Light Tank – 1 Prototype Built
The armored force of France’s infantry, typically better funded and larger than the cavalry’s, had, during most of the interwar years, the WW1-era Renault FT, the most produced and arguably most successful tank of the First World War (at least, without a doubt, from the French side). An innovative light tank, the FT was produced in massive numbers and, with the adoption of new tanks being slowed down considerably after the end of the Great War, it proved to be the most suitable vehicle for the French military to settle on. By the 1930s though, the old FT had grown obsolete, and timid attempts to produce some somewhat heavier FT-based vehicles had resulted in the NC and D1, which were not built in numbers sufficient to replace or even substantially supplement the FT.
The 1933 light tank specifications
Anticipating a replacement for the FT would soon be requested by the French military, Hotchkiss offered, in June of 1933, their preliminary design for a light infantry tank – by that point a turretless, machine-gun-armed project. Hotchkiss’s proposal ended up as somewhat of a self-fulfilling prophecy, pushing the French army to establish requirements for a new light infantry tank to replace the FT.
Those new requirements were finalized on the 2nd August 1933. Though their formulation was a result of Hotchkiss’s proposal, they would be sent far and wide to French industrialists, with up to 14 different manufacturers working on a design, including some with little to no past experience. Indeed, the role of replacement of the FT, the French Army’s workhorse, would logically lead to massive contracts, as this was no irrelevant vehicle to replace.
The specifications sent to the various manufacturers were quite detailed, with performance requirements in a number of different aspects. The tank was to weigh 6 tonnes, feature a crew of two, and be armed with either one or two 7.5 mm machine-guns, or a 37 mm cannon. The maximum speed should be of 15 to 20 km/h, the armor 30 mm thick, and the vehicle should be able to run for 8 hours and at least 40 km. A large number of mobility requirements were also made, such as being able to climb a 65% slope, be stable laterally on a 60% one, or cross a 1.70 m wide-trench or ford water 1.20 m deep, among others. Generally, the requirements called for a vehicle very similar to the FT in role and capacities – merely updated to take into account some more modern features.
Batignolle-Châtillon enters in the fray
One of the manufacturers which offered a design for the specifications was Batignolles-Châtillon. A subsidiary of the larger Batignolles, Batignolles-Châtillon was installed in Nantes, western France. Formed in 1917 as the Compagnie générale de construction de locomotives Batignolles-Châtillon (Eng: General Locomotive Manufacturing Company Batignolles-Châtillon), the company’s products were mostly linked to locomotive and wagon manufacturing, but already included some military aspects, such as the carriages of railway artillery pieces.
The first ‘Bat-Chat’
During the mid 1930s, Batignolles-Châtillon expanded its operation to include armored vehicles manufacturing, which is not particularly surprising from a locomotive manufacturer. Proposing a vehicle for the 1933 program was an important aspect of this foray into armored vehicles manufacturing, though it was not the only attempt. The company also simultaneously designed an amphibious tank design, the DP2.
As with most manufacturers, Batignolles-Châtillon offered a plan in 1934. A prototype was ordered to the company, which is quite notable. Only five manufacturers got to the prototype manufacturing stage, with the other four, APX, Renault, Hotchkiss, and FCM, being involved in military affairs to a greater extent and since an earlier point than Batignolles-Châtillon. Batignolles-Châtillon’s light infantry tank prototype would be completed in the early spring of 1935 and delivered to the trials commission of Vincennes on the 5th of April that year.
The Batignolles-Châtillon design weighed in at 11.76 tonnes at the prototype stage. It was notable for some of its construction principles, as the vehicle combined cast construction for its turret and riveted construction for the hull. It was the only prototype produced as a result of the 1933 program to use riveted construction. Despite this combination of casting and riveting, the Batignolles-Châtillon prototype is overall more reminiscent of the fully welded FCM design rather than the cast APX, Renault, and Hotchkiss vehicles.
Hull design and construction
The Batignolles-Châtillon’s hull was notable due to its riveted construction. It featured front plates quite considerably angled backward, particularly for the lower hull and front sides. This front lower hull featured two doors from which the driver, sitting in the hull, would enter or leave the vehicle. The upper front hull featured two vision ports, one behind bulletproof glass and another behind a perhaps more solid steel cover. Vision ports under glass were also found on each of the front sides of the hull.
The vehicle’s hull got quite narrower behind the crew compartment, with the engine having a fairly diminutive size. The radiator was located at the rear, with the exhaust on the somewhat angled rear plates. Overall, and unsurprisingly for a riveted design, the hull used very angular shapes, making it comparable to the FCM 36 in this regard, though the Batignolles-Châtillon arguably made use of steeper angles. The precise dimensions of the hull are unknown, and in general little precise data has emerged from Batignolles-Châtillon’s light tank prototype. The armor thickness itself is also not known, though 40 mm (to meet the expected requirements that were updated in 1934) all-around were likely, and realistic considering the vehicle’s weight. The armor of the hull behind the suspension and on top would naturally have been lighter – if compared to other French vehicles of similar role and weight, likely in the 15 – 25 mm range.
Powerplant and suspension
The Batignolles-Châtillon vehicle’s power plant was a 66 hp Unic diesel engine. There are few additional details available, however, this is a quite weak engine for such a heavy vehicle. With a power-to-weight ratio of 5.6 hp/ton, it is quite likely the Batignolles-Châtillon vehicle would have been quite sluggish, with even the quite slow R35 having 8 hp/tonne. Reaching anything higher than the program’s required 20 km/h appears an unlikely feat for the Batignolles-Châtillon tank.
The vehicle’s suspension consisted of seven road wheels, an independent one at the front, and six grouped in three bogies of two each. On top of those bogies were nine triangular mounting points for the side skirts, on which they would be riveted. The drive sprocket was installed at the front and the idler at the rear. In operations, the bogies would be covered by a side skirt, though the road wheels themselves would remain uncovered.
An original one-man turret
The Batignolles-Châtillon design featured a one-man turret armed with a 37 mm SA 18 main gun and a coaxial 7.5 mm MAC 31 machine gun. All of the vehicles in the program would eventually match this armament, although the Renault and Hotchkiss vehicles were first offered either without turrets or with a turret design fitted with two MAC 31s instead.
It should be noted that an armament of two MAC 31s instead of just one is often mentioned, but there do not appear to be any mount for a machine-gun outside of the co-axial one. It is possible this may refer to a backup machine-gun being stored in the vehicle either in case of the mounted one being damaged or having a failure or of the crew having to leave the vehicle. This was common in the French cavalry but rarer in the infantry.
As with the front hull, the turret featured a large number of visors. Glass-covered vision ports were featured on the front of the turret’s forehead’, towering quite considerably in the rear three-quarters of the design, as well as on each side. Smaller vision slots were found on the sides and front sides.
At the rear of the turret, a spring-loaded rectangular door could be found. It would allow the commander to stick out of the turret outside of combat situations, or to evacuate the vehicle in urgency. The commander would enter the vehicle from the front hull hatches, and not the turret door.
The size of the turret ring, while not known, was most likely 875 mm, as with the APX turrets featured on the APX, Hotchkiss, and Renault designs, and the FCM’s welded turrets. Turret interchangeability was a requirement for the 1933’s program turrets. In any case, the Batignolles-Châtillon light tank had a one-man turret, in which the crew member would occupy the roles of commander, gunner, and loader. Even with a lot of intelligent technical solutions, making such a turret ergonomically viable – especially with an armament heavier than machine-guns, even with a gun firing small shells such as the 37 mm SA 18 – was pretty much in the realm of fantasy. The commander would very likely have been very much overtasked in operations – though this is also no different from all other vehicles of the 1933 program, due to all following the requirements of a vehicle featuring 2 crewmen.
Unsuccessful trials in 1935
The Batignolles-Châtillon light infantry tank was trialed in 1935, from the vehicle’s delivery in April of 1935 onward.
The vehicle did feature some interesting aspects. Notable was that the liberal use of glass-covered vision slots by the designers allowed for very good visibility, superior to that of other proposals for the light infantry tank design. The armor was also judged satisfactory, with the exception of the hull armor behind the suspension, though how vulnerable this section of the vehicle’s hull would be in practice is questionable. In terms of performance, the Batignolles-Châtillons did not at all appear to have been inferior to other candidates.
Where the Batignolles-Châtillon light tank failed, though, was in terms of reliability. Mobility trials of the vehicle were quite the failure. On the 24th June 1935, the tank was unable to accomplish a 50 km drive, with a breakdown requiring repairs. The weak engine was likely an important factor in those failures leading to the prototype being returned to its factory, and receiving some considerable modifications to its suspension.
Modifications and new in vain trials
The Batignolles-Châtillon prototype was returned to its factory following the breakdown in late June, and then received an entirely new suspension, likely due to the old one being lackluster – once again not particularly surprising for a newcomer in armored vehicles design.
It returned to trials with idlers and sprockets that may have been slightly larger. However, those are by far the most moderate changes. Instead of seven, the vehicle now had six, larger road wheels of a newer design, with larger outer rims. Those road wheels were installed, two-by-two, on three bogies of a new, more sturdy design. Those featured horizontal and vertical springs allowing for more extensive movements of the road wheels. The vertical springs were located behind the boggie’s outer structure, on which the side skirt would most likely insert. Four classic rounded return rollers were featured.
This modified prototype was trialed in 1936, from the 20th January to the 1st August. In comparison to its first iteration, the new suspension likely improved the vehicle’s mobility. The gearbox also appears to have been more reliable on this modified prototype. However, the significant issue of poor power-to-weight ratio remained unsolved. Even if the Batignolles-Châtillon prototype had been perfect – as perfect as a two-men infantry tank could be – it is unlikely it would have been adopted at this point, with three of the five prototypes presented in the 1933 program, the Hotchkiss (H35), Renault (R35), and FCM (FCM 36) already having been adopted. Adding yet another very similar vehicle would have been redundant. In general, the quite similar FCM 36 appears to have been superior to the Batignolles-Châtillon in most aspects, although also mounting a diesel engine, the one it used offered a better power-to-weight ratio, and its welded construction would have been sturdier and more durable than the Bat-Chat’s riveted hull and cast turret. The main advantage the Batignolles-Châtillon would have had over the FCM would most likely have been vision, which, while not irrelevant, would still be little in comparison to the advantages offered by FCM’s welded design. Therefore, and while Batignolles-Châtillon appears to have attempted to salvage its design by suggesting outfitting the tank with a more powerful engine – the Batignolles-Châtillon light tank would not be adopted.
Conclusion – An unsuccessful but interesting first foray into armored vehicles design
The Batignolles-Châtillon light tank is quite notable in that it was one of the contenders for the replacement of the Renault FT. Though it would be an unlucky competitor to the R35, H35, and FCM 36, it is still notable that Batignolles-Châtillon, a newcomer in armored vehicle design, managed to have their proposal reach the prototype stage, something only a minority of the 14 manufacturers called upon succeeded in.
This unsuccessful first attempt would not result in Batignolles-Châtillon stopping their foray into armored vehicle design. In the late 1930s, they would continue studying amphibious vehicle design, with the DP2 and later DP3 amphibious tanks. The most famous Batignolles-Châtillon designs are not, however, those from the 1930s, but rather, the firm’s proposed vehicles from the 1950s: the Batignolles-Châtillon 12t, an unlucky competitor to the AMX-13, and, most significantly, the 25t, a lightweight medium tank which gathered some considerable online fame in the last decade. It ought to be noted, however, that no Batignolles-Châtillon armored vehicle would be adopted by the French military, the closest being the Batignolle-Châtillon’s powerplant being an inspiration for that of the AMX-30, which would become France’s standard-issue main battle tank in most of the Cold War.
|Crew||2 (Commander/gunner/loader, Driver)|
|Armament||1x 37 mm SA 18 main gun, 1x MAC 31 7.5 mm machine gun; perhaps an additional, back-up MAC 31|
|Engine||66 hp Unic Diesel|
|Power-to-weight ratio in hp/tonne||5.6|
|Armor||Most likely 40 mm all-around, lighter behind suspension & on top and bottom|
Tous les blindés de l’Armée Française 1914-1940, François Vauvillier, Histoire & Collection editions, p48
Trackstory N°4: R35/R40, Editions du Barbotin, Pascal Danjou
Les véhicules blindés français, 1900-1944, Pierre Touzin
Chars de France, Jean-Gabriel Jeudy