[4] 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.
[5] 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.
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 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.
[9] 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.
Encouraged by this, in 1937 he retook the initiative from Poniatowski by, through an intermediary, bribing a high-ranking officer of the Direction de l'Infanterie; the latter again manipulated the commission to change the design policy.
[11] 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.
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.
[12] 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.
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.
Although a petro-electric transmission system was used, theoretically leading to a higher effective power output, tests performed between 3 and 10 December showed that the maximum speed was, as could be expected from the weak provisional engine, a disappointing fourteen km/h on the road, and ten km/h in terrain.
When in July 1938 new specifications called for a main 75 mm armament in the turret, the company was unable to finance a completely redesigned vehicle; the existing prototype could not easily be adapted and its transmission had already shown to be overloaded by earlier weight increases.
On 22 December 1939 it was restarted but merely as a technology demonstrator; at the time of the Fall of France the vehicle was still unfinished and without turret, though it was the only offshoot of the Char G1 project to near completion or even to be in a running condition.
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.
[22] 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.
[7] When the commission issued its changed specifications calling for a 75 mm main gun in a turret, the BDR project threatened to become much too heavy as the hull was already so large.
It transpired on 13 April 1939 that the intended ARL3 turret, bringing the proposed tank's height to 325 cm, could not be fitted without making the design too wide for rail transport, and further that the weight, now projected at 37.5 metric tonnes, would exceed pontoon limits.
A wooden mock-up was all that was finished – and even that could not be shown to the commission because it was for security reasons constructed in an enclosed room lacking a sufficiently large exit;[12] no complete prototype was ever built.
As a result, in late 1937 the project was accepted for service and Lorraine was granted a full development contract for 2.6 million francs, with a prototype to be delivered before the end of 1938.
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.
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.
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.
[29] The specification change of 1 February 1938 was much in favour of Renault, as the other companies needed a very fundamental redesign of their projects to meet the new demands, whereas the ACK1 with its broad fighting compartment could easily accommodate a wide turret as it was.
At this moment however it was recognized by the commission that the weight estimate earlier made by the bribed Infantry officer had been a deliberate falsehood and that the best that could be expected was 28 tonnes.
In April 1938 Renault claimed that weight could be saved by retaining the torsion-bar suspension, limiting the crew to four and keeping the ammunition load to its bare minimum.
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.
[14] As a fallback plan, FCM also was considering the use of the similarly octagonal and welded F4 turret, developed from that of the Char 2C and equipped with the standard 75 mm field gun.
This Commission, not as easily swayed as the previous one as the manipulation by Renault had become known, answered that the prototype could of course be finished as ordered, but that production of the type, despite its interesting advanced technological features, was excluded.
However, in 2008 French armour historian Stéphane Ferrard proposed an alternative interpretation, arguing that the fact that the Renault project was singled out for continued development shows that, had the disruptive course of events not prevented it, very likely the Char G1R would have been taken into production anyway, probably with the ARL 3 turret and a 400 hp engine.