Categories
WW2 French Superheavy Tanks

AMX Tracteur B

ww2 French Tanks France (1939-1940)
Heavy Tank – None Built

During the interwar era and particularly the 1930s, French design bureaus designed a large number of heavy tank designs, with the main incentive behind these projects being creating a tank able to perform offensive operations against enemy fortifications. The Char de Bataille program, which had resulted into the B1 and B1 Bis, had at least partially been thought of with an anti-fortification role. While the B1 appeared a capable design, the study of heavier and larger designs continued – with the 45-tonne program leading to projects by AMX, FCM and ARL, and later, some even larger projects such as the ARL Tracteur C & Char de Forteresse FCM F1 being proposed.

In this context, one of the later anti-fortification tank proposals, which was submitted without going into the super-heavy gigantism of vehicles like the FCM F1 or ARL Char de Forteresse, was the AMX Tracteur B. It was presented in September of 1939 and further refined in January of 1940. It appeared as a fairly modest and classic heavy tank that would be in the 35-40 ton range. The project was studied by Joseph Molinié, the head of AMX’s armored vehicles design bureau.

Two general views of the AMX Tracteur B, part of the first documents of the design, dated November 1939. Source: Mémoire des hommes

The Tracteur A: AMX’s heavy self-propelled artillery

The Tracteur B tank proposal did not appear in a vacuum. Instead, the tank was based on a previous chassis AMX had been working on for a vastly different purpose, the Tracteur A. Rather than a single vehicle, the Tracteur A was a family of four different tractors, 45 to 55 tonnes in weight – AA, AB, AC, and AD – which would, when combined together, provide for a self-propelled 370 mm artillery piece (carried on tracteur AD). The Tracteur A family, which had been in study since 1937, were tracked motorized chassis with a suspension, and, as such, were thought of as a potential basis to create a tank.

One of the Tracteur As, the AD, which mounted the 370 mm barrel. Source: armedconflicts.com

The Tracteur A project appears to have originated around 1937. By 1940, six tracked chassis appeared to have been ordered to AMX to serve as prototypes, showing the project was well underway. As for the study of a tank based on the Tracteur A, the first mention of the Tracteur B dates from September 1939

The AMX Tracteur B’s general design

AMX’s Tracteur B project is known through a series of eleven plans, dated from November of 1939 to April of 1940. These mostly concentrate on the vehicle’s suspension and turret design, leaving notably the hull and its internal arrangement less clear.

The Tracteur B could be shortly described as a vehicle designed with the same dual configuration as the B1/B1 Bis, but with heavier weapons. In terms of size, the vehicle would be slightly larger than the B1 Bis in all dimensions. The weight the vehicle would have had is unknown, with estimations ranging all the way from 35 to 42 tonnes.

Hull design

Cutaway view of the AMX Tracteur B from the front/rear, showing the hull extensions covering the coil springs and the position of the tracks. Source: Mémoire des hommes
Top view of the AMX Tracteur B hull, showing its simple general shape. Source: Mémoire des Hommes

The hull design the AMX Tracteur B sported appears surprisingly simple overall. The vehicle would nonetheless have some features which would seemingly complicate its design, notably a hull-mounted gun. Whatever views are available of the AMX Tracteur B show a simple hull design. The front glacis would be fairly significantly angled backward, while the side plates would be mostly flat. This would be somewhat troubled by the suspension, with the springs being contained within two side extensions of the hull which would make the hull itself wider towards the bottom than the top. With the tracks, the vehicle’s width would be the same everywhere. The AMX Tracteur B hull was noted to be 6.73 m long in the first set of plans dated November of 1939. However, this set of suspensions specifies that this may be subjected to lengthening. The vehicle was indeed lengthened, with a new set of plans from January of 1940 placing the vehicle’s length at 6.948 m from the front to the end of the suspension; the uncertainty around the length to begin with likely related to uncertainties around the engine compartment and trench crossing capacities. An undated plan focusing on the suspension placed its length at 7.023 m, which may have been the length of the project as of June 1940. The hull would have been 1.915 m high, and 3 m wide exactly, with the tracks being 50 cm wide on each side. The Tracteur B’s hull would likely have housed three crewmen: a driver, a loader, and a radio operator.

The glacis would have been given a fairly thick 80 mm of armor, and well sloped. The rest of the hull would be armored to 70 mm, or 40 mm angled to be equivalent to 70 mm in some parts of the hull extending to cover the suspension. The floor appears to have been as thick as 35 mm, giving a fairly decent protection against mines, and the roof 30 mm thick. The hull appears to have used welded construction, with the exception of the front hull, which would have been a cast piece. With a minimum of 70 mm effective armor all-round the design would effectively be immune to the primary German anti-tank gun of the day, the 37 mm Pak 36.

Hull armament

As mentioned previously, the AMX Tracteur B would have had a dual armament configuration, as on the B1 and B1 Bis, with a turret-mounted anti-tank gun and a hull-mounted infantry support gun.

Three different hull guns appear to have been proposed to be used on the AMX Tracteur B. It does not appear any of these three guns had been chosen as the final one by the point work on the project stopped in June of 1940.

The 75 mm gun mount of the B1 n°101-based B1 Ter prototype/mockup. A less massive mount would likely have been featured on the AMX Tracteur B. Source: Tank Archives.

The first gun would have been the same 75 mm SA 35 as on the B1 Bis and B1 Ter – in this case, likely in a mount similar to the latter, which would allow for some form of lateral traverse of the gun without the need to traverse the hull for every fine adjustment. This gun fired shortened versions of the shells fired by the classic 75 mm mle 1897.

Two were available, the first being the Obus de rupture Mle.1910M (English: Rupture Shell model 1910M), which was an armored piercing high-explosive shell. The shell had a weight of 6.4 kg and contained 90 grams of explosives. It was fired at a muzzle velocity of 220 m/s. It offered an armor penetration of 40 mm at an angle of incidence of 30° at 400 meters, though it was mostly meant to be used against fortifications. The other shell was the Obus explosif Mle. 1915 (English: Explosive Shell model 1915), a high-explosive shell. It weighed 5.55 kg and contained 740 grams of explosive. It was fired at a muzzle velocity of 220 m/s.

The armored vehicle mount of the APX 75 mm gun, found on the SaU40 and ARL V39 prototypes, and in a variety of paper projects. Source: Wargaming

Another 75 mm option was considered, the 75 mm APX mle. 1929. The same gun as used on the SaU40, and perhaps considered for the FCM F4. This was a somewhat higher velocity gun. It fired the same ammunition as the old 75 mm mle. 1897, meaning, roughly speaking, lengthened versions of the same shells as the 75 mm SA 35, with the addition of a variety of shells which were never adopted in a shorter version such as, for example, canister ammunition. It had a muzzle velocity of 574 m/s and a rate of fire of about 15 rounds per minute on average in fortifications (though likely far lower within the constraints of an armored vehicle with a limited crew). This was already a more powerful option than the 75 mm SA 35.

A 105 mm model 1919 mountain gun in Ciudadela de Jara (English: Jara Citadel), Spain. The type was license-produced by Spain during the interwar year, with this example produced in 1931. Source: http://almadeherrero.blogspot.com/

A third option was considered and would have provided the AMX Tracteur B with even more firepower against fortifications and infantry, a 105 mm gun. This would likely be a derivative of the 105 mm Schneider mle. 1919/1928, which was a short howitzer meant for mountain operations. This resulted in a short gun with a barrel length of only 98 cm (11 calibers). Its high-explosive shells had a weight of 12 kg. The explosive charge is unknown but would have been of several kilos, significantly more than 75 mm shells. In standard operations, five different charges would be used for the high-explosive shells, which would have resulted in a muzzle velocity varying from 184 to 350 m/s. To simplify operations within the constraints of an armored vehicle, a single standardized charge would likely be used there. In operations, the 105 mm short gun would manage 3 to 5 rounds per minute during a short barrage of 3 minutes, and otherwise one round per minute of sustained fire, mostly due to the gun’s light construction and carriage. The rate of fire would likely be somewhat similar within an armored vehicle, though, with a specialized tank gun mount instead of a light mountain carriage, short sustained barrages at higher rate of fires may be possible with a sufficiently trained and rested loader. It appears this 105 mm option was preferred by the lead engineer, Molinié.

The gun, whatever model may have been chosen, would have been mounted right of the center of the vehicle, at around mid-height. While there are little details on the mount, it was reported to be planned to have at least some degree of lateral traverse. In terms of operations, the same configuration as on the B1 series, with the driver also assuming the role of gunner while another crewman operated as loader, would likely have been retained.

Interestingly, a source also reports that the AMX Tracteur B would have featured three MAC 31 hull machine-guns. One would be installed on the hull front, and two would be present on the sides; these would be mounted through gaps in the suspension, between the first and second return rollers from the front. These do not appear to have been represented on any available plans of the AMX Tracteur B though.

Suspension and drivetrain

The AMX Tracteur B would have had a suspension system fairly similar to the Suspension AMX found on the Renault R40, with AMX generally using a similar style of suspension in this era (with some notable exceptions, such as the AMX-40). In the case of the Tracteur B, the suspension was already in existence before the rest of the design due to the project being an offshoot of the Tracteur A.

A view of the Tracteur B’s suspension arrangement (showing the loading weight on the different bogies), showing the three bogies and the four road wheels outside of them. Two were linked to a single spring without a boogie and two independent wheels to the front and rear.
A view of the suspension without the coil springs, showing the arms for the front and rear road wheels. Source: Mémoire des hommes

The AMX Tracteur B’s suspension featured sixteen small (29 cm diameter) doubled road wheels. This meant there would be one wheel on the outer and one on the inner side of each track. The forward and rear road wheels were independent. The remaining fourteen were divided as follows: the twelve front wheels were distributed between three bogies, each linked to two coil springs linked to two road wheels. The rear two were linked to a coil spring without a boogie. The tank was designed with a large rear sprocket wheel (83.2 cm diameter) and front tender wheel (80 cm diameter). Five return rollers were present on top of the suspension to maintain tension.

The bogies and springs would be contained within the armored hull of the vehicle, which extended outward to contain the suspension. This meant they would be protected by 70 mm of armor, giving the vehicle an overall well-protected suspension. The tracks found on the AMX Tracteur B appear to have been of fairly similar design to those of the B1 Bis. Not only did they feature the same width, but the Tracteur B’s also appear to be large welded links. They may even be the exact same as on the B1 Bis. This suspension system and tracks were obviously geared towards optimizing cross-country performances at the expense of maximum speed on road. This shows the AMX Tracteur B was, like the B1 Bis or the various 45 tonnes and Char de Forteresse projects, designed to assault enemy positions and fortifications across rough terrain, potentially battered by artillery and marked by the presence of trenches, ditches, and other irregularities.

A front view of the Tracteur B’s suspension with cut-open springs, showing the doubled road wheels and large cast plates riveted onto shoes links used by the design, largely similar to those found on the B1 and B1 Bis Source: mémoire des hommes

The power plant which would have been used to move this suspension around is unknown. Whatever little views we have of the vehicle do hint towards a rather large engine compartment, but which engines would have been placed there is unknown.

Turret

Pretty interestingly, while a fair number of French 1930s designs used off-the-shelf turrets shared by different vehicles or projects, the AMX Tracteur B appears to have had a turret designed purposefully for the vehicle, though it does show some similarities with the classic APX cast turrets. Curiously enough, this turret was offset to the right, meaning it would have been on top of the 75 mm gun. The turret ring appears to have been 1.285 m wide. With the turret, the tank would stand at 2.965 m high.

A top view of the Tracteur B’s turret, showing its non-symmetrical design due to the armament being mounted to the right; the commander would therefore sit left. Source: Mémoire des hommes

The Tracteur B’s turret used a hexagonal asymmetrical design, with the front left plate being significantly larger than the front right, due to the armament being shifted to the right. As the vast majority of French turrets of the time, it would have featured an openable rear hatch/door, though it appears the choice was still to be made between a two and one-part hatch. Offset to the left was a commander cupola, fairly similar to the one on the B1 Bis’s APX 4 in design, and would be rotated by hand in order to bring its front episcope to whichever location the commander would want to observe.

A front view of the turret, showing the offset main armament but also the side episcopes, turret ring, and internal space. Source: Mémoire des Hommes

In terms of vision, the turret featured a number of episcopes. One was in the cupola’s front. One was featured in each of the turret side plates. An unknown vision device, likely some sort of vision port, was present on the front left plate. A coverable vision slot would also be part of the rear door.

The turret used cast construction. To the front, the turret would be 80 mm thick, while the rear-side plates and likely the rear plate as well were 70 mm. However, while all of the turret’s armored plates were angled inward, those towards the rear did so at a higher angle, and protection would overall be similar from all angles. As often with French 1930s projects, this turret contained only one man, the commander.

Three cutaway of various points of the turret; these match the first schematic found in this category, with AB being the rear-left plate, CD the front right and EF the front left. Source: Mémoire des hommes

Turret armament: A powerful anti-tank gun

The main armament of the Tracteur B was a powerful 47 mm anti-tank gun. This was a model of the 47 mm modèle 1934 Région Fortifiée (English: Fortified Area 47 mm pattern 1934, an anti-tank gun which had been designed for use in Maginot line fortifications), one of the most powerful dedicated anti-tank gun of the 1930s.

A 47 mm model 1934 during trials. In normal operation, the gun would be placed on a beam on the ceiling of the bunker, and could be exchanged with a machine-gun mount. Source: http://www.lignemaginot.com/

The 47 mm mle. 1934 was an L/50 gun that fired an armor-piercing capped shell that featured a magnesium cap. This was a quite heavy 47 mm shell, weighing in at 1.670 kg and propelled by a 610-gram charge of powder, giving it a muzzle velocity of 880 m/s. At an incidence of 30°, it would penetrate 77 mm at 500 m and 56 mm at one kilometer, more than adequate to deal with the majority of tanks from any nation of the era.

Within fortifications, the gun could be expected to fire at up to 15 to 20 rounds per minute, however, this would be way lower within the constraints of an armored vehicle. Within the B1 Bis, the rate of fire of the 47 mm gun would typically be around two rounds per minute, and its shells were lighter than the Tracteur B’s.

The gun featured two hydraulic brakes for recoil, which were protected by an armored cover sticking out from the mantlet. Elevation and depression were to be +15 to -10°. The 47 mm gun was combined with a coaxial 7.5 mm MAC 31E machine gun, with elevation tied to the main gun. This was the standard tank machine gun of the French army, firing the French 7.5 x 54 mm cartridge at a rate of fire of 750 rounds per minute and a muzzle velocity of 775 m/s from 150-round drum magazines.

A cutaway view of the turret showing the large breech, armored recoil recuperator, position of the rear hatch, and commander looking through the cupola episcopes. Source: Mémoire des hommes

The design does not appear to have been mature enough to have recorded the amount of ammunition stored inside the vehicle for either the main gun or the machine gun. It ought to be noted the 47 mm’s breech was very large and would have left the commander cramped, and internal space for other components was fairly lacking.

Conclusion – A project interrupted by the German invasion of France

As with the vast majority of ongoing projects in 1940 France, work on the AMX Tracteur B would be interrupted by the German invasion of France. While some covert work would continue on the base of some of the designs which were at prototype stage or further, such as the S40 or B1 Ter, pretty much no attention was given to what was little more than a set of schematics in Vichy France.

In terms of capacities, whatever we have of the Tracteur B would suggest it would have been an improvement of the B1 Bis in terms of anti-fortifications and anti-tank capacities, thanks to its more powerful anti-tank gun and hull gun had the 75 mm APX or 105 mm been retained. Its armor protection would also have been slightly thicker. However, while, in a vacuum, the tank would be superior to the B1 (supposing that the large engine compartment would allow for a powerplant powerful enough to give it at least equal mobility), what was little more than schematics by the spring of 1940 would likely only have been able to enter service in 1942 or later; AMX itself claimed that was the project adopted, a mild steel prototype would be completed by July of 1941. By that point, its 80 mm of armor protection (at an unknown angle, that being said) would already start to be less impressive, as well as its 47 mm anti-tank armament. Most significantly, the type retained the one-man turret which would have largely diminished the quality of the anti-tank gun’s operation, as well as outside observation for the commander. Even the hull gun would have retained only two crewmen to operate it, one also having to drive the tank around, giving it sub-optimal operations – particularly if the 105 mm, and its large and heavy shells, had been chosen. As a whole, the AMX Tracteur B shows that dual gun tanks, with a large gun in the hull and smaller gun in the turret, would overall not have remained a truly viable solution late in the war – even more so in French vehicles, which, unlike for example the American M3 Lee, retained small crews which hampered the operations of the tank’s armaments.

The later lengthened general view of the vehicle, dated from January of 1940. The Tracteur B is one of many French dual gun heavy tanks which never went beyond the drawing board. Source: Mémoire des hommes
Illustration of the AMX Tracteur B, created by Pavel “Carpaticus” Alexe and funded by our Patreon campaign

 

AMX Tracteur B specifications

Dimensions (L-H-W) 6.948 m / 3.000 m / 2.965 m
Weight in battle order 40 tonnes (empty) / 42.6 tonnes (in combat order)
Suspension Coil spring (rear drive sprocket & transmission)
Road wheels 16
Track width 50cm
Crew 4 (Commander/gunner/loader, driver/gunner, loader, radio)
Main armament One hull gun (either 75 mm ABS SA 35, 75 mm APX model 1929, 105 mm gun based on the Schenider model 1928 mountain gun)
47 mm modèle 1934 R.F (turret)
Secondary armament MAC 31E 7.5 mm machine gun
Hull Armor 80 mm (front)
70 mm (sides)
40 mm (part of hull extensions)
35 mm (floor)
30 mm (roof)
Turret armor 80 mm (front plates)
70 mm (rear plates)
Likely 30 mm (roof)

Sources:

GBM n°111, January-February-March 2015, “Les derniers Chars B”, Stéphane Ferrard, pp 83-96, Histoire & Collections editions
Plans of the AMX Tracteur B via Mémoire des hommes
Char-français
Notice provisoire sur les matériels de 47 et de 37 de casemate mle 1934 du 4 mars 1939 via Wikimaginot
Wikimaginot
lignemaginot.com
http://almadeherrero.blogspot.com/2019/11/obus-de-105-cm-modelo-1919-en-la.html
Trackstory n°13: Le Char B1, Editions du Barbotin, Pascal Danjou

Categories
WW2 French Superheavy Tanks

Char de Forteresse ARL

ww2 French Tanks France (1939)
Superheavy Tank – Blueprint Only

In 1937, the French military requested the design of heavy breakthrough tanks to be able to take on the German Westwall Line being built alongside the French border, vis-à-vis the Maginot Line. This was the Char Lourd (Eng: Heavy tank) program. Three companies presented designs, ARL, AMX and FCM, but the program was halted, as the tanks would have been too expensive, and too few could have been built to have any significant impact on the battlefield.

So, naturally, the weight limits were lifted, allowing the companies to create even heavier and more expensive designs.

History

The authorities were most impressed by the design of the FCM F4, granting, in February 1938, some changes in the requirements: A 75 mm gun in the turret and no weight limits. As a result, the French Supreme Command granted FCM, on 6th April 1938, a contract for the development of such a super-heavy tank; the Char F.

Simultaneously, a commission headed by Julien François René Martin reanalyzed the threat presented by the Westwall, urging the revival of the Char Lourd program. These new versions would be differentiated by being called Char d’Attaque des Fortifications (Eng: Fortification Assault tank). The new design should have had a gun in the turret, suitable for close-range fire, and be immune to the best anti-tank guns in Germany at the time. Hence, speed was not of importance, with a 10 km/h top speed seen as satisfactory. In addition, it was to have outstanding trench, ditch, and river crossing capabilities, leading to a very long vehicle. In April 1938, the High Command approved the plans and dispatched another commission, with the task of fine-tuning the requirements and figuring out if the 45 tonne Char Lourd program could have been revived instead of making new, heavier designs.

Second Commission’s first meeting

On 4th May 1938, the Direction des Fabrications d’Armement (Eng: Armament Production Department) wanted to call this new program the Char H, but it was rejected, so as to not bring confusion with the Hotchkiss H35 tank. Five days later, the second commission, at its first meeting, wanted to make two types of tank, a 45-tonne tank and a superheavy tank. French author Pierre Touzin states in his book, ‘Les véhicules blindés français, 1900-1944’, that the commission wanted the tanks to be immune to at least 47 mm guns, so they agreed on 120 mm armor thickness. They would also give the option of 75 or 47 mm guns (or a combination of both) in a turret or more. The 75 mm would only be required to have a muzzle velocity of 640 m/s. The secondary armament had to include a flamethrower. However, the Commission did acknowledge the dangers and space taken by the flammable fluid, but they also had suspicions about the effectiveness of mounting such a weapon. Thus, they proposed either:

  • A towed trailer carrying the liquid fuel
  • A very bulky and heavy tank

Nonetheless, the problems of transporting such a vehicle by rail were solved by simply deciding to avoid rails and to carry it on roads.

45 tonne/articulated option

The first solutions came regarding the 45-tonne vehicles. It was to be armed with a cannon, a flamethrower, and machine guns. It was to be able to reach a top speed of 10 km/h. A prototype study was made, of slightly smaller dimensions, similar to that of the Char G1, with 100 mm of armor and a gun inside a casemate.

Mockup of one of the Char G1 from Renault. Despite sharing nothing in common to the Char de Forteresse program, the first prototype study was around the same size as the G1.
Source: Globalsecurity.org

The Commission did confirm that the 45 tonne Char Lourd program was not enough, as it was impossible to have 120 mm of armor, a 75 mm gun, and good trench crossing capabilities under 45 tonnes. After all, all Char Lourd designs exceeded that mark and had even thinner armor (100 mm). Therefore, to be able to fulfill the requirements, the creation of an articulated, modular design was brought up. It would be brought on roads via trucks and be reassembled before reaching the frontline.

Installment of a flamethrower could not be done either, as it would have required a special towed trailer, also with 120 mm thick armor. It was calculated that the fuel volume required was 6 m3 for just 4 minutes of firing. The concluding idea was that there should be a gun tank and a flamethrower tank, built jointly, in two parts.

Superheavy option

The second idea was the creation of a super-heavy tank. It was to also have a modular construction, but only with the weapons, main cannon, flamethrower, and machine guns, which could be demounted for easier transport. This was all the idea of the Infantry Directorate, which itself resumed General Estienne’s previous plans. However, the main problems with this variant were that:

  • The assembly would require a lot of resources
  • The turret would be overcrowded by the main gun and flamethrower

They did acknowledge that a tank with crossing abilities similar to that of the Char 2C (4.5 meters) and a fording depth of 1.4 meters but also with 120 mm armor would have weighed between 150 and 200 tonnes, a benchmark where even a modular vehicle would not be effective.

LEGO tank option

A third idea was brought up at the meeting. To be able to enjoy the advantages of a super-heavy tank but to also have the same transportability as a heavy tank, they came up with a 60 to 65-tonne tank that would be made entirely out of portable modules: turrets, ammunition, fuel, engine, etcetera. This would leave an empty hull of around 45 tonnes, which could be transported by trucks. Of course, the main downside was that the tanks had to be reassembled bit by bit before being combat-ready.

Second meeting

On 22nd July 1938, the new commission had its second meeting. Tests were made to see if 100 mm was in fact, sufficient protection. It was deemed enough to withstand fire from existing 75 mm guns then in service, but would not be enough for newer 75 mm guns firing AP, thus the 120 mm armor was necessary. The existence of the German 8.8 cm Flak gun was also seen as a reason to keep the original 120 mm threshold.

The results of the experiments surrounding the flamethrower and its dilemmas were to come in by the end of the summer.

Further rework on the designs allowed for ditch crossings of 6.5 to 7 meters. It was also remarked that trucks could only carry a weight of 35 tonnes, with an 8 axle transport trailer. However, railway wagons could transport a weight of 100 tonnes and special axles could be built if necessary, reviving the option for rail transport.

Several design options were evaluated at this meeting as well.

Char Minimum: armored with 120 mm thick armor, a 75 mm gun in a turret, and two flamethrowers (probably in the hull). The cannon version weighed 56 tonnes and could be reduced to 40 tonnes for transport. The flamethrower variant was a bit heavier, at 57 tonnes, plus a towed trailer. The Char Minimum’s poor trench crossing distance of “just” 2.5 meters lead to it being rejected.

Char Maximum: Classical layout tank with 120 mm armor, 75 mm gun in a turret, and just one flamethrower. It could cross 3.6-meter trenches (still less than the Char 2C). Although it weighed around 89 tonnes, it could be demounted into two main pieces for transport.

Train Boirault: French engineer Monsieur Louis Boirault was, and still is, known for his unorthodox solutions regarding tank design, especially trench crossing. As early as 1915, he presented articulated tank trains that would, theoretically, improve cross country capabilities. This 1938 variant had three self-coupling main parts and weighed 125 tonnes in total (41.6 tonnes each). However, its turning radius was large and the couplings unreliable and hazardous. Reducing the train to just two modules fixed some issues but created others, and was ultimately rejected.

One of Boirault’s later inventions. This one uses several S35 like tanks plus a middle section.
The 1938 125 tonne version might have been something similar, just larger.
Source: French Patent FR818469

Char Squelette: Inspired by the WWI ideas of the Skeleton tank and Boirault Machine, this variant greatly interested the Commission, both out of curiosity and also actual implementation. It had a small armored ‘box’ that was attached to rotatable beams, shifting the vehicles’ center of gravity, thus allowing it to cross 8 meter long trenches. Unsatisfactorily, the turret was unable to rotate a full 360° and many of the automotive elements and beams were exposed to potential enemy fire. The total weight was 110 tonnes.

The American Skeleton tank. The French version would have been rather similar, but much larger.
Source: Landships.info

The commission approved the Char Maximum and Char Squelette and insisted upon the 120 mm armor, 75 mm gun in the turret, and one flamethrower.

In September, the Supreme Command asked for the immediate design of a Char Maximum and a replacement solution for the Char Squelette.

L’Atelier de Construction Rueil (ARL), located on the outskirts of Paris, was tasked with the development and creation of blueprints. They had previous experience with heavy tanks, as they had presented three designs a year earlier for the Char Lour program. FCM, Somua and AMX, the other main French tank factories, were all busy with other programs. Besides the aforementioned characteristics of the Char Maximum, they were to also protect the bogies and wheels with side skirts, and the tank had to be demountable into 45-tonne sections.

In the summer of 1939, ARL presented the drawings of two different alternatives: an articulated and a classical long variant. Besides the layouts, they were more or less identical. They called it Char de Forteresse (literally Fortress tank).

Two drawings

The articulated variant had two 60 tonne modules, for a total weight of 120 tonnes. One was the fighting compartment, with the weapons and crew, and the other was the engine and fuel compartment. Each module had its own driven sprocket, indicating that the coupling between the two was more complex, as power would also have to be transferred between the two. It is unspecified if the vehicle turned by pivoting the modules, like a BV206, or by breaking the tracks. Considering this was never specified, it is unlikely to have included such a steering system, as it also added additional mechanical complications. The Commission noted that there were not any visible problems with the design, however, they did express a desire for a second gun in the “rear”. It is unclear if this would have been on the rear of the armament module or the engine module. They also wanted to test and check the effectiveness of the 75 mm gun against reinforced concrete armor, the type used in the bunkers on the Westwall. The flamethrower(s?) was to also be removed since it was seen as useless against fortifications. ARL added twin engines to the designs, but the Commission only wanted one. This would free up space for ammunition, better communication between the compartments, close-range defense, and providing the crew with sufficient space.

Plans of the articulated variant. Note the lack of design on the articulation, showing just how little the design had come.
Source: Chars Français

The other drawing was a much more classical layout for a tank of this type, with a very long hull, the engine in the rear, and the turret at the front. The turret used on both designs was somewhat hexagonal in shape, with a large extension behind the gun in order to provide a better view for the commander. It is possible that it might have mounted a rangefinder as well. The running gear was long, protected by heavy side skirts. Large idlers and sprockets ensured improved ditch and trench crossing.

The second design proposed by ARL. It was extremely long, around 12 meters, for excellent trench and ditch crossing.
Source: Chars Français

Layout and components

Very few technical details are available, and it is quite likely the designs never even got that far. The main armament was an unspecified 75 mm gun, but considering previous designs, it was most likely a 75 mm Mle. 1929. It also received additional armor around the gun, characterized by the mushroom-like object on the barrel. The hull length was around 12.05 meters, the width of around 3.20 meters, and the hull height of 2.125 meters. The total height would have been 3.65 meters.

The engine and powertrain are hard to determine. Later vehicles, such as the FCM F1 and ARL Tracteur C, used two Renault 550 hp engines, but since only one engine was desired, it is hard to say what contemporary French engines could propel this 120-tonne beast. On the other hand, a 10 km/h top speed was deemed sufficient, although some sources claim it would have reached 18 km/h. This engine would have probably been attached to an electrical generator that powered the drive sprockets. The crew number and positions are also a mystery. The most likely number would be around 5 crewmen, a commander, gunner, loader, driver, and radio operator or mechanic (the radio might have been handled by the commander).

The armor was 120 mm thick almost all around. It was common for French tanks to have the same thickness all around, with small exceptions, like the top and belly armor. This shows how the tank could easily reach the 120-tonne mark, despite the small turret and even smaller armament.

Armament

The main armament was most likely an APX 75 mm Mle. 1929. This gun was originally developed for the Maginot Line and was an improvement of the gun mounted on the Char B1. ARL had previously used it on their ARL 37 heavy tank and ARL V.39 tank destroyer. The Mle. 1929 normally had an armored sleeve, but ARL gave it a ‘head’ to deflect incoming rounds.

It is unclear which flamethrowers would have been used, and they were eventually to be removed from the tank, as they were deemed unnecessary.

The 3 machine guns would most likely have been MAC-31s. Also built for the Maginot Line, these heavy machine guns fired 7.5 mm cartridges from 150-round magazines, ideal for use in tight spaces like tanks. One was in the gun mantlet, one in the hull, near the driver and one mounted on the rear, for defense against flanking infantry.

MAC-31 machine gun with a drum magazine
Source: Wikipedia

Turret

The turret was a Tourelle ARL 4 with a hexagonal shape, made out of welded 120 mm thick plates. This was rather unusual, as most French turrets were cast. The commander had a large protrusion, providing an excellent view over the battlefield. He sat on the left side of the gun and had around 7 cutouts or slits for vision, a rather archaic solution, instead of using periscopes. It was hinged on the front side of the turret, allowing the commander to enter and exit, while also providing protection. The turret was large enough to fit 3 men, the commander, gunner, who sat below and in front of him, on the left side of the gun, and the loader, who was also responsible for the coaxial (or possibly independent) machine gun in the mantlet.

German threat and merging with FCM program

Since the final design by ARL was very similar to the one FCM was working on, the Char F, the Commission decided to end the development of the Char de Forteresse in order to allow both FCM and ARL to work on the same program and speed up the development of the Char Maximum. Things took a different turn in September of the same year, as Germany invaded Poland. The High Command was not too fond of the practicality and use of these super-heavy tanks, but the Commission proceeded regardless. In a meeting held in the same month, the Commission made changes to the FCM requirements, uparmoring it to 120 mm and requesting the mounting of a 105 mm gun in the hull. The Char Squelette was finally abandoned since it was too complex.

In October 1939, AMX would also join the program, and they would all work on different designs, getting heavier and with more and more guns. ARL cast aside their original plans of the Char de Forteresse, moving on towards other plans to keep up with the new demands. They did however use the general layout for further designs. Final outcomes were the mock-ups of the ARL Tracteur C or FCM F1, all of which were terminated prematurely due to the German invasion of France in the summer of 1940.

ARL Tracteur C uncompleted mock-up, with a German soldier posing next to it.
Source: Chars Francais

Conclusion

ARL’s Char de Forteresse was an insignificant and short-lived design, but, when put together with the previous Char Lourd program and future Char Maximum developments, it highlights the cluelessness of the French military, wasting valuable time and resources on trying to counter a mainly nonexistent defensive line. By the start of the Second World War, the Westwall was not more than just a series of ditches and dragon’s teeth.

Post Scriptum – Char de Forteresse 1940

The name Char de Forteresse does show up later on, unrelated to ARL plans. On 28th February 1940, a new commission, the Commission d’Études des Chars (Eng: Tank Study Commission), set off to create the structure for future tank development and production doctrine. Similarly to General Estienne’s interbelic doctrine, there were to be three tank types:

Char d’Accompagnement: a light infantry support tank, equipped with a 37 mm SA 38 gun, 40 mm armor, and a total weight between 10 and 12 tonnes. Later models would have the 47 mm SA 35, 60 mm of armor, and a weight between 15 to 20 tonnes. Top speed of 20 to 35 km/h. This was something similar to the Somua S35.

Char de Bataille: a battle tank armed with a 75 mm and 47 mm gun and 60 to 80 mm of armor. Similar to the Char B1 and B1 bis.

Char de Forteresse: a fortress tank armed with a 75 mm, 90 mm, 135, and/or 155 mm gun. Weight of 80 to 100 tonnes and a top speed of 20 km/h.

Clearly, the French did not learn much from either the FCM 2C or any of the other designs. This second Char de Forteresse was canceled not because they were utterly pointless and unusable, but because there were not any 135 and 155 mm guns suitable for the tank.

First Char de Forteresse ARL design, consisting of two articulated sections. Illustration by Pavel Alexe, funded through our Patreon Campaign.
Second Char de Forteresse ARL design, with a more traditional, ‘battleship’ hull. Illustration by Pavel Alexe, funded through our Patreon Campaign.

Sources:

https://www.chars-francais.net/2015/index.php/7-archives/de-1930-1940/2428-1939-char-forteresse-arl
Les Vehicules Blindes Francais 1900-1944 – Pierre Touzin, 1979
Chars De France – Jean-Gabriel Jeudy

Char de Forteresse ARL specifications

Dimensions (L-W-H) 12.05 x 3.20 x 3.65 m
Total Weight, Battle Ready 120 tonnes
Crew 5 men (Commander, gunner, loader, driver, radio operator or mechanic)
Propulsion unkown, included electrical generators
Speed 10 – 18 km/h
Armament 1x 75 mm APX Mle. 1929,
3x MAC 31 machine guns
2x/1x flamethrower (later removed)
Armor 120 mm all around
Categories
WW2 French Superheavy Tanks

ARL 37 ‘Char de Rupture’

ww2 French Tanks 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 (or Char de Fortresse) 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
Categories
WW2 French Superheavy Tanks

Tracteur FCM F4

ww2 French Tanks France (1937)
Heavy Tank – None Built

Back in the 1930s, the tank was still a relatively new weapon. The masterminds of the world’s most powerful tank forces were still debating about its role on the battlefield. Fits of paper fantasy showed engineers and designers putting on as much armor and as big of a gun onto a tank as their imagination could manage. The inventions’ power and potential seemed limitless to the minds of many, leading to the emergence of a type of heavy tank more akin to a land battleship. Most countries capable of building tanks were experimenting with their own models, from the British A1E1, Soviet T-35, to the German Neubaufahrzeug, to name the more “practical” designs.

During the same time period, the Germans were building the infamous Siegfried Line or ‘Westwall’, a fortified defensive line consisting of bunkers, tank traps, and much more arrayed along the western German frontier. Nothing in the French tank arsenal was able to challenge these potent defenses. Combining the multi-turret tank designs – in fashion at the time – and this new threat from the east, the French quickly realized they needed a new powerful breakthrough heavy tank able to withstand anti-tank fire and destroy static defenses.

Breakthrough Heavy Tank

With the doctrine of breaching the Siegfried Line in mind, a heavy tank program was requested by the Conseil Consultatif de l’Armement (Armaments Advisory Council) on 4th May 1936. The specifications for this new program, named “Char de Rupture 1937” (literally breakthrough tank), were released on 12th November 1936. The Conseil Consultatif de l’Armement requested:

“Char lourd, très protégé et très armé, propre en particulier à être utilisé défensivement et offensivement dans la guerre en région fortifiée”.

“A heavy tank, well armored and well armed, suitable for both defensive and offensive purposes in fortified battlefields.”

The tank was to have a maximum weight of 45 tonnes (49.6 short tons) and dual armament, with a main gun in the hull and a secondary gun in a rotating turret. The vehicle would need thick armor, capable of resisting incoming fire from anti-tank field guns at a distance of at least 200 m (220 yards). Requirements for the mobility and speed of the design were tight, with a top speed of 30 km/h (18 mph) and a range of 200 km (125 miles) or 10 hours.

A few months later, in 1937, three French companies presented designs, AMX, ARL, and FCM.

Forges et Chantiers de la Méditerranée

The Forges et Chantiers de la Méditerranée (Eng: Foundries and Shipyards of the Mediteranean), better known as just ‘FCM’, was a naval shipyard that specialized in heavy vehicles founded by the British engineer Philip Taylor in 1853. Besides building large warships, like the Paris battleship, they had produced tanks and armored vehicles before, such as the FCM 36 and Char 2C.

One of the FCM shipyards at Seyne-sur-Mer. Source: Wikimaginot.eu

In May 1937 , FCM presented their first design for this competition (FCM was last of the three to present a design), the FCM F4 Variant A. The company already had plenty of experience in building large heavy tanks, as 10 years earlier it had designed the FCM 2C, one of the largest tanks ever made. The company also proposed designs for the program that would eventually become the Char B1, in the form of the FCM 21.

Design

Variant A of the FCM proposal was based on their previous heavy tanks. It had a large, frusto-conical turret located on the front of a long hull, with large idlers and drive sprockets beneath. Its suspension was typical of French heavy tanks of the time. On each side, there were eight bogies with one leaf spring each. To each spring, two road wheels were mounted. In addition, on each end of the track, there were two road wheels connected to bump stops for driving over rough terrain, such as trenches. They did not touch the ground, however, they helped minimize the impact when the tank first came in contact with an obstacle.

The turret housed a 75 mm gun, while a 47 mm gun was mounted in the hull. This allowed for more effective usage of the 75 mm, as it could cover an area of 360° around the tank rather than being restricted by the limited traverse of a hull-mounted weapon. This, however, meant that a larger turret had to be made, pushing the height of the tank to over 3 meters. This turret was frusto-conical, typical of FCM turret designs of the era and had a rotating cupola with a rangefinder on top. The 75 mm gun had a designated gunner and loader in the turret, while the driver was in charge of aiming, shooting and loading the 47 mm. The commander was located in the center of the hull, so it might have been possible for him to assist the driver with loading the 47 mm gun, but this is uncertain as no plans of the crew layout exist. The overall weight would have been around 55 tonnes – far above the requirements.

Armament

While ARL and AMX went with a ‘traditional’ Char B1 layout of a 75 mm howitzer in the hull and a 47 mm gun in the turret, FCM went on its own path. Just like on the Char 2C, they mounted the required 75 mm gun in the turret. It is unclear what 75 mm gun this was supposed to be. Some sources claim it was the same as on the Char 2C, the Model 1897 75 mm howitzer, while others state the 75 mm Model 1929 would have been used. The APX 75 mm model 1929 howitzer was a modified version of the Model 1897 75 gun, with many components, such as the barrel, being the same. It was originally built for the Maginot Line as a static defense, but later modifications allowed it to be mounted on combat vehicles. The later tank destroyer projects ARL-V39 and Somua SAu 40 were also equipped with this gun. Likewise, the designs of FCM’s competitors, ARL and AMX, also mounted the newer howitzer in the hull.

The ammunition used is unknown, however, the same guns in the Maginot Line used HE model 1917 rounds with a muzzle velocity of 577 m/s. Ammunition stowage for all the weapons is unfortunately also unknown.

Tank gun mount of the 75mm mle 1929 howitzer, the same was used on the later Somua SAu 40 and ARL V39 tank destroyer projects. Source: Wargaming

As secondary armament, FCM used the 47 mm model 1934 gun, firing APX mle 1936 Obus de Rupture (Armour-Piercing High-Explosive, APHE) shells. Originally, just like the APX mle 1929, this gun was intended for the Maginot Line. These shells had a muzzle velocity of 880 m/s (2890 fps) 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 1000 m (1094 yards). The shell weighed 1.670 kg (mock warhead, translation from the French “fausse ogive”) and the charge weighed 610 g. This gun would have been aimed and loaded by the driver. This was common in French tanks and was done to reduce the number of crewmen needed per vehicle. However, naturally, this put the crew under a lot of strain and required more training. In addition, maintaining the tank with a smaller crew was more strenuous.

Version A was equipped with 2 machine guns (later versions would have up to 6) and these were the 7.5 mm MAC (Manufacture d’Armes de Châtellerault) model 1931. Originally built for use in static defences on the Maginot Line, it could also be mounted on tanks and other Armored Fighting Vehicles (AFVs). It was gas operated and fired the 7.5 mm MAS cartridge from a 150-round drum magazine. These rounds had a muzzle velocity of 830 m/s (2,700 ft/s). Its weight of nearly 12 kg (26,45 lb) meant that it had to be mounted on a heavy steel mount.


The 7.5 mm MAC 31 with a tank mount. The large 150-round side-mounted drum magazine meant that storage inside of vehicles (in this case tank) was simple and allowed for continuous fire, without the crew having to reload very often. This was crucial in French tanks as the crew already had a lot of tasks to fulfill. Source: Wikipedia

Engine

There is very little information on the mechanical parts of the FCM design. It is known that it was to be equipped with two V12 diesel engines. It is unclear what engine this would have been, but may be assumed this engine was being purpose-designed for this tank project and got canceled simultaneously. Each engine drove an electric generator that was connected to the final drive, similar to the later British TOG 1 and 2, and the German Elephant tank destroyer and Maus super-heavy tank. These engines were supposed to have allowed the 55 tonne tank to reach 30 km/h.

Armor

Like many other statistics about this vehicle, the armor thickness is mostly unknown. However, considering that the AMX design had 100 mm (3.94 in) at the front around the turret, it is relatively safe to assume that the FCM F4 would have had similar armor thickness. French tanks also tended to have the same armor thickness all around the turret. The frontal hull plate was well angled, and so was the turret, which increased its effectiveness.

Other Variants

After presenting the first version, FCM showed a second one, the FCM F4 Variant B. It was identical but had the transmission and exhaust moved centrally and an FCM 36 turret equipped with 2 machine guns was added, facing the rear. This increased the weight to 57 tonnes and the crew to 5. There are no images of this design.

In August 1937, FCM proposed 2 new designs. Version C had a new turret, also armed with a 75 mm gun. Version D had the 47 mm gun in the hull moved into the little turret in the back. In October, Version E was designed with 5 additional machine guns. Finally, in December, Version F was shown mounting a flamethrower and the total weight was pushed to 59 tonnes.

From Heavy to Super Heavy

All 3 companies – ARL, AMX and FCM – had their designs rejected because the tanks would have been too expensive and could only be produced in small numbers, therefore they would not have any large effect on the battlefield. To solve this, the Conseil Supérieur de la Guerre (Eng: Superior War Council) decided on 26th March 1937 to build a smaller and cheaper yet heavily armored tank. However, after testing, the Section de l’Armement et des Études Techniques (Eng: Section for technical and armaments studies) claimed that this would be redundant, as there was already such a tank under development – the Char G1.

The rear turret for Variant D. It was to be armed with a 47 mm SA 35 and a machine gun, in a smaller variant of the main turret.
Source: GBM 109

Due to this evolution, the requirements were changed in February 1938. There was to be no weight limit and a 75 mm gun had to be mounted in the turret. The same companies presented designs once again, however, these new specifications were very close to those of the original FCM design, so the Supreme Command gave FCM a contract to build the tank. This would eventually lead to the FCM F1, a 140 tonne monster with 2 massive turrets and a 90 mm gun. However, by the time a mockup was ready in 1940, France had been occupied by Germany and, consequently, all super-heavy tank designs were halted, meaning no French Char Lourd (heavy tank) would ever get the chance to batter the Siegfried Line.

FCM F4 Version A. The large turret and the rangefinder can be seen. Note the 4 holes in the sideskirts acting as mud shoots, to release mud from under the sideskirt.
Source: Pinterest

Tracteur FCM F4 Variante A
Tracteur FCM F4 Variant D

Specifications

Dimensions 7.5 x 2.94 meters
(24.6 x 9.65 ft)
Weight 55+ tonnes
(60.63 tons)
Crew 4 (commander, driver, loader, radio operator)
Propulsion 2 x V12 diesel engines connected to electrical generators
Maximum speed 30 km/h* (18 mph)
Suspension Leaf springs
Range 200 km* (125 miles)
Armament 75 mm model 1929
47 mm SA35
7.5 mm MAC

*These numbers are what was requested by the Conseil Consultatif de l’Armement . Actual numbers are unknown.

Sources

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


Categories
WW2 French Superheavy Tanks

AMX 37 ‘Char de Rupture’

ww2 French Tanks France (1937)
Heavy Tank – None Built

During the mid-1930s, Germany started construction of the Westwall, otherwise known as the Siegfried Line. This fortification spanned across the German border with France up until their border with Denmark and was equipped with numerous bunkers and cannons. The French authorities were alarmed by this and figured that they would have to overcome this defensive line. However, no tank in the French arsenal at the time was able to combat such an obstacle. Therefore, they quickly started a heavy breakthrough tank program, named ‘Char de Rupture 1937’.

Specifications

On the 4th of May, 1936, the Conseil Consultatif de l’Armement (Armaments Advisory Council) requested plans for a new heavy breakthrough tank that would be able to charge the Siegfried Line while being able to knock out static defenses and enemy tanks. A quote from the Council:

“Char lourd, très protégé et très armé, propre en particulier à être utilisé défensivement et offensivement dans la guerre en région fortifiée”.

“A heavy tank, well armored and well armed, suitable for both defensive and offensive purposes in fortified battlefields.”

The exact specifications were released on the 12th of November 1936. The tank was to have a maximum weight of 45 tonnes (49.6 short tons) and be equipped with two main armaments, a 75 mm gun and a 47 mm one. As it was supposed to lead the charge against bunkers and fortifications, it was to have thick armor, namely to withstand anti-tank fire from 200 m (220 yards). The mobility aspect was optimistic for a tank of the time, as it was supposed to reach 30 km/h (18 mph) while having a range of 200 km (125 miles) or 10 hours of operation.

By May 1937, 3 companies presented their designs, ARL, FCM, and AMX.

Construction d’Issy-les-Moulineaux

Construction d’Issy-les-Moulineaux (AMX) was created when the French government took over the Renault factories in 1936, ultimately meaning that the Char de Rupture AMX was one of their very first tank projects. AMX went on to design and build some of the most famous post-war French tanks, like the AMX-13, AMX-50 and AMX-30.

Production line of AMC-34 on the left and Renault D1 on the right, in the Ateliers de construction d’Issy-les-Moulineaux (Renault) before nationalization, 1935. Source: Wikipedia Commons

Design

In March of 1937, AMX presented its preliminary concept for the program. This was essentially an enlarged Char B1 Bis. Their design was elongated, with a 75 mm gun mounted in the hull to the right of the driver. On the roof, a small turret with a 47 mm gun and a machine gun were placed. There were two turret designs, the first one having the gun mounted on the right side and an unusual polygonal shape. The second turret was much more similar to that of the Char B1 bis and Somua S35, the APX-1, however, the armor on it had been increased considerably. As a matter of fact, the entire tank was covered in thick armor and, in typical French fashion, long side skirts were hiding the suspension, leaving only the massive tracks exposed. It had a crew of 4, driver, tank commander (located in the turret, manning the 47 mm gun) a loader and a radio operator. To reach the desired top speed, two V12 engines were to be used, each engine being coupled to an electrical transmission which, in turn, drove four electric engines, two per sprocket.

Artist’s impression of the AMX 37, most likely made to promote the design. Like many images of the kind, the proportions and details are off. The turret is of the late-type. Source: aviarmor.net

Original blueprints of the AMX 37. The resemblance to the Char B1 can be seen, with the large sprocket, side skirts and weapon placement. Note that the turret seen is the early type. Source: memoiredeshommes.sga.defense.gouv.fr
Front view of the tank. The mounting of the 75 mm model 1929 howitzer and the turret’s location can be seen. Source: memoiredeshommes.sga.defense.gouv.fr

Top view. Note the large, exposed tracks and odd polygonal turret shape. Source: memoiredeshommes.sga.defense.gouv.fr

Armaments

Just like in the Char B1, AMX mounted a 75 mm howitzer in the hull and a 47 mm gun in the turret. The 75 mm gun was the APX 75 mm model 1929 howitzer, a modified version of the famous Model 1897 75 mm gun, with many components, such as the barrel, being the same. It was originally built for the Maginot line as a static defense gun, but later modifications allowed it to be mounted on combat vehicles. The later tank destroyer projects ARL-V39 and Somua SAu 40 were also equipped with this gun. It was mounted to the right-hand side of the driver who was also the gunner. The main drawback was the poor gun traverse, only 6° to the left and right.

The APX 75 mm Mle 1929 on the mount designed for tanks and other AFVs. Source: Wargaming.net

The gun mounted in the turret was most likely the 47 mm SA35, the same gun used in the turret of the Char B1 Bis. It would have shot the same type of ammunition, the Obus de Rupture Mle 1935 (AP model 1935) weighing 1.620/1.625 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.

Side views of the SA35 from a B1 Bis. The mantlet mounted at the base of the barrel would be different on the AMX 37. Source: Warspot

The machine guns used on the tank were the 7.5 mm MAC (Manufacture d’Armes de Châtellerault) model 1931. Like many other French weapons of the time, it was developed to be mounted on the Maginot line, but was later adapted to be mounted on armored fighting vehicles and tanks. It was gas-operated and fired the 7.5 mm MAS cartridge from a 150-round drum magazine mounted on the left side of the gun. This large magazine meant that the crew did not have to reload as often compared to other machine guns (the German MG-34, when mounted on tanks and AFVs, had a 50 to 75 round magazine). Such a large magazine was crucial in the already overworked French tank crews, of which the AMX 37 certainly was not an exception. These machine guns were attached independently, next to the 75 mm and the 47 mm. Two more MAC machine guns were placed in ball mounts, next to the entrance doors on the sides of the tank, to better protect from infantry sneaking up on the tank. Due to the large suspension of the tank, the side machine guns had restricted traverse.

The 7.5 mm MAC Mle 1931 with a tank mount. The large 150-round magazine can be seen. Source: Wikipedia

Crew

Despite a large number of weapons, the tank only had a crew of four; driver, commander, loader and radio operator. In a similar fashion to the Char B1, the driver was also the gunner for the 75 mm howitzer. Since the gun only had 6° of traverse, the driver had to turn the entire tank to better aim the gun. The loader was loading the 75 mm and was located in the hull. He was also responsible for loading and firing the MAC machine guns to the right of the tank and the one coaxial to the 75 mm. Behind the driver was the turret and that was where the commander sat. He was responsible for searching for targets, firing and loading the 47 mm and, to top it all off, fire and load the co-axial MAC machine gun. The radio operator, located behind the commander, was in charge of the radio of unknown type, and the machine gun to the left of the tank. He could have also assisted the commander, giving him ammunition from the hull up and into the turret.

It was typical for French tanks to have one-man turrets, or to have overworked crews. The sheer amount of work that the commander had to do in the AMX 37, and many other French tanks of the time, was huge. He did not only have to command the tank and spot targets for the 75 mm gunner through his cupola, but he also had to aim, load and fire his 47 mm and, when necessary, the machine gun as well. This lead to an overworked soldier, having to complete so many tasks at once and doing neither very well. The reasoning behind this design was to decrease the amount of manpower needed to operate tanks. The fewer men you need per tank, the more tanks you can have. The shortage of men was deemed an issue in France during the 30s, as the population still had not recovered from the First World War. In practice, the French had overworked crews, and too few tanks, getting the worst out of both.

Top view of the crew compartment. The four crewmen’s position can be clearly seen with the driver, commander and radio operator sitting in a row with the loader on the far right. Note the two hull MGs overlooking the sides. Another interesting detail is the floor escape door most likely used by the driver or when another door was damaged, as the other three crewmen have their own doors. Separating the crew compartment and the engines is a pneumatic, waterproof, firewall door, which could be used to access the engine from within the tank. Source: memoiredeshommes.sga.defense.gouv.fr

Turret

The tank had two different turrets during its development process. The early version had an octagonal faced, frustoconical shape, with the SA35 47 mm gun mounted on the right side and the 7.5 mm MAC on the left. Its armor values are unknown, however, they are probably similar to those of the second design turret. This second design was much more similar to that of the Char B1 Bis, a nonagon with the 47 mm mounted more centrally and the machine gun mounted slightly to the left. The armor was 100 mm all around and 43 mm on the roof. While it can be hard to distinguish the two turrets from one another, the second design has large bulb-like protrusions on the sides for periscopes, which are not shown in many contemporary line-drawings and illustrations. The periscopes were surrounded by thick armor, doubled around the holes, as seen in the blueprints. This turret was designed in August, after AMX had submitted the first design. The reasoning behind why a new turret was made is unknown, and why it was re-done after the tank had been presented.

Several angles of the second version turret. Note the rear hatch for the tank commander. Source: memoiredeshommes.sga.defense.gouv.fr

Armor

The armor on the AMX design was very impressive. To be able to withstand AT fire, the frontal plate was angled at 50° and was 100 mm thick. It is a well-known fact that French tanks had thick armor, but this was another level for 1937. The turret was just as impressive, 100 mm thick angled at 85° all around. The top of the turret and hull were 43 mm thick. To put this in perspective, the Somua S35 had 47 mm of armor at the thickest, while the Char B1 Bis had 60 mm and the Tiger tank – yet to even be conceptualized – was ‘just’ 80 mm all around the turret and not sloped! However, all of this armor came with additional weight and made the 7.25-meter long tank weigh above 45 tonnes, the maximum weight allowed.

Original blueprints of the late turret. Besides the gun, traverse mechanism and more, the extremely thick armored walls of the turret can be seen. Source: memoiredeshommes.sga.defense.gouv.fr

Propulsion

When the tank was designed, there were no engines in production in France powerful enough to move such a heavy vehicle at the required 30 km/h. This meant that completely new engines had to be designed. The tank was to be equipped with two V12 engines with a horsepower of 550 hp (600 hp according to other sources). As per the blueprints, two companies were taken into consideration in the production of these engines; Aster and CLM (Compagnie Lilloise des Moteurs). These engines were to be mounted horizontally along the length of the tank, right behind the ammunition storage. Each engine was coupled to an unknown type of electrical generator connected to two electric engines (total 4, 2 per side) that drove the sprockets. For traverse, each sprocket had a diagonally mounted traverse motor. Neither CLM nor Aster produced such large engines at any point.

Cutout view of AMX 37 showing the V12 Aster motors, however, only one can be seen as they are mounted parallel one to the other. In this image, the crew compartment and other details can be seen. Note the traverse motor mounted diagonally by the final drive. The armor thickness can also be seen.
Front view of the V12 Aster motors. Note the gigantic coil springs from the suspension.
The in-line CLM engines. It was a much shorter alternative compared to the Aster engine however, it was much taller. It is unclear if these engines had fewer pistons, usually in-line engines need to be significantly longer than V shape engines to have the same number of pistons.
Front view of in-line CLM engines. Due to the narrow, tall shape, it is safe to assume these were in-line piston engines. The large plate-like shape over the engines is the radiator, of which this tank had 3. Source for these 4 images: memoiredeshommes.sga.defense.gouv.fr

Suspension

The suspension was very similar to that of the Char B1, with 16 small steel road wheels per track. Two wheels in the front (in between the idler and road wheels) and one in the back (in between the sprocket and road wheels) were not touching the ground and, when tensioned, moved diagonally. This was done to decrease the shock when the tank crossed over large obstacles. On each side, there were 4 large springs connected to a bogie. Each bogie then had two smaller bogies in turn connected to two wheels. In addition, every single wheel had its own spring. This was a very complex system, however, it allowed for a lot of motion from the wheel to the hull itself, meaning that the ride quality would have been rather smooth. At the top of the tracks, 10 return rollers were mounted. This was rather unusual for French tanks, as the Char B1, for example, still used skids.

Cutout showing the suspension layout. This system was very similar to the British Matilda Mk.II tank. The track tensioning system can also be seen.

Aftermath

Despite all the efforts, the Conseil Consultatif de l’Armement rejected all the designs presented by FCM, ARL, and AMX. All three companies presented very complex and expensive tanks, thus limiting their production output to a very small number; making them insignificant on the battlefield. To add insult to injury, every company exceeded the 45-tonne mark, even on paper. The AMX 37 weighed around 50 tonnes on paper, however, a battle-ready tank would have even exceeded this already high number. In response to this issue, the Conseil Supérieur de la Guerre (Eng: Superior War Council) decided on the 26th March 1937 that a much smaller, cheaper yet heavily armored tank be designed. 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 criteria was already under development, and there would not be a need of a new program. This tank was the Char G1.

This was not the end of the road for AMX designed heavy tanks. In February of 1938, the requirements changed. Amongst others, the weight limits were removed. This would eventually lead to the AMX Tracteur C super heavy tanks, but like its predecessor, it remained on paper only.



Illustration of the AMX 37 ‘Char de Rupture’ (Breakthrough Tank), produced by the author, Pavel Alexe, and funded by our Patreon campaign.

Specifications

Dimensions 7.25 x 2.70 x 2.94 meters
(24.6 x 8.9 x 9.65 ft)
Weight 50+ tonnes
(55 tons)
Crew 4 (commander, driver, loader, radio operator)
Propulsion 2 x V12 or in-line diesel engines connected to electrical generators connected to electrical motors
Maximum speed 30 km/h* (18 mph)
Suspension Coil springs
Range 200 km* (125 miles)
Armament 75 mm model 1929
47 mm SA35
4 x 7.5 mm MAC
Armor 100 mm in front hull (3.9 inches)
100 mm side skirts
100 mm all around the turret
43 mm top of the hull and turret (1.7 inches)

*These numbers are what was requested by the Conseil Consultatif de l’Armement . Actual numbers are unknown.

Sources

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