In 1914-16, the French engineer Louis Boirot worked on projects of original engineering vehicles capable of making passages in non-explosive obstacles of the enemy. The result of these projects was the construction of two prototypes of equipment used in the tests. Due to low characteristics and a number of specific features, both engineering vehicles could not interest the customer in the person of the French army. The original idea was not developed. Nevertheless, L. Boirot did not refuse further work in the field of promising military equipment. In 1917, he presented several projects of tanks with increased cross-country characteristics. In connection with the main design features, they received the general name Boirault Train Blindé.
In previous projects, L. Boirot tried to increase the cross-country ability of the technique by using a caterpillar consisting of several large-size frame sections. Now it was planned to improve the parameters of mobility by changing the general architecture of armored vehicles. The Boirault Train Blindé was supposed to consist of several sections with its own chassis connected by special hinges. Not without irony, it is worth noting that the appearance of such a project was expected: before the start of work in the field of military equipment, Monsieur Boirot was engaged in the creation of various components and assemblies for railway transport.
Layout "Armored train Buaro" of the first model
Forming the general appearance of the "tank-armored train", the French designer rightly judged that the increase in cross-country characteristics cannot be achieved by increasing the supporting surface of the tracks. By that time, it was already known that the growth in the size of the tracked mover could even worsen the characteristics of the equipment. To solve the existing problem, several sets of tracks should be used, placed on separate hulls. The latter should be connected to each other by hinges of a special design.
The main feature of the proposed architecture of armored vehicles was the possibility of mutual movement of the hulls within a certain sector. Due to this, it was assumed that the tank could overcome various ascents and descents, as well as cross trenches, craters and other obstacles without significant problems. In general, a serious increase in cross-country ability was expected, typical of the battlefields of the First World War.
The first project of the Boirault Train Blindé family was planned to be simplified by using a number of ready-made components, the source of which was to be the existing serial armored vehicles. Moreover, as part of the "tank-armored train" should have used two serial tanks of the same model. After a number of minor modifications and the installation of some new components, these vehicles had to be connected to an additional hull section, resulting in a full-fledged articulated tank.
Scheme of the machine, the location of the main units is indicated
The proposed tank consisted of three sections of different designs, connected by special hinges. The front and rear sections of the armored vehicle were supposed to be converted Saint Chamond medium tanks. The central section was designed by L. Boirot from scratch, but with extensive use of parts from existing armored vehicles. In particular, it had to be equipped with the chassis of an already used tank, modified in accordance with existing requirements.
The front section of the Boirault Train Blindé tank of the first model was supposed to retain the recognizable appearance of the Saint-Chamond tank. Provided for the use of several front sheets, installed at different angles to the horizontal and vertical. The central part of the body had a box-shaped structure of rectangular cross-section. It was proposed to modify the stern due to the need to use a hinge. The rear part of the body lost its overhang, instead of which there was now a vertical wall with attachment points for the hinge parts. Used undercarriage with a large number of interlocked road wheels with coil springs.
Model of a tank on "rough terrain"
The central section of the tank was a box-body unit, the front and rear walls of which received devices for connecting to other hulls. Caterpillars ran along the entire length of the bottom. The central one differed from other sections by a reduced length. This design feature was associated with the placement of the minimum required amount of equipment.
The stern section, like the front one, was based on the design of the existing tank, but had significant differences. This time, the hull of the base tank was deprived of the front overhang with the gun mount. Instead, it was proposed to use a vertical front plate with hinge elements. At the same time, the section kept the stern with vertical top and sloped bottom sheets.
In the original version, the Saint-Chamond medium tank was equipped with 17 mm thick frontal armor, 8, 5 mm thick steel sides and 8 mm stern. The roof and bottom were made of 5 mm thick sheets. Detailed information about the protection of the articulated tank L. Boirot is absent, but there is every reason to believe that the design of the armored hulls had to undergo minimal changes and, as a result, maintain the existing level of protection.
Overcoming the trench
The most important feature of the Saint Chamond tank was the use of an electric transmission. Apparently, it was this feature of the project that led to the choice of such equipment as the main elements of the "tank-armored train". The Boirault Train Blindé project involved the dismantling of the 90 hp Panhard gasoline engines found on the base tanks. Together with them, their own power generators were also removed. At the same time, two traction electric motors were retained in the sections, connected to the drive wheels of the tracks. In each of the three sections of the armored vehicle, a pair of its own engines should be placed.
As a means of power supply for six electric motors of three sections, it was proposed to use a common generator set located in the central building. The existing housing of a relatively large volume made it possible to place a 350 hp gasoline engine in the central section. and a generator with the required parameters. The connection of the generator and traction motors was carried out using cables passing through the hinges of the housings. The use of electrical equipment made it possible to significantly simplify the design of the transmission, eliminating the need for shafts through the hinge, and also to give the armored vehicle the required power. In addition, a high degree of unification was achieved in terms of traction motors and their control systems.
Model of the articulated tank Boirault Train Blindé of the second version
The sections of the promising tank were to be connected to each other using two hinges based on the ideas of a cardan transmission. It was proposed to mount supports with grippers-forks on the housings of the sections, capable of rotating around their longitudinal axes. The connection of the two supports was provided using a crosspiece with a set of fasteners. This hinge design allowed the sections to move relative to each other within certain horizontal and vertical sectors. The hinge parts were proposed to be placed in the lower part of the hulls, approximately at the same level with the chassis.
The hinge used provided free movement of the sections within the permissible angles, but in a number of situations this turned out to be a disadvantage. For this reason, shock absorbers with stop functions have been introduced into the design of the articulation mechanism. On the sides of the cardan joint at an angle to the horizontal, spring or other shock absorbers with a movable rod should be placed. The latter was attached to the wall of the front or rear section, and the elastic elements had to be in the central one.
In later versions of the design, the hinge was supplemented with section control systems. For this, it was proposed to use a set of low-power electric motors with drums located in the central section and responsible for winding control cables. By changing the length of the cables connected to other sections, it was possible to adjust the position of the machine units. Such a mechanism, in particular, facilitated maneuvering.
Scheme of possible movements of the section in the horizontal plane
The proposed hinge and some other mechanisms could cope with the tasks assigned to them, but they were placed openly, which in a combat situation could lead to the breakdown of certain parts with a loss of maneuverability or mobility. To protect the hinge and control devices, it was proposed to use armored casings of the original form. L. Boirot developed a system of two curved armor parts, the shape of which was close to hemispherical. One of the parts was attached to the rear wall of the first section, the second - to the front wall of the central body. One hemispherical casing went inside the other, and together they provided protection for the hinge. Due to its hemispherical shape and a set of cutouts, the armored casings allowed sections of the tank to move freely within the permissible sectors.
The widespread use of the units of the existing tank led to the formation of a corresponding armament complex. In the frontal part of the front hull, it was planned to install a 75-mm cannon with the possibility of horizontal guidance within a sector with a width of 16 ° and with vertical guidance from -4 ° to + 10 °. Also, in the front and aft sections, several installations for machine guns of 8 mm caliber should have been placed.
Calculations showed that the length of a promising tank would reach 18-20 m. Other dimensions could remain the same. The preservation of some hull units made it possible to obtain a vehicle width of 2.67 m and a height of no more than 2.4 m. The calculated combat weight of the Boirault Train Blindé tank reached 75 tons. This did not allow counting on a high power density, but the articulated machine architecture. According to the known data, the design of the hinge connecting the sections of the armored vehicle allowed them to move at an angle of up to 30 °. Thanks to this, the tank, in theory, could overcome various obstacles, showing superiority over other armored vehicles of that time.
Overcoming an obstacle by moving sections in a vertical plane
The first version of the "tank-armored train" could be of certain interest from the point of view of technology and possible combat use. However, due to the widespread use of ready-made components, the armored vehicle should have had some noticeable disadvantages. So, the preservation of the existing gun mount of the Saint Chamond tank imposed serious restrictions on firing. With the help of the guidance drives, the gun moved within a not too wide sector, and to transfer the fire to large angles, it was necessary to turn the entire machine. In addition, the use of a modified serial-type tank could lead to the manifestation of new problems.
To correct the existing shortcomings, L. Boirot created a new project based on the same ideas. The second version of the Boirault Train Blindé armored vehicle was also supposed to consist of three sections with different equipment, but differed from the first in the design of the outer sections, the composition of the power plant, weapons, etc. It is noteworthy that when creating an improved project, the French designer retained the existing hinges and their protection. In addition, it was in this project that section position controls were proposed.
In the second project of the "tank-armored train" it was proposed to use the first and third sections of a similar design. Due to this, it became possible to simplify the mass production of equipment while achieving the highest possible performance. Between the two sections with the crew and weapons, a central one should have been placed, containing the main units of the power plant. Two sections of the new version of the tank were to be equipped with improved armored hulls. As part of the housings, parts with a thickness of 16 to 32 mm were used, which made it possible to significantly increase the protection characteristics in comparison with the previous project.
Scheme of the tank L. Boirot of the second version
Frontal projection protection of the improved front section hull was provided by a curved inclined bottom sheet and a large slab placed at an angle to the horizontal. On the sides of them were placed sides, consisting of two parts. The bottom sheet was proposed to be placed vertically, the top - with an inclination inward. In the aft part of the hull there was a unit of increased height, in front of which there was a turret shoulder strap. The latter was located in the center of the body and could rotate within a fairly wide sector. The tower was planned to be assembled from a cylindrical side part and a conical roof.
The hull of the aft section had a different shape. Its turret shoulder strap was shifted towards the stern in comparison with the front section. In front of the turret was a hull assembly of increased height, similar to the corresponding parts of the front section. The stern section, like the other two elements of the armored vehicle, were to receive side screens to protect the chassis.
Traction motors, two in each, were to be placed inside the front and aft sections. The engines were connected to drive wheels placed in the frontal part of the hull. The surviving drawings show the design of the undercarriage. It consisted of large front driving and rear steering wheels. It was also proposed to use large road wheels, limiting the supporting surface of the caterpillar lying on the ground. Between the drive wheel and the large roller, between the guide roller and the rear roller, as well as between the large rollers, it was planned to place nine small-diameter rollers, distributing the mass of the section onto the caterpillar. The road wheels were connected using bogies equipped with a spring suspension.
Front section layout
In the section tower, it was proposed to place a 75 mm cannon or other similar weapons. The frontal and side plates of the hull were also supposed to contain 8-mm machine guns. If work continued on the project, the composition of the weapons could change in accordance with the wishes of the customer, represented by the French army.
The central section of the "tank-armored train" was again intended to accommodate the power plant. Like the previous project, she received a rectangular body with its own power plant and chassis, covered with side screens. Inside the center section was a 700 hp gasoline engine connected to an electric generator. Through cables, through control systems, the current had to go to the traction motors of all sections of the machine. The undercarriage of the central section was similar to the units of other parts of the tank.
In the second Boirault Train Blindé project, the cardan joint was again used. The supporting devices of the two hinges were located in the lower part of the equipment housings. Above the hinges, at an angle to the horizontal, were placed two sets of shock absorbers and section control systems, two for each hinge. Hemispherical hinge covers were again used, consisting of two parts. In connection with the new design of the hulls, L. Boirot decided to place the lower (inner) casings on the walls of the forward and aft sections. The upper casings, in turn, were proposed to be mounted on the central section. This placement of the armor to some extent improved the interaction of parts during the mutual movement of the sections of the tank. The hinges retained their existing capabilities. The sections could move relative to each other at angles up to 30 ° in any direction.
The device of the central section, shock absorbers and drives for controlling the position of the bodies are visible
The increase in the thickness of the armor and the strengthening of the armament led to a natural result. The estimated combat weight of the "tank-armored train" of the second version reached the level of 125-130 tons. It is not hard to guess what the mobility of an armored vehicle with a specific power of the main engine of just over 5 hp could be. per ton and electric transmission, further reducing performance.
Whether projects of the Boirault Train Blindé family were proposed to the French army is unknown. At the same time, the absence of any information about an attempt to implement these projects may be evidence, at least, of a lack of interest in such developments. Both "tank-armored trains" of the articulated structure could not leave the drawings. The reasons for this are simple and understandable. Even by modern standards, a three-section tank with hinges between the hulls, with a combat weight of about 75 tons, is an extremely complex vehicle with dubious prospects. The second version of the L. Boirot tank, featuring more powerful armor and armament, fully retained all the main shortcomings of its predecessor, and also risked getting new ones.
Thus, the original designs of French tanks had only some minor advantages, which were supplemented by a host of the most serious shortcomings. The likelihood that the military would show an interest in such technology tended to zero. One should not count on the construction and testing of prototypes at all. Both Boirault Train Blindé projects remained at the design stage. Later they were put into practice, but it was only about large-scale models of armored vehicles.
The scheme of combining three Somua S35 tanks into an articulated vehicle
According to various sources, Louis Boirot stopped working on articulated tanks already in 1917-18. His developments in this area did not interest the military, which is why the inventor switched to other projects. However, the idea of an articulated tank was not forgotten forever. In the mid-thirties, L. Boirot proposed two new options for the use of "armored trains". At the same time, however, it was now planned to use the hinges only as an aid to improve the permeability of existing types of equipment.
In 1936, the designer proposed a set of tools with which it was possible to combine three Somua S35 medium tanks into a single combat vehicle. The hinges made it possible to overcome larger obstacles and improved the vehicle's cross-country ability. After crossing a trench, funnel, anti-tank ditch or other difficult obstacle, the crews could disconnect their armored vehicles and continue combat work on their own. It was also proposed to connect the two tanks using an additional section with its own power plant. In this case, two S35 tanks were to receive stern attachments for coupling with an additional section. The latter's own engine could further improve the mobility of the tanks.
Use of two S35 tanks and an additional section. Bottom - hinge device
Nevertheless, L. Boirot's new project was not realized in metal either. The idea of using articulated tanks, even after two decades, failed to interest potential users. The original proposal for the temporary connection of independent armored vehicles did not help her either. The ideas of the enthusiastic inventor were too difficult to use in practice and could hardly be of interest to the military.
Perhaps Louis Boirot should not be accused of incompetence or projection. He had to work in very difficult conditions of his time, when no one yet knew what exactly the combat vehicle of the future should be. The search for viable concepts and the development of new ideas during 1914-17 first led to the emergence of two original engineering vehicles capable of literally crushing wire barriers, as well as two projects of articulated tanks with increased cross-country ability. All these projects did not allow France to start rearming its army, but showed which ideas should not be developed due to their lack of any noticeable prospects.
