At the end of 1914, the French engineer Louis Boirot developed an original engineering vehicle designed to overcome enemy wire obstacles. The project was based on the principle of a caterpillar propeller, but it was used in a very unusual way. The result of the design work was the appearance of a prototype of an unusual appearance, which failed to interest a potential customer in the face of the French army. Despite the first refusal, L. Boirault continued to work, which resulted in the emergence of an engineering machine called Appareil Boirault No. 2.
Recall that the first version of the preliminary design of the engineering machine Appareil Boirault ("Boirot Device") appeared in December 1914. L. Boirot's proposal was to equip a promising all-terrain vehicle with an original chassis based on the idea of a caterpillar propeller. Using large frames that serve as track links, such a machine had to literally crush wire barriers, making passages for its infantry. To increase the width of the passage, the designer used an unusual layout of the machine with a large propeller size and a relatively small central unit that served as a hull with a power plant and a driver's cab.
Appareil Boirault # 2 prototype on trial
The Appareil Boirault project was completed by the end of the spring of 1915. The documentation for the engineering vehicle was presented to the army. The specialists of the armed forces got acquainted with it and made their decision. The proposed sample could not have high speed and maneuverability, which is why further work on the project was considered inappropriate. Nevertheless, L. Boirot was able to convince the military of the need to continue work and build an experienced all-terrain vehicle. After that, the project was corrected taking into account the comments of the military, and then the assembly of the prototype began.
The prototype "Device Boirot" went for testing in early November of the same year. On November 4 and 13, two stages of testing took place, during which the prototype showed its mobility and the ability to overcome various obstacles. The machine successfully crossed wire barriers and crossed trenches with funnels. However, the speed did not exceed 1.6 km / h. The real indicators of mobility and the absence of any protection for the crew or vital units led to the corresponding decision of the army. The French military refused to support further work, which should have led to the closure of the project. Later, the prototype, which had remained in storage for some time, was disposed of as unnecessary.
The French army, having familiarized itself with the first prototype of the Appareil Boirault machine, refused to purchase such equipment. The military was not satisfied with the low speed of movement, unacceptably poor maneuverability and the lack of any protection. In addition, the first draft did not involve the use of weapons. In its current form, the engineering machine had no prospects. However, the author of the original project did not give up and decided to continue the development of special military equipment. He took into account all the claims expressed and developed a new version of the all-terrain vehicle, more adapted for operation in the army. The new project received the designation Appareil Boirault No. 2 - "Boirot's device, second".
Despite all the claims of the military, L. Boirot considered both the principle of movement itself and the original architecture of the chassis, as well as the vehicle as a whole, suitable for further use. The general layout of the second "Device" should have been preserved, but the various units should have been modified in accordance with the updated requirements related to the possibility of operation in the army. It should be noted that it was not possible to do with minor alterations. In fact, the French inventor had to develop all the main units from scratch, albeit based on existing solutions.
Appareil Boirault # 2 retained the track-based propulsion design. To move across various landscapes and combat non-explosive enemy obstacles, a system consisting of six rectangular-shaped frame sections was to be used. Within the framework of the second project, L. Boirot made the most serious changes in the design of the sections, which led to the appearance of products of different dimensions and modified form. In particular, over time, additional side stops-openers appeared on the "caterpillar".
General view of the left side of the car
As in the first project, the basis of the propulsion frame section was a quadrangular structure assembled from metal profiles and reinforced with kerchiefs at the corners. At the same time, unlike Appareil Boirault No. 1, the new all-terrain vehicle had to have an additional longitudinal beam, reinforcing the frame. On the two ends of the frame, in contact with other similar devices, hinge parts were located. The side beams were equipped with a set of stops, with the help of which the mutual movement of the two frames was limited. The design of the machine was such that the angles between the frames had to remain within certain limits. Going beyond this range threatened to break the chassis and lose progress.
On the inner surface of the frames, along the outer beams, rails ran. As in the previous project, the central unit of the machine, containing the power plant and the driver, had to move along a closed rail track inside the propeller. For this, it had a set of rollers, including those connected to the engine.
The first experimental prototype "Device Boirot" was equipped with a central unit made on the basis of a triangular profile frame. This design made it possible to equip the all-terrain vehicle with all the required devices, but it became a cause for criticism. The prototype did not have any protection, which is why it, by definition, could not be released on the battlefield. In the second project, the inventor took into account the claims of the military, thanks to which the central unit received a reservation, and was also modified taking into account possible combat use.
Since the Appareil Boirault No. 2 machine, according to the creator's plan, was to be used by the army on the fields of the First World War, it had to be equipped with a full-fledged volumetric armored body, the dimensions of which made it possible to accommodate a power plant, transmission, a crew of several people, as well as weapons and ammunition. The solution to this problem was to some extent hampered by the need to use the correct hull shape with a "gable" roof structure. A different structure of the upper part of the hull could lead to contact of the roof with the propulsion elements and their mutual damage.
The result of the design work was a complex-shaped building that can accommodate all the necessary devices and people. The frontal part of the hull was made in the form of a complex multifaceted structure with three frontal plates mounted at different angles to the vertical. On the sides, they were joined by two quadrangular zygomatic leaves, placed at an angle to the horizontal. Behind such a frontal unit was a rectangular main volume formed by two vertical sides and a horizontal bottom. In this part of the hull there were two doors for access to the inside of the car. The stern bore some resemblance to the front of the hull, but did not receive converging side plates. Instead, vertical parts were used, which are a continuation of the central side parts.
Prototype testing
Due to the use of inclined sheets of the forehead and stern, the necessary shape of the upper part of the hull was formed, excluding its contact with the parts of the propeller. At the same time, some transmission parts protruded above the body. To protect them, additional triangular-shaped casings with rounded upper corners appeared over the sides.
A gasoline engine of the available type was located inside the body. The first version of the engineering vehicle was equipped with an 80-horsepower engine, while the power of the power plant of the Appareil Boirault prototype # 2 is unknown. The engine was mated to a mechanical transmission, which included several gears and chains. With the help of the latter, the engine was connected to the driving wheels of the propeller. There were two driving axles with wheels: one was under the bottom of the hull, the other was above its roof.
The undercarriage of the main unit of the all-terrain vehicle had a fairly simple design. Two axles with rollers were attached to the bottom, interacting with the rails of the propeller. Another such axle was on the roof. It is known that some steering mechanisms were used as part of the undercarriage, but the descriptions of their design have not been preserved. In his first project, L. Boirot used jacks to brake one side of the car. How it was proposed to maneuver the "Device" of the second model is unknown.
According to some reports, the Appareil Boirault No. 2 engineering vehicle was supposed to carry weapons for self-defense. In the central frontal and stern plates of the hull, two installations for machine guns of the Schneider brand were to be placed. According to other sources, machine guns should have been mounted on installations in the side doors. It is noteworthy that in this case, the engineering vehicle received a certain similarity with the future early British-designed tanks, the weapons of which were installed in sponsons.
The all-terrain vehicle was to be driven by a crew of three. One of them was to act as a driver, and the other two were shooters. For access to their seats, the crew was asked to use side doors. The crew could observe the terrain using a set of viewing slots in different parts of the armored hull.
Engineering vehicle after modification of the chassis, front view
Despite the change in the design of the main units, the principle of operation of the original propeller remained the same. When the engine was running, the central unit-body had to move along the rails of the propeller sections and change their position. Moving forward, the central unit ran into the front section of the propeller and forced it to lower. That, in turn, stretched forward the sections above the body. Initially, it was assumed that the use of six large and durable frames will allow you to crush wire or other obstacles with high efficiency.
Louis Boirot continued to develop his ideas until about the middle of 1916, after which he managed to re-interest the army. By this time, the French command learned about the development of promising armored vehicles in Great Britain and also showed interest in such technology. Appareil Boirault's new project # 2 made us remember the failure of last year, but nevertheless attracted the attention of a potential customer. Soon there was an order of the military department on the construction of a prototype of a new machine.
The prototype "Boirot Device # 2" was built in the middle of the summer of 1916. In August, the car was sent to the test site. As in the case with the previous project, the fate of the car was determined by the results of just two stages of checks, each of which took one day. Inspections at the range took place on August 17 and 20 on the 16th. The first day was intended to determine the capabilities of the machine, and the purpose of the second was in fact to demonstrate the original development to the representatives of the command.
To test the capabilities of the armored vehicle, a track was again prepared that imitated the battlefield. On a relatively flat area of the landfill, wire barriers were equipped, railway tracks were laid, several trenches were dug, and funnels were made, similar to those left after the explosions of shells. During the demonstration on August 20, the prototype Appareil Boirault # 2 was able to overcome the 1.5 km track in about an hour and a half. The original propeller of the machine crumpled the wire barriers without any difficulty, and then ensured the crossing of trenches with a width of 1, 8 m and funnels up to 2 m in diameter. The used course control system showed its efficiency, but its real characteristics were insufficient. The car turned very slowly, due to which the turning radius reached 100 m.
There is information about some modifications of the propulsion unit at one of the stages of the project. In the tests, frame sections were used in their original form, without additional equipment. However, there are several photographs showing the Appareil Boirault no. 2 with a modified chassis. It should be noted that all of them were made in the workshop of the manufacturer. There is no exact information about the shooting time. Apparently, after the first tests, it was decided to modify the original propeller in order to somewhat increase the parameters of the machine.
Improved prototype, aft view
All new improvements consisted in the use of additional lug lugs. The reinforcing gussets of the section frames now have rectangular details that extend beyond the original reference surface. This could, to a certain extent, increase the area of the vehicle's support, improving its cross-country ability and mobility. Nevertheless, as can be judged from the surviving data, this version of the engineering vehicle was not tested at the test site and did not go beyond the assembly shop.
The reason for the refusal to test equipment with an improved propeller was the results of the demonstration on August 20, 1916. The event was attended by General Henri Joseph Eugene Gouraud, who got acquainted with the original development and criticized it. The general admitted that "Boirot's Device No. 2" is capable of crushing everything in its path. But at the same time, he doubted the possibility of the correct exit to the intended goal. Low maneuverability sharply reduced the real fighting qualities of equipment. In addition, the general noted that the tests carried out are not convincing, since the test track for testing the vehicle very poorly reflects the realities of the front of the current war.
Tests of the second engineering machine by Louis Boirot again showed the design's efficiency, at the same time demonstrating its unsuitability for practical use. Criticism from the command deprived the original development of any real prospects. The army did not want to order the proposed equipment and refused to help with the further development of the project. The designer was forced to stop working. Like its predecessor, the Appareil Boirault Prototype # 2 has been sent for storage. In the future, the no longer needed car was sent for disassembly. None of the prototypes of the original technology survived to our time.
After the second refusal from the military department, L. Boirot stopped working on the development of an original propulsion device capable of overcoming various obstacles and literally crushing the enemy's obstacles. However, he did not lose interest in armored vehicles in general. In the future, the inventor proposed several options for unusual tanks of complex architecture, in which existing samples of armored vehicles and some new equipment were used. These projects were unsuccessful even when compared to Appareil Boirault. For a number of reasons, they did not even manage to get to the prototype stage.
