiredeshommes.sga.defense.gouv.fr
Wikimaginot.eu
Modernfirearms.net

ARL 37 specifications

Variants C S V
Dimensions (L-H) 7.52 x 2.86 meters 7.52 x Unknown 7.52 x 3.12 meters
Total Weight, Battle Ready 45+ tonnes*

 

Crew 4 5 6
Propulsion Unknown; its competitors used 2x V12 engines
Speed 30 km/h*
Range 200 km*
Suspension Leaf Spring
Armament 1x 75mm model 1929 (11+ rounds)

1x 47mm CA-35 (106 rounds, 98 in hull and 8 in turret.

1x 7.5mm MAC

1x 75mm model 1929 (11+ rounds)

1x 47mm Mle 1934

2x 7.5mm MAC

1x 75mm model 1929 (136 rounds)

1x 47mm CA-35 (114 rounds)

3x 7.5mm MAC (5400 rounds)

Armor 100 mm (4 inch) all around
Total Production 0; partial blueprints only

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