Char de Bataille SRA / Renault JZ

France (1921-1925)
Experimental Infantry Tank – 1 Prototype Built

One of, if not the most famous French tanks of the Second World War was the B1 heavy tank and its improved model, the B1 Bis. These large infantry tanks were some of the most heavily armed and armored tanks existing in the world during the late 1930s. While their production only started in the second half of this decade, they had roots going back as far as 1921, with the Char de Bataille program that started a search for a medium, well-armed tank to fill in the void between the small and numerous Renault FT and the gigantic and rare FCM 2C tanks. Within the proposals offered to this program was one designed by the industrial giant Renault, with collaboration from Schneider; the Schneider-Renault A or SRA, also known as Renault JZ.

Estienne and the Char de Bataille

Arguably the most important figure of the first years of French tank development was general Jean Estienne. Nicknamed the “Father of Tanks” in France, Estienne, a major proponent of the use of armored vehicles from 1915 onward, was named the director of the AS (Artillerie Spéciale – Special Artillery), the French armored force, in September of 1916. It is largely thanks to his intervention to the Grand Quartier Général, France’s general headquarters, that the FT light tank reached mass production. Estienne was also a proponent of the Schneider CA1, the first French tank to see service.

At the end of the war, Estienne continued in his role as the leading figure of French armored development. He was still at the head of the AS, which was attached to the French infantry and renamed the Subdivision des chars de combat (Eng: Combat tank subdivision), and he was also named Inspecteur des Chars de Combat (Eng: Combat Tank Inspector). In this position, Estienne had large amounts of power over the future development of French armored technology. With the French military having large quantities of largely effective light tanks thanks to the mass production of the Renault FT, and with the development of large tank already underway at FCM since 1916 with the FCM 1A and then FCM 2C super-heavy tanks, what the French military lacked in his view was an intermediate vehicle between the dwarves and the giants. A ‘Char de Bataille’ (battle tank) was desired, thought of as a vehicle of medium weight that would feature a fixed 75 mm gun able to engage enemy fortifications and positions and to move through the devastated terrain typical of trench warfare in an artillery-saturated battlefield. Estienne thought the type would offer the ideal compromise, mounting an armament capable of knocking out enemy fortifications and trenches, something the FT’s armament of either a machine-gun or a 37 mm gun struggled with while being vastly more reasonable and easier to mass-produce than a monster the size and weight of the 69-tonne, 10-meter long 2C. If successful, the Char de Bataille would have eventually become the workhorse of France’s armored force.

The Char de Bataille program and the Estienne agreements

In 1921, Estienne gathered five of the largest French industrial companies: Schneider, Renault, FAMH/Saint-Chamond, FCM, and Delaunay-Belleville, and gave them the requirements of the Char de Bataille which he requested them to design. The vehicle was to have a weight of 13-tonnes, and feature a hull-mounted main gun: either a 75 mm howitzer with a muzzle velocity of 350 m/s, or the higher velocity 47 mm mle 1902 naval gun, with 750 m/s muzzle velocity. The tank was to have a turret armed with either one or two machine guns. It was to have a power-to-weight ratio of at least 8 hp per ton, and be able to run for 8 to 10 hours. The armor was to be 25 mm thick.

Most importantly, the program was not planned to result in the immediate adoption of the product that answered to the specifications the most. The plan was that, once the prototypes were produced, the most interesting features from each would be taken to then be featured in a new tank design that would not be the property of a company, but of the state. The objective of such a move was to reduce competition and encourage the manufacturers to innovate without the risk of a yet not entirely mastered concept leading to the refusal of a proposal. Once the vehicle that combined the best features of each proposal was adopted, each of the manufacturers involved would play a part in the production. This original policy was named the Estienne agreements.

Schneider-Renault Collaboration: Common features, separate designs

While FAMH and FCM went to design and build their own prototypes in complete independence from other firms, Schneider and Renault decided to collaborate to produce two different prototypes. This collaboration mostly consisted of some major elements of the prototypes being shared by both: notably the turret, designed by Schneider, and the powerplant, designed by Renault.

The design of the vehicles and their manufacturing outside of those two major elements, though, remained independent; the second prototype, the SRB, was designed and manufactured by Schneider, while the first, the SRA, was a product of Renault. It even had a two-letters internal designation code, JZ. The prototype was manufactured in Renault’s facilities of Boulogne-Billancourt, in the western suburbs of Paris.

Interestingly enough, two different photos of the SRA’s hull during manufacturing exist, while the production of other prototypes remains a lot more obscure to this day. This notably shows the vehicle’s suspension without the armored skirts that would otherwise hide it, and make the SRA’s suspension the most well-known of all the Char de Bataille prototypes.

The SRA design: A mostly solid proposal

The tank designed by Renault took the shape of a mostly rectangular vehicle, with two front plates angled backward, the driver’s vision port being featured on the higher one. To the right of the hull front, a 75 mm howitzer was fitted but this solution offered no lateral traverse of the gun. It did, however, leave a great deal of space for the driver, who was now more comfortably accommodated than on FCM and FAMH designs. The vehicle featured two almost square-shaped hatches on each side of the vehicle, under the tracks and between the suspension bogies. The armor was 30 mm at its thickest, on the vehicle’s front. This was an impressive amount for 1925. The SRA was 5.95 m long, 2.49 m wide, and 2.26 m high; it had a ground clearance of 0.40 m; the vehicle’s weight was 19 tonnes.

The suspension and tracks were mounted to the side of this hull. Thanks to photos of the SRA during its production, they are a lot more well-known than on other prototypes. The vehicle had a rear-drive sprocket and a front idler wheel; interestingly enough, this rear wheel was mounted higher than the front one, meaning the highest point of the suspension was at the back of the tank. The suspension featured two bogies of six wheels per side, those being mounted on leaf springs. One bogie was in front and one behind the large escape hatch featured at the middle of the hull’s flank. The tracks used had wooden pads with a high track pitch; they were 53 cm wide. The vehicle could cross a 2.50 m-wide gap.

The engine, which was designed by Renault, was a six-cylinder one based on a bisected 12-cylinder aircraft engine. It produced 180 hp at 1500 rpm. This was 60 hp more than the Panhard 120 hp engine used on the FAMH and FCM. Despite being the heaviest tank in the competition, at 19 tonnes, the Schneider-Renault prototypes also had the highest power-to-weight ratio, with 9.5 hp/ton. The SRA consumed 28 to 35 liters of fuel an hour, and its fuel tanks contained 420 liters, giving an average range of about 140 km. The tank had a maximum speed of 17.5 km/h on a road. The transmission was at the rear. It was an epicyclic transmission, which was intended to provide great accuracy in traversing the vehicle’s hull, adjusting for the complete lack of lateral traverse on the gun. The SRA also had hydraulically actuated brake disks.

The turret featured on the SRA as well as the SRB was of Schneider design. This was a cast design, a particularly modern feature for the early 1920s, with an inclined roof, being at its highest at the rear. The turret had a turret ring diameter of 95 cm, weighed 700 kg, and was armed with two Hotchkiss mle 1914 8×50 mm Lebel machine-guns. Out of the three crew members of the SRA, the commander sat in the turret; it was mostly a command post, and the purpose of its armament was to defend the tank against enemy infantry, while the hull gun would engage static fortifications. The driver sat to the left of the hull, and also operated as the hull gunner; the loader sat behind the 75 mm howitzer, on the right side of the hull.

Trials: A good base design with some lackluster features

The SRA prototype was trialed along with the three others Char de Batailles starting in Rueil, from May of 1924 to March of 1925.

Some considerable flaws of the design were made apparent during those trials. Notably, the epicyclic transmission was not effective in ensuring that the SRA’s hull movements were highly accurate, while the lack of traverse of the 75 mm hull gun demanded very precise traverse. The wooden pads tracks, which were a design element shared by all other vehicles except the SRB, ended up being disappointing and promptly worn out as well. In terms of both hull traverse and tracks, the SRA ended up bested by its Schneider sibling, the SRB, which featured the first model of the Naeder hydrostatic transmission/traverse system as well as metallic, FT-based tracks.

The SRA design did have some notable advantages though. The configuration of the main gun being pushed to the right side of the hull made the vehicle far more comfortable for the driver, who was a lot more cramped on the FCM and FAMH designs, particularly the FAMH. While the wooden trackpads were a mediocre feature, the suspension in itself was judged as quite solid. In general, the SRA was one of the more appreciated designs, though the SRB and its advanced Naeder system and metallic tracks brought more novel features.

Conclusion – A forefather to the B1

Of all the four Char de Bataille prototypes trialed in 1924-1925, the SRA, along with its sibling the SRB, was one of the ones which ended up the most influential to the French army’s future infantry breakthrough tank, the B1.

Most notably, the configuration of the hull, with the gun pushed to the right side, the loader at its rear, and the driver/gunner on the front left, would be the one adopted on the B1, and both vehicles most definitely look related, particularly from the front.

One could argue, though, that the SRA remained overshadowed by the Schneider side of the Schneider-Renault cooperation – the SRB. Indeed, while many of the influential features of the SRA were also present in the SRB – the configuration of the hull was quite similar, notably – the Schneider vehicle featured some advanced elements, particularly the Naeder system, that would be transmitted to the B1. The SRA nonetheless remains one of the most important forefathers of what would become one of the mightiest tanks of France’s army in 1940.

Char de Bataille SRA/Renault JZ specifications
Dimensions (L x w x h)	5.95 x 2.49 x 2.26 m
Ground Clearance	0.40m
Weight	19,000kg
Engine	Renault six-cylinder producing 180 hp at 1,500 rpm
Maximum speed	17.5 km/h
Power-to-weight ratio (in hp/ton)	9
Fuel tanks	420 litres
Average hourly fuel consumption	28 to 35 litres
Range	140km
Suspension	Leaf springs
Trench crossing	2.50m
Crew	3 men (Commander/turret gunner, driver/gunner, loader)
Armament	2 turret-mounted Hotchkiss mle 1914 8 mm machine guns, 1 hull-mounted 75 mm howitzer
Armor	30mm maximum

Sources

Tous les blindés de l’Armée Française 1914-1940, François Vauvillier, Histoire & Collection editions, p 42-43
GBM N°107 (January-February-March 2014), Histoire & Collections editions, “Les voies difficultueuses du char de bataille”, p 45-46, Stéphane Ferrard
Trackstory N°3 : Les chars B, Editions du Barbotin, p 5-7
Tank Archives: http://www.tankarchives.ca/2016/12/char-b-difficult-beginning.html
Char-français: http://www.chars-francais.net/2015/index.php/engins-blindes/chars?task=view&id=684