The initial requirement for the Char B1, known as le char de bataille (the battle tank), as drawn up in 1921, called for a 13-ton vehicle with a maximum armour plate thickness of 25mm to be armed with a hull mounted 7.5-cm (2.95-in) gun for infantry support and two machine-guns situated in a rotating turret.
Four companies were invited to build prototypes although it was under the condition that they allow the army to mix and match parts from the various vehicles that were submitted to eventually produce the best possible vehicle. The companies involved were Forges et aciéries de la Marine et d'Homécourt (FAMH), Forges et chantiers de la Méditerraneée (FCM), Delaunay-Belleville and Schneider-Renault. A total of five prototypes were submitted for evaluation of which four were presented at the arsenal Atelier de construction de Rueil (ARL) in May 1924. Schneider-Renault submitted two prototypes, the SRA and SRB.
The Schneider-Renault SRB was chosen as the basis for the new tank along with its steering mechanism, engine and gearbox. The suspension and running gear were taken from the FAMH designed vehicle and the tracks from the FCM prototype. In March 1925 Renault was chosen as prime contractor with Schneider, FAMH, FCM and Delaunay-Belleville all providing work and components as sub-contractors. The final assembly of the vehicle was to take place at the Renault plant in Paris. A contract for the construction of three prototypes was finally placed with Renault on 17th January 1926 but it was not until January of 1929 that the vehicles first began to appear.
The French Army saw the Char B1, as a supplement to light tanks such as the Renault R35. Classed as a medium tank, this vehicle was designed to accompany infantry attacks, tackle enemy tanks if need be, and break into enemy rearward positions.
The prototype weighed 25 tonnes (28 tons) and carried a crew of four who were protected by a maximum of 25-mm (0.98-in) of armour. It was armed with one 7.5-cm (2.95-in) gun situated beside the driver, two hull-mounted, forward-firing machine guns, and two coaxially mounted machine guns in a revolving one-man turret. In October 1930, based upon experience gained in Char B1 tactical trials, studies were initiated for an upgraded char de bataille. Prototype trials continued and by 1935, maximum armour had increased to 40-mm (1.57 in) and weight to 28 tonnes (31 tons).
The German re-occupation of the Rhineland in March 1935 galvanised the Direction de l'Infanterie (Directorate of Infantry), in April 1935, to order the manufacture of 40 Char Bs, up-armoured to 60-mm (2.36 in). These were to be officially designated as Char B1 bis.
Further design work and trials were needed before the tank could accept the heavier armour but in the meantime production proceeded slowly based upon the 1935 prototype with 40-mm armour, with the addition of a cast APX 1 turret that carried a 4.7-cm (1.85-in) SA 34 short-barrelled cannon and machine gun. Only 35 of these Char B1s, as they were called, were delivered before the thicker armour and other improvements were introduced on the upgraded Char B1 bis, which weighed 32 tonnes (35 tons) and mounted a Renault engine boosted to 300 hp (224 kW) to haul the extra four tonnes. The APX 1 turret was exchanged for the similar but thicker APX 4 turret that mounted the superb high-velocity 4.7-cm (1.85-in) SA 35 L/34 armour-piercing cannon. France eventually produced 365 Char B1 bis tanks.
At the same time that the Direction de l'Infanterie made funds available in 1935 for production of the Char B1, it gave instructions for subsequent development of the vehicle to remedy certain disadvantages found in the B1 and B1 bis. The tanks’ sidewalls and tracks had proven vulnerable to armour-piercing shells and practical experience had revealed the distinct disadvantage of aiming the 7.5-cm (2.95-in) gun solely by aligning the tank. The new design would give this gun a mounting with a limited traverse of five degrees each way. During the redesign, the opportunity was also taken to make space for a fifth crewmember, described as a mechanic. The turret and armament of the new vehicle, dubbed the Char B1 ter, remained the same as on the Char B1 bis. In June 1940, after the invasion of France, the only three B1 ter prototypes were loaded aboard a cargo vessel that was unfortunately sunk before reaching its final destination and so no examples of these unique vehicles exist today.
More info and PLENTY of high-quality pictures :
Detailed technical article with even more pictures:
Sorry for not posting more pictures, but they are simply so many good ones that I don't know what to choose! 8)