The twenty tonne tank By 1935 the French Infantry had not yet developed a satisfactory medium tank. Whereas a reasonably effective heavy breakthrough tank was available, the
Char B1, and several light infantry support tanks were on the brink of being taken into production – the
Renault R35,
Hotchkiss H35 and the
FCM 36 – a good medium tank had still to be designed, as the
Char D1 was a manifest failure and the Char D2 only a slight improvement over its ancestor. Such a medium tank was needed in a minimal number of 250 to serve in the planned organic tank battalion of the five Mechanised Infantry Divisions, the main Infantry force capable of executing strategic offensive or defensive movements. A good medium tank was already under development by the French Cavalry, the
SOMUA S35, but the Infantry rejected this type, both because of technological reasons – its climbing capacity was limited – and because the Infantry wanted to assert its dominance over the Cavalry in the field of tank design. On 18 December 1935 the first specifications were issued by the Infantry for a ''Char Moyen d'Infanterie de 20 tonnes'' ("twenty tonne medium infantry tank"). They called for a tank with a road speed of 50 km/h, an off-road speed of 20 km/h, a range of 400 kilometres, a trench crossing capacity of two metres, a wading capacity of 120 centimetres, a climbing capacity of eighty centimetres and 45° slope, a 47 mm gun and 7.5 mm machine-gun, an armour thickness of 40 mm, a gas-proof hull and the possession of a radio set. The weight limit of twenty metric tonnes was chosen because of railroad, bridge carrying and pontoon constraints. Overall these features were close to those of the SOMUA S35.
New specifications In May 1936, the ''Conseil Consultatif de l'Armement'' accordingly decided that French industry would be invited to initiate studies on the design of a tank having sufficient protection and armament to fight other armour, but light enough (twenty tons or less) to be both cheap and mobile. In October, a special commission revealed to the French industry the changed specifications for the "twenty tonne tank": a maximum speed of at least 40 km/h; a range of 200 km; a protection level equal to that of the Char B1 bis (i.e. 60 mm all around); a trench crossing capacity of 250 cm; a complete protection against gas attack; the dimensions should not impede rail transport and the armament should consist of a high-velocity gun capable of destroying all expected enemy medium tanks, combined with two machine guns. The specifications implied that the vehicle would have been the most potent and modern French tank yet developed. It also entailed that its introduction would not take place in the near future, as it was simply too advanced. This way it was avoided that a decision would have to be reached about the future course the
Infantry tank weapon should take. At the time, there were officers, like
Charles de Gaulle, who proposed that the Infantry raise armoured divisions that were similar in organisation to the
Divisions Légères Mécaniques of the French Cavalry or the German
Panzerdivisionen, i.e. balanced forces with much organic mechanised infantry and motorised artillery, that would be flexible enough to fulfill all possible tactical roles. Other officers however considered it redundant to imitate the
cavalry and thought the
infantry should stick to its proper task: the
break-through only. Some of them wanted that the money to be spent on armoured divisions to instead go to the production of a sufficient number of light infantry tanks to give each division its own organic battalion, as the best way to ensure an effective execution of
combined arms tactics. Some wanted only heavy tanks to be built. The Char G, mobile, but heavily armoured enough to function as a break-through tank, only made sense if German-style armoured divisions would be created and a definite decision about its production could only be made when the role-of-the-Infantry debate had produced a clear winner. Despite this uncertainty about its future, the project generated enormous interest among French industrialists, as it had a real potential to become France's main
AFV building programme, leading to large state investments that the industry badly needed during the period of the
Great Depression. In late 1936 and early 1937, seven companies submitted plans:
Baudet-Donon-Roussel; FCM;
Fouga;
Lorraine de Dietrich;
Renault;
SEAM and
SOMUA. The commission issued its report on each proposal on 20 February 1937. For two of these, the report forms the main source of information because they would be discontinued within a year: the SOMUA design resembled a cross between the SOMUA S40 and the
SAu 40 self-propelled gun; it was basically a SOMUA S35 with better climbing capacity. Of the FCM design no details are known but it seemed to have had the general outline of the FCM 36, though with its dimensions about 20% larger and equipped with a FCM F4 fortification turret. Of the other proposals, those of
Baudet-Donon-Roussel,
Fouga and Lorraine de Dietrich were being kept under consideration until further information could be provided about their feasibility. The SEAM and Renault projects were sufficiently advanced to approve the construction of a prototype of each. The last two firms' good contacts with the French military had allowed them to begin design work even before the specifications were officially revealed. In Renault's case, this advantage had turned into a disadvantage when in November the commission had decided that a hull-based 75 mm main armament was to be preferred on instigation of Prince
André Poniatowski, head of a design bureau subcontracted by SEAM, whose proposal unsurprisingly had this feature. The SEAM prototype was to be delivered before 31 October 1937 at a price of 1.2 million
French francs, twenty percent of which was advanced by the state. The new demand for a 75 mm gun in the hull posed many problems for most contenders as in their first designs no room had been provided to mount such a large weapon; it would likely add a mass of two tonnes. The requirement for a 50% increase in armour protection caused another two-tonne weight rise. All designs on 20 February 1937 failed to meet the original twenty-tonne weight limit and were projected at 23–25 tonnes. He convinced the commission that a 75 mm gun in the turret should be not merely an option, but mandatory. This gave Renault an enormous advantage over all his rivals who now were forced to completely redesign their projects, leading to inevitable large and, as Renault hoped, perhaps fatal delays. In late 1937, the project had been renamed
Char G1 and all prototypes then authorised had received an official designation:
Lorraine:
G1L;
Renault:
G1R;
Baudet Donon Rousel:
G1B,
Fouga:
G1F and SEAM:
G1P. The SOMUA and FCM projects were discontinued for being too vague or lacking innovation; also the production capacity of these two companies had already been directed to the manufacture of other types. On 1 February 1938 the ''Direction de l'Infanterie'' issued new specifications, the third major change in the project concept: a maximum weight increased to 35 tonnes, necessitated by the fitting of an L/32 (32 caliber long) 75 mm gun in a turret. At that moment Renault was unable to give any indication about a possible production date; the Fouga and BDR projects seemed to become prohibitively heavy; SEAM thought to be able to commence manufacture in the middle of 1940 and Lorraine in 1941. On 12 July 1938 a much more detailed list of specifications was given. In general they called for a tank that was to be powerfully armed, immune to standard anti-tank guns, and possessing an excellent tactical and strategic mobility. In detail they demanded a long high velocity semi-automatic 75 mm main armament; a 7.5mm machine-gun in the turret that could also serve as an AA-weapon; a machine-gun in the front of the hull or the turret; a minimal ammunition load of a hundred rounds for the gun and thirty magazines for the machine-gun; an empty weight of thirty and a combat weight of thirty-two tonnes. The engine was to be able to be both electrically and manually started, and the tracks were to be fully accessible. An on-road speed capability was required of 40 km/h maximum and 30 km/h average over a long journey, with an off-road capability of 20 km/h. Two fuel tanks were to allow a range of two hundred kilometres or eight hours off-road. The climbing capacity was to be ninety centimetres and 85% on a solid or 65% on a wet slope. The trench-crossing capacity was to be 250 centimetres and the wading capacity, 120 centimetres. For the first time, dimensional limits were included: the width was not to exceed 294 centimetres to facilitate rail transport, and the absolute height of the fighting compartment was not to exceed 120 cm, but yet be sufficient to hold a side-door. As regards specifications for the gas-tight armour, the required thickness remained at sixty millimetres, but a requirement was added that appliqué armour construction techniques not be used, along with a detail requirement that the armour could be cast – with the sections connected by bolts or, preferably,
gudgeons – or electrically welded. A requirement that automatic fire-extinguishers be present also was added. None of the projects in the summer of 1938 could meet these specifications without a fundamental redesign. The commission decided that, given the unfinished state of the project, no definitive decisions could be made. SEAM was invited to improve the prototype by lengthening the hull, fitting a more supple suspension, and moving the fire-proof bulkhead 95 mm to the back to enlarge the fighting compartment, creating more room to operate the 75 mm gun. On 6 June 1937, the project was considered by the
Conseil Supérieur de la Guerre as a possible battle tank to equip the future
Divisions Cuirassées, the armoured divisions of the Infantry. During 1937 and 1938, the company rebuilt the vehicle, changing the suspension and cooperating with ARL to install a 280 hp Hispano-Suiza engine. Pictures show this rebuilt design had six large road wheels per side. Besides the hull armament, the placement of an APX4 turret, armed with a 47 mm SA 35 gun, was ordered by the commission on 24 May 1938, together with the placement of a radio set.
Char G1F In late 1937,
Fouga had not yet submitted a definite proposal. Its initial project, no drawings of which have survived, proposed a system in which the hull gun was traversed by slewing the entire vehicle, just as with the Char B1, but instead of the expensive Naeder transmission as used in the B1 a British Wilson gear box was planned. Another difference from competing designs was that the track return run was low. The commission rejected the use of a Carden-Loyd track, judging it to be too weak. Nevertheless, Fouga obtained an order for the production of a prototype. In 1938 it was estimated that the weight would rise to 35 tonnes if a 75 mm turret was added.
Char G1B Baudet-Donon-Roussel proposed to build a tank with the general outlines of the Char B1, including a high return track run, but with seven road wheels per side that unlike the B1 did not require a daily greasing, instead using sealed
ball-bearings. The track was to have a continuous rubber (Pendelastic) inner lining. It was planned to install an air-cooled
Potez 12V 320 hp engine, placed transversely in the hull. The transmission was petro-electrical and of the Gebus-Roussin type. The fuel tank was to have a capacity of 520 litres. The armament was to consist of a 75 mm SA 35 howitzer in the hull with 70 rounds. In the 1937 configuration, the tank was to have an APX4 turret with a 47 mm SA 35 gun with 102 rounds. As the hull was wide enough to place the 75 mm gun in its middle, the turret should have been moved to the left, but this was forgotten in the proposal, as the commission pointed out.
Char G1L The project of
Lorraine de Dietrich was based on its 1933 design for a light infantry tank. It was low and long with an excellent trench crossing capacity. This however implied there was no room for a 75 mm hull-based gun; its calibre was reduced to 47 mm, which seemed redundant given that it also had a 47 mm gun in an APX4 turret. The track was that of Carden-Loyd and considered too weak by the commission, as with the G1F project. Similarly the initial proposal to fit a Cleveland transmission was seen by the commission as unsuitable, and it was replaced by a Cotal. Renault submitted its initial proposal to the commission on 10 December 1936, soon after the nationalization of the military branch of the company and renaming of that factory to AMX. This did not stop Louis Renault from remaining very active on the field of military design and production though, using the remainder of his company and competing or cooperating with AMX as he saw fit. Quickly a wooden mock-up was finished of the Renault version of the Char G; the project had the factory designation
Renault ACK1. The designation merely indicated the chronological order of Renault's military prototypes, and had no further meaning. Renault's initial proposal was based on the Renault ZM, or
Renault R35. It had a similar smooth curved cast hull to that of
the light infantry tank but was much wider and had six road wheels and double tracks per side – to avoid having to design a new broad track. It had a modern
torsion bar suspension and, like the originally proposed G1L, a (rather outdated) Cleveland transmission. The suspension protection plates formed an integral part with the hull's main armour. The hull was crowned by a flat-domed cast superstructure that superficially resembled a circular conventional turret. In reality however it was at first planned to be fixed; the 47 mm gun was supposed to traverse through a horizontal slit like in a pill-box, rotating on a pivot fixed to the hull floor, a proposal made by Colonel Balland. In a second version of this design by engineer
Jean Restany, the "pseudo-turret" was traversable, but simply carried along by the electrically driven gun-mount; the turret therefore would not have to be equipped with a heavy
gun-mantlet and, not bearing the weight of the armament, could be much lighter. On the right side of the superstructure a vertical cylinder protruded, on top of which a small rotating commander's cupola was fitted, that was armed with dual co-axial machine guns. The superstructure, with the commander/gunner on the right and the loader on the left, had sufficient room to hold a Schneider 47 mm antitank gun that was much more powerful than the shorter 47 mm SA 35 gun equipping the standard APX1 and APX4 turrets. Expecting that this superior firepower would give his design a clear advantage leading to a quick production contract, as had so often happened in the past, Renault was unpleasantly surprised when lobbying by Poniatowski contributed to a change in specifications to the effect that a 75 mm gun had to be carried in the hull. The ACK1 hull was simply too flat for this. To save his project Renault started a strong counter-lobby. Part of this was proposing, already on 10 December 1936, that as an alternative option the turret should hold a longer (at least L/29) main 75 mm armament. It was also claimed that the weight of the projects, 24 tonnes, could be reduced to 19.6 tonnes by limiting the armament to a single gun. The commission in 1937 was hesitant about the torsion-bar suspension, and rejected the Cleveland transmission and double-track feature. It also concluded that weight would be at least 25 tonnes. Nevertheless, an order for a prototype was made, in view of the innovative armament mounting. As the 2.5 tonne pseudo-turret was moved about by the gun barrel, its momentum tended to disturb the sight-laying. This problem was solved in 1939 with the help of APX, which designed a system in which the vertical axis of the gun mount was directly connected to the turret roof. At the same time the troublesome Cleveland transmission was abandoned. Overall the Renault design process in the years 1938 and 1939 was very slow. On 10 September 1939 the Char G1R was the only one of the projects that was to be further developed, probably because the Renault company was exceptional in having reserve production capacity left. ==Turret design==