WW2 French Prototypes

Batignolles-Châtillon Automitrailleuse à vapeur

France (1937~1940)
Steam-Powered Artillery Tractor? – 1 Built

The country of France is remarkable for having produced some of the oddest and most creative armored vehicles throughout history. Seemingly never content to take the conventional route, France’s tank designers always attempted to innovate in whatever they designed. No company better exemplifies this than La Compagnie générale de Construction de locomotives, or General Company for the Construction of Locomotives, abbreviated as CGCL and better known as Batignolles-Châtillon, after the two companies that merged to form it.

Full of Hot Air

Batignolles-Châtillon was a steam locomotive manufacturer first and foremost. Its first venture into the world of armored vehicles was with a response to the 1933 requirement by the French military for a light infantry tank to replace the Renault FT. Batignolles-Châtillon’s submission, a design which never received a name, was one of five selected to proceed to the prototype stage. The sole vehicle was completed in 1935.

The Batignolles-Châtillon Light Infantry Tank. Source

The construction of the hull of the light tank made judicious use of sloped armor and riveting. The driver was provided with large glass vision ports and the entrance to his position was a set of doors located at the center of the hull front. The tracks were Kégresse type rubber bands. The original suspension design, a spindly leaf spring setup with seven roadwheels and eight tiny return rollers, was replaced after initial trials with a much more robust combination of horizontal and vertical springs, supporting three pairs of two roadwheels and four return rollers.

The Batignolles-Châtillon Light Infantry Tank with revised suspension design. Source

Although it was a competent design for a first-time tank builder, Batignolles-Châtillon’s light infantry tank was not chosen for production, due to being underpowered and unreliable. The company continued to work on armored vehicles through the rest of the pre-war period, designing a set of amphibious tanks that, like their light tank, did not go anywhere. These three projects are usually regarded as being all of the tanks developed by Batignolles-Châtillon until after World War II, outside of which there is little in the historical record.

Fire, Smoke, and Steam

The two photographs of the Batignolles-Châtillon Automitrailleuse à vapeur. Source: Author’s Collection

In November 2020, two photographs came up for sale on which showed a heretofore unknown vehicle being loaded onto a trailer by German soldiers. Its construction appeared to be a strange contradiction of modern and old-fashioned parts. A highly sloped frontal plate, sloped and reverse-sloped hull sides, what looks to be HVSS suspension, and a transmission housing reminiscent of the M4 Sherman, yet with Kégresse tracks. The hull is armored, but the driver’s position is poorly protected, with what seem to be supports for windows which had not yet been fitted. Among those who discussed the photos the consensus was clear: whatever it was, it was certainly French.

With the driver’s compartment so exposed and the main armor plates appearing to be no more than 15 mm (0.6 inches) thick, it was unlikely to be a tank. The engine being at the rear and the driver at the very front, there was ample room in the body of the vehicle for it to be an armored personnel carrier, ammunition carrier, or an artillery tractor. Verification that the photos were probably taken in France is given by the second photo, wherein to the right of the mystery vehicle a turretless Renault R.35 can be seen. The greatest indication of its provenance came from the suspension and tracks. Horizontal spring suspension was quite uncommon prior to the invention of HVSS by the United States, and the only other vehicle which paired this suspension type with Kégresse tracks was the Batignolles-Châtillon light tank.

With no information accompanying the photographs and nothing written on the back, the most that could be inferred was that this was an incomplete French prototype, probably from Batignolles-Châtillon. The photos evidence that it was captured by the Germans after the fall of France in 1940, and show it being prepared to be transported elsewhere for examination. This same fate befell many French prototypes, including Batignolles-Châtillon’s other prototype at the time, the DP3.

One of the photos was published in the second edition of the book Tous les blindés de l’armée française des origines à 1940 by François Vauvillier. Vauvillier identified the vehicle as most probably being the Batignolles-Châtillon Automitrailleuse à vapeur (Steam Armored Car), an extremely obscure project which is known from only one line of text.

The project was initiated under requirements issued by the French military on 29 August and 26 September 1934, however the contents of these requirements are not known. Vauvillier suggests it may have been part of the Automitrailleuse de Combat (AMC) cavalry tank project, which was initiated about the same time and which resulted in the SOMUA S35. It is worth noting that although “Automitrailleuse” translates into English as “Armored Car”, the term is more accurately rendered as “armored fighting vehicle”, and was used to refer to certain wheeled, half-tracked, and fully-tracked vehicles.

The only direct mention of the Automitrailleuse à vapeur is from a statement of the progress of various programs dated 1 July 1937. The relevant section reads:

“Étude terminée. Caisse et train de roulement en montage à la Compagnie des locomotives de Nantes. Les deux groupes moteur Sentinel sont satisfaisants et réceptionnés. Formalités de douanes en cours en vue de l’expédition à Nantes.”

English: “Study completed. Body and running gear being assembled at the Compagnie des locomotives de Nantes [Batignolles-Châtillon]. The two Sentinel engine groups are satisfactory and received. Customs formalities in progress for shipment to Nantes.”

The project was classified as “No.2 urgency”, meaning work on it was subject to the time and personnel available to Batignolles-Châtillon.

Sentinel Waggon Works was a British company located in Shrewsbury which manufactured steam locomotives and steam-powered trucks. In 1933, Sentinel launched a new, compact 4-cylinder steam engine and vertical boiler called the S Type, which would power its S4, S6, and S8 range of trucks, the most successful and best-selling steam trucks in history. This is most likely the type of engine which was selected for the Automitrailleuse à vapeur, and as indicated by the above excerpt, the twin S Type engines had been taken delivery of by 1 July 1937 and were en route to the Batignolles-Châtillon factory at Nantes. The S Type engine was a single-acting, 4-cylinder steam engine which weighed 1,007.5 lb (457 kg) and produced 120 brake horsepower. It was fed by a 255 psi boiler which produced 14 lb boiler horsepower, or, in other words, 14 lbs of steam per hour. The boiler consumed 3 lb (6.6 kg) of coal per hour. A Sentinel truck with this engine carried 165 gallons of water and 727.5 lb (330 kg) of coal, enough water for 60 miles (96.5 km) and enough coal for 180 miles (289.7 km) of running at most.

A Sentinel S4. The boiler was mounted in the cab behind the driver, underneath the smokestack, and the 4-cylinder engine was mounted underneath the chassis, the steam manifold being visible here in silver. Source

Scalded to Death by the Steam

The idea of a steam-powered armored vehicle was not new. In fact, some of the very first tank prototypes from World War I were steam-powered. The idea, however, never caught on, for a multitude of reasons. Steam boilers are bulky and difficult to fit within a vehicle where space is at a premium; increasing the internal volume of an armored vehicle will quickly balloon the weight of the armor as a result. They are also fragile, necessitating they be enclosed within the armor if a vehicle is going to be going anywhere near the battlefield. Most of all, steam engines are demanding to operate, constantly needing to be fed fuel, have the water level monitored, and the valving adjusted. They also require intensive maintenance during downtime. Even for a steam truck, it is a good idea to have a second person to tend to the engine; it would be an absolute necessity for a steam-powered tracked vehicle, as the driver would already have his hands full, literally, with steering the machine.

It is difficult to assess the condition of the Automitrailleuse à vapeur from the two photos that exist of it. There would have certainly been enough time to mount the steam engines between when they were acquired in 1937 and when the vehicle was carted off by the Germans toward the end of 1940, however, it is not clear whether the boilers are installed or not. There are no visible smokestacks, and the vehicle is obviously incomplete in other ways, most noticeably the driver’s area. On the other hand, it can be ascertained from the second photo, from the man standing on top of it, that the vehicle does have a roof over its center section. Perhaps the boilers are buried deep within the center of the vehicle, and the steam engines themselves are at the rear. This would be the most efficient layout for the vehicle, though apparently leaving it with an awkward amount of internal space. The area around the driver is clearly very spacious, but not spacious enough for the vehicle to be an effective personnel or ammunition carrier, especially if an engineer would occupy that compartment as well. The second photo seems to show a bulkhead behind the driver’s compartment, but this may be part of the boiler system. It would certainly be desirable to be able to access the boilers from the crew compartment, lest the engineer be forced to ride separated from the driver, which would have a negative psychological effect on both crewmembers.

It may seem that some of the above conclusions are baseless, however they were formulated upon comparison with another steam-powered artillery tractor, one that was also powered by Sentinel boilers, the Škoda SK 13. The SK 13 was a design built in 1945 for the German Wehrmacht by Škoda in Czechoslovakia. It was a last-ditch attempt to provide motive power to the Axis war machine that was desperately short on oil and artillery tractors. The power plant for the SK 13 came from the Škoda Sentinel, an older model of Sentinel steam truck, predating the S Type, which was built under license by Škoda. The boilers used for the SK 13 were larger than the S Type, and the engines less powerful, making only 70 hp each. The SK 13 was slightly larger overall than the Automitrailleuse à vapeur appears to have been, and considering the amount of space taken up by the proportionally larger boilers, likewise everything rearward of the driver’s compartment on the French machine would have to be devoted to the steam engines as well. It seems, therefore, that the only role this vehicle would be suited to is that of an artillery tractor.

The Škoda SK 13. The Automitrailleuse à vapeur and the SK 13 were the last steam-powered armored vehicles to be built. There are a handful of proposals that post-date them, such as a steam power plant for the M47 Patton, but none that would go beyond the drawing board. Source

Ultimately, the Automitrailleuse à vapeur would be largely lost to history, disappearing into Germany like so many of the more famous French prototypes and probably being scrapped before the end of the war. Only a pair of photos fortunate enough to survive give a face to what would otherwise be an incomprehensible footnote in the history of armored vehicles.


Two Photographs, from Author’s Collection
Tous les blindés de l’armée française des origines à 1940 – François Vauvillier (Revised Edition)

2 replies on “Batignolles-Châtillon Automitrailleuse à vapeur”

Yes, but the trick is fuel. Oil was hard to find and mostly needed to be imported. Coal was available in Europe.

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