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WW2 French Projects

Jacquet Assault Train

ww2 French Tanks France (1944)
Articulated Vehicle – Design Only

Victor-Barthelemy Jacquet is not a French designer with golden name recognition, like Louis Renault or Colonel Jean Estienne, the fathers of the Renault FT and French tanks respectively. Indeed, virtually nothing is known of him outside of a few patent applications submitted between 1922 and 1944. It is this final patent, submitted at a time when France was being liberated from the Germans by the Allies, which was perhaps one of the oddest tank designs of the war – a train tank or, in modern parlance, a cybernetically connected articulated armored fighting vehicle.

The Man

Little can be found about Victor-Barthelmy Jacquet. What is known is that he submitted his first patent in France in 1922, followed by 7 more filings in Great Britain and France over the next 22 years. His penultimate patent was for this ‘train d’assaut’. His patent filings were technical in nature and showed a degree of engineering mechanical competency, so it is fair to assume that Jacquet at least had a degree of engineering knowledge. When it comes to the ‘train d’assaut’, there are not many clues from which to work for providing additional background on Jacquet, not even his address at the time. However, this was disclosed in the 1922 application in Great Britain for a patent on his reversible motor pump. At that time, he was living at 20 Boulevard de Villiers, Levallois-Perret, right in the heart of Paris. Today, this is a rather anonymous and mundane white apartment block with commercial premises underneath. Where Jacquet may have resided 22 years later is unknown, nor is the reason for the hiatus from 1922 to his next patent in 1943.

A French ancestry site (geneanet.co.fr), which cannot be verified, shows a trace of a Victor-Barthelmy Jacquet born in Montbrison, west of the city of Lyon on 6th December 1883 and dying in Paris on 7th May 1947, aged 67. If that entry is correct, then Jacquet was born as one of 11 children and had served in WW1 (1914-1919). He would have been 31 years old at the outbreak of WW1, and 39 when he submitted that first patent. At the outbreak of WW2, in 1939, he would have been too old for military service at 56 years of age and in 1944, when he submitted this assault train idea, 61.

He is certainly not to be confused with Victor Eugene Alexandre Jacquet from Montbrisson, born two years later (1885) and who died in 1946. That Jacquet was a poet and may have been a relative or just someone sharing a similar name, it is unclear which. If geneanet.co.fr has the correct Victor-Barthelmey Jacquet, then this Victor Eugene Jacquet is not a sibling.

Design

The design of Jacquet’s assault train was simple and complex, all in one package. Simple in theory and complicated in design. The fact that this was as far as it went belied the fact that to put such a vehicle into use would border on the fiendishly complex. Consisting of 3 distinct and different sections, known as ‘cabins’, the design connected all three of them together with a hydraulic coupling allowing for independent movement. In total, this vehicle would amount to some 6 to 7 meters long, with around 0.5 m of ground clearance. Using hydraulic pressure, the coupling could also be locked to assist in obstacle crossing. Each section had its own independent track system and turret.

Jacquet’s assault train, as seen in his 1944 patent application, climbing a short escarpment. The image has been digitally cleaned for clarity.
Source: French patent FR99201

The unusual shape of all three cabins left the leading section angled down and forwards, rather akin to the shape of the bonnet on a car. All three cabins were vertically sided with a rounded upper hull. The turret on cabin 1, mounted in the center of this part of the vehicle, could, therefore cover a very shallow angle to the front – ideal for spraying fire into the steep angle of a trench or for when this leading cabin cleared a slope. It also allowed for the turret on the larger and longer cabin in the middle to overlook the entirety of cabin 1, including its turret, meaning it could also fire to the front as well as to the sides. The third cabin, in the rear, was, like cabin 1, small and angled with a turret operating canted. The angle of the hull roof slope was not as sharp as that on cabin 1. Cabin 3 was also slightly larger than cabin 1 as well. All three turrets followed the same shape.

Harder to tell from the side image was that the leading cabin was also narrower than the main cabin in the middle. This allowed for weapons mounted in the leading edges of this central cabin to fire past the forward cabin.

Front view of Jacquet’s Assault Train. No armament shown in the foremost turret. Modified and adapted from French patent FR99201.

Suspension

All three cabins were tracked, using a relatively straightforward system consisting of a large drive sprocket and a toothed idler at opposite ends of the track. Between these large wheels were what appears to be four double sets of wheels connected together in pairs on either side of a heavy inverted elliptical spring, allowing vertical movement of the bogies. Each bogie was effectively split in two, with one wheel-pair in each piece and the two pieces connected together via a pin, allowing the wheel pairs to move slightly independently of each other. The inner of those two-wheel pairs, consisting of the inner half of each bogie, was connected by another set of leaf springs. To add to the suspension provided by those two sets of elliptical springs, a third set, consisting of half-elliptical springs, was fixed firmly at the top to the hull side and flexibly at the bottom to the foremost wheel on the foremost bogie. The rearmost end of the rearmost bogie was affixed to the hull via a vertical arm and, thus, the entire system could move as one, individually or as bogies. Whilst that is simple enough, albeit far from modern for a tank in 1944 which could be on a more modern system, like volute springs or torsion bars, it was still viable.

The suspension system for each of the cabins of the Assault Train. Note that the tracks are facing left to right. Modified and adapted from French patent FR99201.

Automotive

The center cabin carried the engine and primary gearbox for the vehicle, ensuring that the heaviest mechanical components were mounted close to the center of gravity. From there was a rather complicated system of secondary drive elements to carry power from this primary gearbox to the drive sprockets at the back of the center cabin and, via a long drive shaft, to a powered differential at the rear of the rearmost cabin. Although not shown in the plan view drawing in the patient, the output from the gearbox also went forwards down the center line of the vehicle to the front cabin, to presumably another powered differential at the front of the tracks.

Plan view of the main cabin (right) and the smaller fore or aft cabin (left). The image has been digitally cleaned for clarity. Source: French patent FR99201
Seating position for the crew in the center cabin of the vehicle is shown along with the steering levers. The image has been digitally cleaned for clarity. Source: French patent FR99201

Steering for the vehicle was delivered by means of levers and pedals for braking the tracks, accelerating the engine, and also controlling the hydraulics for moving the cabins in what must have been the most complicated driving job imaginable. This would be made worse by the fact that the driver was positioned high up centrally in the middle section of the vehicle, using the turret for visibility. This meant his view forwards on the ground would be totally obscured by the leading cabin.

Armament and Protection

Protection for all three cabins of the vehicle was provided by a body that was well rounded and made from cast type of steel of either manganese steel or another suitable alloy. Inside this cast steel shell would be the necessary supports, pre-made for the attachment of all of the mechanical components, such as the engine and transmission.

Weapons for the assault train are unnamed but, in his patent application, Jacquet describes how the cast steel body would come with supports cast to hold various components and weapons and any “.. liquids, gases, compressed air, etc., necessary for …. The defense of the assault train”. Whilst some of those elements may also form parts of the propulsion or fuel system, there is clearly also the potential envisaged for at least the use of hazardous liquids and gases for defensive purposes, effectively meaning either something corrosive, poisonous, and/or flammable.

To add to the burden and the otherwise difficult working position of the driver, he would also find himself sat alongside the primary armament of the cabin, which was fitted in the turret.

The rear cabin was designed to house a single 75 mm gun which, very oddly, was pointed directly backward out of the hull of the cabin rather than in the turret. Aiming the gun would therefore be a function of aiming the entire rear of the vehicle at the target. The patent further elaborated on armament by suggesting that other anti-tank guns, machine guns, or a “compressed air mine tube against anti-tank barriers” could be added, without providing any conception as to what that weapon might look like.

As a basic outline of the armament spread across the three cabins and turrets, there would be 4 machine guns and 2 cannons and the drawing clearly shows at least two of those machine guns protruding from the forward face of the central cabin. It is logical to assume that some armament would be mounted in each turret. Given that the leading cabin had the turret so sharply canted, there seems little point in a large cannon in that turret, being so limited in use. A reasonable estimate, therefore, of armament might be for just a single machine gun in that leading cabin’s turret, two in the sides of cabin 2, and a single machine gun in the turret of cabin 3, making 4 in total. With a large caliber gun presumably for firing high explosive shells, like the French 75 mm, in the rear of cabin 3, this would only leave the turret in cabin 2 to find a suitable armament for. Given the small size of the turret and the fact that the driver is also sharing it, whatever cannon or other armament mounted therein would have to be fairly small and would serve to complicate both driving and firing.

Crew

No specific crew is listed or detailed by Jacquet but, based on his drawings and description, an estimate can be made. Only one man was needed to drive the vehicle (cabin 2) along presumably with a commander – again, best positioned in the turret of cabin 2, and therefore probably having to operate the gun as well. At least one other crewman would be needed in cabin 2 to operate the hull machine guns on one side and two men if both were to be operated at the same time, for a total of 3-4 men (commander, driver, machine gunner x 2) in cabin 2.

Cabin 1, with no driving to do, would need at least one man to operate the gun and possibly a second to assist with loading or observation (machine gunner, assistant). The same is true in the rearmost cabin (cabin 3), with the added complexity of the large field gun which would need at least two men to operate so that it could be loaded, aimed, and fired with any degree of alacrity. That would mean not less than 3 and more likely 4 men (turret machine gunner, field gunner, two loaders) there. This means that across the three cabins, at least 8 and maybe as many as 10 men would be needed to operate the entire vehicle.

Articulation

This was certainly not the first articulated fighting vehicle concert. The first of the modern era was from British Colonel R. E. B. Crompton in 1915, with two tractors connected back to back in an effort to make a longer tracked vehicle for crossing trenches. It is this obstacle crossing ability which was, and still is, appealing to designers of articulated vehicles, like the plan for a set of additional tracks on the front of the St. Chamond in WW1, Delahaye’s 1918 design for a multi-tracked articulating vehicle, or the design for connecting a whole series of tanks together from M. Boireaux in 1936. They all used this characteristic to dramatically move one set of tracks from the other to increase the mobility of the vehicle over rough terrain or obstacles.

It is not known if Jacquet knew of some or any of these preceding ideas or not or if this was just a case of convergent thinking. Either way, the outcome was the same – using a system of articulation of one or more sections of track, whether independent on a chassis or not, to increase obstacle crossing.

The means by which Jacquet’s vehicle was to cross an obstacle was, much like the other ideas, to use one or more sets of tracks on a body or bodies. For Jacquet, in his three-cabin vehicle, it was the smaller leading cabin that led the way in crossing obstacles and this was achieved with a hydraulically controlled bearing between the cabins, which allowed for both vertical and horizontal movement. Cabin 2, the larger of the three cabins and located in the middle, provided the bulk of the system, with the third cabin at the back acting almost as a tail and balance for the whole lot. Between the cabins were effectively spheres, with a third of the front and rear removed and with the remaining part able to fit into the adjoining piece, giving the appearance of a concertina effect when in operation. For the connection between cabins 1 and 2, this was formed from three such ‘cut spheres’ forming the connection, but only two for the connection between cabins 2 and 3.

The three cabins of Jacquet’s Assault Train seen from above, showing the horizontal movement available to it. Note that the image has been digitally cleaned for clarity.
Source: French patent FR99201

When the system came to a vertical obstacle, such as a wall or even a cliff up to the height of the whole vehicle, it would begin to scale it by elevating the leading cabin hydraulically. Lifting this off the ground and then moving cabins 2 and 3 forwards would push cabin 1 up the cliff. As cabin 1 got to the top, the middle cabin would come off the ground but be hauled forwards by the trailing cabin, helping to provide forward thrust, as well as what traction cabin 1 could purchase at the top of the escarpment. As cabin 1 cleared the top, this tractive effort increased and brought cabin 2 to the top just as cabin 3 started to leave the ground and provided less and less traction.

Diagrammatic cross-section of the leading section of the vehicle, showing the engine and primary gearbox, along with the circles indicating the articulation. The rounded body work is also apparent. Note that the image has been digitally cleaned for clarity.
Source: French patent FR99201

Thus, all the pieces of the vehicle would act in sympathy with each other. As one piece lost traction, the others gained it, balancing out the forces needed. Even in the case of a vertical face, the system could work on paper.

The means by which the tank could climb a sheer cliff face as tall as itself.
Images adapted and modified from French Patent FR907544.

In the case of a wide gap, such as a particularly unpleasant anti-tank ditch, river, or canal, the system still worked. However, instead of elevating the leading cabin of the vehicle, the coupling could be locked and cabin 1 pushed ahead into the gap. As long as the center of gravity of the vehicle was not exceeded in pushing this leading cabin out in the void, the whole train would remain level on the other side of the gap. By the time cabin 1 reached the other side, cabin 2 would be exiting the bank, and cabin 1 would be pulling it across and so on for cabin 2 and cabin 3, with the coupling locked. Assuming that the gap allowed for a small dip onto the facing bank, like crossing a river, then the gap crossable could be even larger than that of the distance to the center of gravity. This relatively small vehicle of three parts possessed a remarkable level of agility which would set it apart from a more conventional design.

Original page from Jacquet’s patent.

Conclusion

Jacquet’s Assault Train swerved headlong into oblivion as a design. Once the basic elements were drawn as they were, Jacquet had committed the vehicle to an impossibly complex drive and hydraulic system to navigate even relatively modest obstacles. Hard to drive, complex to maintain, impossible to command to any effect, the vehicle rightly was as poorly thought-out as it was likely for production or adoption.

Many of the same problems with articulated vehicles which existed prior to this design and which continued to exist thereafter, such as control over the separate sections of the vehicle, how to command and operate it, how to effectively lock and release a hydraulically actuated flexible coupling, were unresolved. Jacquet’s solutions were just like his suspension design – simple in thought, complex in practicality and worse than every other available alternative. There was absolutely no likelihood of this design reaching any stage of trials or production with an armed force as it was laid out. If the technical issues were not bad enough, then the ludicrous number of crew required to operate it should be sufficient to kill it off. A vehicle needing 8 to 10 or more crew was simply never going to be a viable concept when contemporary vehicles fielded by Britain, France, the USA, and the Soviet Union, were 4 and 5 man crews for substantially more tank for the effort.

A slight ray of light for the vehicle was the basic concept of articulation. Whilst it was certainly not new at the time, it was at least clear on how an articulated vehicle of more than 2 sections could have an advantage over a 2 piece design. Namely, a three-piece vehicle could climb even higher obstacles or cross even greater gaps using that third cabin at the back as a tail. Nonetheless, the patent was accepted in July 1951 and quickly filed and forgotten.

5-way vies of the Jacquet Assault Train, showing off the articulated design and the odd turrets.
Front-right view of the Jacquet Assault Train cresting a rise. The advantages of the articulated design are evident.
The same from the rear. All renders done by Giganaut, funded by our Patreon campaign.

Specifications – Jacquet’s Assault Train

Crew: est. 8 – 10 men (driver, commander, machine gunners x 4, artillery gunner, loaders x 2)
Dimensions: 6 – 7 metres long. 0.5 m ground clearance.
Armor: cast steel or manganese or other alloy cast armour
Armament: Optional single 75 mm cannon, anti-tank guns, multiple machine guns, compressed air explosive launcher

References

French Patent FR545918 Moteur rotatif reversible, filed 14th January 1922, granted 4th August 1922, published 4th October 1922
British Patent GB191718 Reversible Rotary Motor or Pump, filed 29th December 1922 – application not accepted.
French Patent FR887564 Dispositif Differential, filed 6th November 1942, granted 16th August 1943, published 17th November 1943
French Patent FR897490 Disposif de changement de vitesse, filed 24th August 1943, granted 30th May 1944, published 22nd March 1945
French Patent FR90371 Machine rotative, filed 6th June 1944, granted 10th September 1945, published 8th April 1946
French Patent FR906066 Motor-thermique, filed 25th July 1944, granted 7th May 1945, published 21st December 1945
French Patent FR99201 Train d’assaut, filed 25th September 1944, granted 18th July 1951, published 24th October 1951
French Patent FR907544 Disposif de transport a patins et roues commandees, field 31st October 1944, granted 2nd July 1945, published 14th March 1946
Forehistoire.free.fr http://forezhistoire.free.fr/56-ph-victor-jacquet.html

3 replies on “Jacquet Assault Train”

An interesting design, although over-complicated for average military maintenance and logistics facilities. The main gun facing to the rear is also unusual, as well as impractible. I can see this concept being used by Sci-Fi wargamers!

I am reminded of the Squat Steam Train that was part of the Warhammer 40K “epic” miniatures system until Games Workshop decided to eliminate “space dwarfs” from that universe. It also was an articulated tracked vehicle with several sections. The rules did not cover any special ability for this vehicle to cross obstacles.

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