D1

The Char D1's Renault FT ancestry can still be seen from the sloping engine deck and the profile of the side armour plates; it is also still a rather narrow vehicle, only 2.16 metre wide. Its length is 5.76 metre with tail. The riveted hull armour is thirty mm thick on all vertical surfaces, ten mm on top and bottom. The NC31 introduced a 10 mm protection plate for the suspension units; the lower hull side armour beneath it was probably 16 or 25 mm thick — the exact data have been lost. For its time the Char D1 was relatively well armoured; as a result the hull alone weighs 11 metric tons, rather heavier than a typical light tank of the period. A 74 hp V-4 engine of 6.08 litre renders a top speed of 18.6 km/h; the range is ninety kilometres; it can climb a 110 cm obstacle and a 50% slope, cross a 220 cm trench and wade through 90 cm of water. The type thus had a relatively good mobility for the early thirties. In the hull are two crew members. The first is the driver who, as with the Renault FT, is seated below large double hatches that form the nose plates. He can operate, via a steel cable, a fixed 7.5 mm Reibel machine gun low in the nose, that is almost completely hidden behind the armour. The second crew member operates the radio set on the right side of the fighting compartment, the set being an ER (Émetteur-Récepteur or "emitter-receiver") 51 for the NC31s and an ER52 or 53 for the series vehicles. At the right of the engine deck a very distinctive and robust radio antenna frame is fitted, its point the highest of the vehicle at 2.4 metres. It impedes a full rotation of the turret to the right, limiting the total movement to about 345°. The radio operator also assists in the loading of the gun, by handing over rounds taken from the munition load of 76 to the third crew member, the commander, located in the turret.

As the ST1 turret type had been rejected, a new one had to be developed. Until it was ready all 160 Char D vehicles were temporarily fitted with existing Renault FT turrets, taken from the Renault FT matériel reserve. Two new turret designs were proposed by Schneider. The ST3 was a modification of the ST1. To solve the balance problem, this type had an armoured extension at the back, with a large square opening. The hatch in the back of the main armour could be opened through the square hole of the extension, providing more room for the commander, who, when operating the gun, would still enjoy some protection against small arms fire, without the weight penalty of a larger turret. The matériel commission judged this system, though ingenious, to be hugely impractical — it made the turret more vulnerable in precisely those situations where it was most likely to be hit: when fighting the enemy — and decided to accept the weight penalty, choosing the alternative ST2 that was simply a larger turret that had more room at the back, weighing three metric tonnes. Nevertheless a single pre-series vehicle was fitted with the ST3 for trials and afterwards used in this configuration by the driver school.

This ST2 turret had a very complex geometry with many shot traps. This was partly caused by the large protruding diascopes at the sides, but also a result of forcing the commander to operate in three height levels: he had to stretch himself to observe his surroundings via the cupola, had a forward observation hatch that he could look through while standing in a normal position and had to crouch to operate the 47 mm SA34 gun to the right of him and the coaxial 7.5 mm machine gun to the left. The lower level had its own extension, where extra room had been found in the front of the turret to bring the machine gun forward, while retracting the main gun, thus improving balance even further. Needless to say, the army was very critical of this general arrangement, but it could not be rejected as deliveries were already greatly delayed: the first replacement turrets were fitted only in early 1936.

The ST2, weighing 1788 kg, brought the total weight to fourteen metric tons and, costing 100,000 FF per piece, the total vehicle price to 475,000 FF. The Char D1 was thus neither particularly light nor cheap, causing the Hotchkiss company to propose a design better conforming to the role of mass produced light infantry tank, which proposal would eventually result in no less than three production types: the Hotchkiss H35, Renault R35 and FCM 36. However, even in 1926 the project had been seen as more of a cheaper alternative to the Char B than as a pure light infantry tank; the political situation of the early thirties would force the Char D1 completely into the role of Char de Bataille or "battle tank".

click to read more...