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On May 28th, 1928, General Estienne informed the Ministry of War of the interest of a powerful tank of 40 to 50 tonnes, with 6 or 7 cm of armor, and equipped with a high velocity 75 mm gun. This tank, which would be called “char d’arrêt”, was favorably received as early as July 9th, 1928 by the Minister as part of the defense of fortified areas. A first approach points out that the armor, in order to withstand tank attacks, should be around 10 cm thick. On the 13th of July, General Estienne had the Forges et Chantiers de la Méditerranée (FCM) study a project on the following bases :
– Railway transport, similarly to the 2C tank
– Armament: two 75 mm guns (700 m/s velocity), with a rate of fire ranging from 12 to 15 rounds per minute
– Speed : about 5 to 6 km/h in cross-country conditions
– Vertical armor: 10 cm on 3 faces, or 15 cm frontal armor with 6 to 7 cm of side armor
The theoretical study takes place, starting from the tank B1 and the tank 2C, with results in mass greater than or equal to 100 tonnes, with such dimensions that the turning capacities are altered. In July 1928, it’s envisaged to have a vehicle in two unsuspended parts, with 10 cm of frontal and side armor, weighing 70 to 80 tonnes, and with a top speed of 6 km/h: a crawler platform (with two electric engines) with double 75 mm gun turret, and a « factory-vehicle » (two generators and two electric engines) fueling the “turret” vehicle thanks to flexible ropes.
Due to the poor practicability of this concept, a second 60-65 tonnes draft was made in August 1928, this time with a single vehicle armed with just one marine 75 mm gun Mle 1922 CA (850 m/s velocity), in the hull, within the axis of the tank, aimed through the tracks, and powered by a Sauter-Harle engine (250 to 270 hp). The maximal armor was 12 cm, and the top speed was 6 km/h.
After studying the two projects, FCM then established a project close to the second one, in agreement with general Estienne. The driving position was double: one to the left of the barrel, with no possibility of aiming, as well as one to the right of the barrel, with the aiming devices. The engine was off-center, thus freeing a way to the rear, leading to a door. The low tracks, first 70 cm wide then 75 cm wide, were covered by the hull, and the suspension is not suspended. Some major changes were still decided, particularly about the frontal armor’s slope, and the ammunition rack getting a higher capacity. The unprotected driving position to the left was removed and became the tank commander’s place, who would have two periscopes as well as observation binoculars. Last but not least a turret armed with a machine gun is projected on the roof, pointing to the rear. The study ended in February 1929, with the tank having the following characteristics :
– Armament: one marine 75 mm gun (850 m/s velocity) with 160 shells, and eventually a machine gun inside a turret
– Mass: about 65 tonnes
– Armor : 10 to 12 cm (sloped front), 5 to 6 cm (vertical sides)
– Speed : 6 km/h
– Effective range: 80 km within 24 hours
On April 26th, 1929, the Minister indicated the credits didn’t allow to consider the realization before 1931. The study was thus stopped on May 17th, 1929, with FCM even accepting to not be paid.
Meanwhile, the Section technique des chars de combat (STCC) establish a rather different draft in June 1929 :
– Armament : one 120 mm gun (400 m/s velocity) in front-mounted turret
– Engine: 500 hp
– Speed : 12 km/h
– Gearbox: Winterthur, hydraulic
– Tracks: FCM type, 75 mm wide, drive sprocket to the front
– Suspension: Johnson with Gall chain
– Mass: about 65 tonnes
– Armor: 50 mm for the gun turret, 35 mm for the MG turret, 50 mm frontal armor, 40 mm side armor, 30 mm rear and roof armor, 15 mm floor armor
Original source: Paul MALMASSARI. Revue historique des armées, n° 234, 2004