Char B1 - Development and Production

Development and Production

The Char B1 had its origins in the concept of a Char de Bataille conceived by General Jean Baptiste Eugène Estienne in 1919, e.g. in his memorandum Mémoire sur les missions des chars blindés en campagne. It had to be a "Battle Tank" that would be able to accomplish a breakthrough of the enemy line by destroying fortifications, gun emplacements and opposing tanks. In January 1921 a commission headed by General Edmond Buat initiated a project for such a vehicle. To limit costs, it had to be built like a self-propelled gun, with the main weapon in the hull. To minimise the vehicle size this gun should only be able to move up and down with the horizontal aiming to be provided by turning the entire vehicle. The specifications included: a maximum weight of thirteen metric tonnes; a maximum armour thickness of 25 millimetres; a hull as low as possible to enable the gun to fire into vision slits of bunkers; a small machine gun turret to beat off enemy infantry attacks, at the same time serving as an observation post for the commander and a crew of at most three men. Two versions should be built, the one a close support tank armed with a 75 mm howitzer, the other an antitank-vehicle with a 47 mm gun instead.

The French industry was very interested in the project. In the past this had often led to much non-constructive rivalry. Estienne, who in the war had personally witnessed the dismal effects of such a situation, was determined to avoid a repetition this time. He used his position as Inspector-General of the Tanks to enforce the so-called "Estienne accord" on the industrialists, ordering them to "reach a mutual understanding, free from any spirit of industrial competition". To be allowed to join they had to agree beforehand to relinquish any patents to the Army, which would be free to combine all projects into a single type. In exchange industry were promised very large orders of no less than a thousand vehicles.

On these conditions four projects were started in 1921: two by a cooperation between Renault and Schneider: the SRA and the SRB, one by FAMH (Forges et Aciéries de la Marine et d'Homécourt, better known as Saint Chamond) and the last by FCM (Forges et Chantiers de la Méditerranée), the FCM 21. Renault and Schneider would each get to produce 250 units, FAMH and FCM each 125. A fifth producer, Delaunay-Belleville, of which the project (an improved FT 17) had been rejected beforehand, would be allowed to make 83 tanks; the remaining 167 would be allotted at the discretion of the French State.

On 13 May 1924 the four prototypes were presented at the Atelier de Rueil, where they were compared, each having to drive over a twenty kilometre test course. Immediately it became evident that their technical development had been insufficient, most breaking down; the SRA even started to fall apart. Maintenance was difficult because the engines were inaccessible. All projects used a three men crew but differed considerably in size, form and the solution chosen to laterally point the gun.

The SRA was the heaviest vehicle with 19.5 metric tonnes. Its length was 595 centimetres, its height 226 cm and its width 249 cm. It had a 75 mm howitzer in the right side of the hull and a cast, 30 mm thick, turret with two machine-guns. It was steered by an epicyclical transmission combined with hydraulically reinforced brake disks—during tests this failed to provide the desired precision.

Seen from the front it already was very similar to the final model, but its side view was more like that of the British Medium Mark D, including the snake track-system, with the drive wheel higher than the idler in front. The suspension used leaf springs. A Renault six-cylinder 180 hp engine (a bisected 12V aircraft engine) allowed for a maximum speed of 17.5 km/h; a four hundred litre fuel tank for a range of 140 kilometres.

The SRB was a somewhat larger vehicle, six metres long, 228 centimetres high and 2,5 metres wide. It was nevertheless lighter at 18.5 tonnes, a result of having a smaller 47 mm gun—it thus was the antitank-version. Using the same engine, its speed was accordingly slightly higher at 18 km/h. More limited fuel reservoirs holding 370 litres decreased the range to 370 kilometres. It used an advanced hydraulic suspension system and the hydraulic Naeder-transmission from the Chaize company combined with a Fieux clutch and Schneider gear box. It used modified FT 17 tracks. The upper track run was much higher, creating enough room for a side door on the left.

The FAHM prototype resembled the contemporary Vickers Medium Tank. It weighed seventeen tonnes, was 520 centimetres long, 240 cm high and 243 cm wide. It used a hydropneumatic suspension. Despite a weaker Panhard engine of 120 hp it still attained a speed of 18.2 km/h. Fuel reservoirs of just 230 litres limited its range to a mere seventy kilometres. The 75 mm howitzer was placed in the middle of the hull and steered by providing each snake track with its own hydraulic Jeanny transmission. On top was a riveted machine-gun turret with 25 mm armour.

The lightest prototype was the FCM 21 at 15.64 tonnes. It resembled a scaled-down Char 2C, the giant tank produced by the same company. It was very elongated with a length of 6.5 metres and width of 205 centimetres. A rather large riveted turret with a stroboscopic cupola, adopted from the Char 2C, brought its height to 252 centimetres. Like the superheavy tank it had no real spring system for the twelve small wheels per side. Separate clutches for each snake track allowed to horizontally point the 75 mm howitzer in the middle of the hull. It used the same Panhard engine as the FAHM type and its speed was the lowest of all at 17.4 km/h. However, five hundred litre reservoirs allowed for the best range at 175 kilometres.

March 1925 Estienne decided to base the future production type on the SRB, as regarded the general form and mechanical parts. However, it would be fitted with the 75 mm gun, a Holt-track to be developed by FCM, which company had completed a special research programme aimed at optimising weight distribution, and the FAMH-suspension (later this would again be discarded). Estienne also had some special desires: a track tension wheel should be fitted, adjustable from the inside, and a small gangway from the fighting room should improve the accessibility of the engine compartment. Furthermore the front armour should be increased to 40 millimetres.

In November 1925 Renault was given the order to build a wooden mock-up, that was finished early 1926. On 27 January 1926 it was decided to build three prototypes of what was provisionally called a Tracteur 30, a final design by engineer Alleaume of the Schneider company, cooperating with the STCC (Section Technique des Chars de Combat). The first was to be delivered by Renault, the other two by FCM and FAHM respectively.

The same year the Direction de l'Infanterie in the Plan 1926 redefined the concept of a Char de Bataille. There would be a greater emphasis on infantry support, implying that the antitank-capacity was secondary and no armour increase was necessary. The weight was to be limited to 22 metric tonnes and the speed might be as low as 15 km/h. However, a radio set would have to be fitted to better direct and coordinate its actions; therefore a fourth crew-member was needed.

On 18 March 1927 the contracts for the three prototypes were signed. The hull of first Renault vehicle, made of softer boiler plate instead of armour steel to simplify changes, was in January 1929 finished apart from the armament. It was delivered in March. The separately produced cast turret was delivered on 23 April. The howitzer could only be fitted in April 1930. This prototype was allotted the series number N° 101. N° 102, the production of which FAMH had shifted to Renault, was delivered soon after; in September 1930 FCM delivered N° 103, constructed by the Atelier de Mépanti at Marseille. One of the vehicles was fitted with an alternative 75 mm Schneider gun instead of the 75 mm St Chamond M 21 from FAMH.

Testing on the first prototype had already begun before the other two were delivered, or even its main armament was fitted. It had with 24,750 kilogrammes a weight higher than specified but could nevertheless reach a top speed of 24 km/h. From 6 May until August 1930 the Commission d'Experiences des Matériels de Chars carried out a further test programme on what was now officially called the Char B—the "B" not referring to Bataille but to a general classification code. The commission was largely satisfied with the vehicle, though many smaller problems were detected that had to be improved. The FCM prototype featured several alternative technologies: a Winterthur transmission, a Citroën clutch and a Sulzer diesel engine, later replaced by a Clerget diesel. All of these systems would prove to be more unreliable than the original concept and were ultimately rejected.

The three vehicles were not only used for technological but also tactical experimentations. Together with the Char D1 pre-series they represented the only modern tanks in France and the Army was naturally very interested in what lessons could be learned from them about future warfare, outlining the concept of a Char de Manoeuvre. Neither Char de Bataille nor Char de Manoeuvre are official type designations; they refer to the tactical concepts only.. In October 1931 a small unit was formed, the Détachement d' Experimentation in which the prototypes were united from December, using the Camp de Châlons as a base to see how they could be used in winter conditions. Afterwards they on their own power drove to the Atelier de Rueil for repairs. In September they participated in the Champagne summer manoeuvres as a Détachement Mécanique de Combat; from 4 May 1933 N° 102 en 103 together formed a Détachement d'Engins Blindés to perform tactical experiments in the army bases of Coëtquidan and Mourmelon as part of a motorised light division, followed by comparable experiments in April 1934 at Sissonne. Technical aspects were not forgotten during these tests and it was established they could attain an average road speed of 19 km/h, cross a trench 2,4 metres wide and wade through a 105 centimetres deep stream.

The prototypes were again extensively altered to meet changes in specifications. On 6 April 1934 the first order was made for seven tanks of a Char B1. The "B1" refers to the fact that there were other simultaneous projects to develop improved types: the Char B2, B3 and B B.

The Char B1 was manufactured by several firms: Renault (182), AMX (47), FCM (72), FAMH (70) and Schneider (32). Although it was the main producer, Renault had not exclusively designed the tank. Therefore the official name was not Renault B1 as often erroneously given. It was a very expensive tank to build: the per unit cost was about 1.5 million French francs. In France at the time two schools of thought collided: the first wanted to build very strong heavy tanks, the other a lot of cheap light tanks. Both sides managed to influence procurement policy to the end that not enough tanks were built of either category, to the exasperation of men like Colonel Charles de Gaulle who wanted to build more of the medium Char D2, with a third of the cost of the Char B1 bis, but armed with the same 47 mm gun.