Long before the end of the war and the landing of the Allies in Normandy, a special engineering tank, Churchill Bobbins, was created by British engineers. It differed from other armored vehicles in a large frame on which a drum was mounted for transporting a textile ribbon track. Moving through a complex landscape on its own tracks, such a tank had to unwind the tape and lay it on the ground. It should be used as an improvised road for moving vehicles with insufficient traffic.
The paving tank of the “pavement” partially solved the problem of moving wheeled vehicles over sand and other specific surfaces, but this idea had certain drawbacks. So, to organize a large naval landing operation, a significant number of engineering tanks and allocate special watercraft for their delivery. The organization of the landing would be easier if the wheeled vehicles could have their own means of laying the "road".
In 1948, experts from the United States offered their own solution to the problem. A group of Marine Corps officers who served on Quantico base (pc. Virginia) developed a set of original equipment for mounting on serial wheeled vehicles that can increase its maneuverability by repeatedly increasing the surface area.
As far as we know, the original development received a very simple name that fully revealed its essence - Squirrel Cage (“Squirrel Wheel”). Indeed, the new units of unusual design had to play the role of the wheel itself, whereas the machine equipped with them had to take on the “duties” of the squirrel. In other words, some kind of crawler propulsion was proposed, as part of which the wheeled vehicle was to perform the functions of a cart with rollers and wheels.
As follows from the available data, the first version of the “Squirrel Wheel” was developed for use with a light multi-purpose vehicle such as Willys MB. This technique was very popular among the troops, and the creation of special equipment for it could lead to understandable positive consequences. As planned by the authors of the project, the Squirrel Cage system should have been distinguished by the simplicity of production and installation on the car. The latter, however, should not have required major modifications to the basic design.
It was proposed to install a special curved frame made of metal profiles on a jeep. The largest frame elements were the side parts-guides L-shaped section. The front and rear of these guides were rounded with a large radius, while the central ones were made straight. A pair of curved parts had to be connected with two transverse force elements located at the level of the bumpers of the base machine. In the center of this design was located the third curved guide of smaller section and reduced mass.
In the front and rear sections of the resulting frame it was proposed to install the shafts with wide rollers. A pair of rollers was inside the construction, the second - outside with respect to them. In addition, in these parts of the "Squirrel Wheel" were placed mounting, with which the entire structure was to be installed on the production car.
It was suggested to increase the bearing surface of the machine with the help of a metal grid that performs the functions of a caterpillar. The project envisaged the use of a grid with medium-sized cells woven from sufficiently strong wire. The side edges of the mesh were reinforced with metal ribbons. With equal intervals on the grid were installed transverse rods, which provided the required rigidity of the resulting tape. At the same time one of the rods served as a lock connecting the two ends of a rectangular grid.
It was proposed to hang the reinforced net on the frame installed on the car, to pass under the wheels and then join into a continuous tape. The base frame of the system was distinguished by a small height and was in working position directly above the roof of the car. For obvious reasons, when using the Squirrel Cage system, the crew of the jeep should have raised the roof. Otherwise, they risked a hail of sand, mud, or pebbles raised by a mesh ribbon.
Being inside a looped net, Willys MB or another vehicle could move forward or backward. At the same time the wheels, running into the nearest part of the grid, had to pull it in the right direction. The result was a kind of soft caterpillar with frictional engagement of the drive wheels. The lower branch of such a caterpillar hung in the air or lay on the ground, while the upper one moved along the three guides of the main frame.
The presence of the grid, reinforced with transverse rods, allowed in the most noticeable way to increase the area of the supporting surface, complementing the contact spots of the wheels. The car in the “White Wheel” was no longer afraid of sand or any other difficult surface, and its crew and passengers could count on a quick overcoming of the beach.
Not later than the autumn of 1948, the Quantico military base built a prototype of the Squirrel Cage system, designed to be installed on the Wilis car. One of the available cars was soon equipped with new equipment and sent for testing. Running a jeep with the "Wheel" was carried out at one of the nearest polygons. In addition, some further tests were carried out on nearby beaches. In this case, the potential of the structure was tested in the context of use with the amphibious technology.
From the point of view of terrain "Squirrel wheel" proved to be the best way. Despite a certain flexibility and bending in the horizontal plane, the grid correctly lay under the wheels and increased the bearing surface. Using such a "caterpillar", the car could drive on muddy dirt roads, sand, etc. Installation and disassembly of the frame with the grid did not take much time and did not lead to a serious difficulty in the operation of equipment.
However, it was not without serious problems. The main drawback of the Squirrel Cage product was the lack of maneuvering capability. Driving wheels of the car were constantly on the tape, not distinguished by high transverse flexibility. As a result, turning the steering wheel could not lead to real results. At the same time, there was a risk that the tape would skew and even become jammed.
The inability to maneuver could also lead to other problems. For example, a fairly large bump could cause the car to deviate from the intended route and prevent further movement or even lead to a collision with another technique that runs parallel to the course.
Finally, the need to rewind a rather heavy mesh, sliding along metal guides, led to increased engine loads, but did not allow for high speed. The car with the Squirrel Cage system was moving through mud or sand faster than without it, but high speeds comparable to those on the highway were unattainable.
With such problems, the “Squirrel Wheel” system could only be used to land on difficult terrain and quickly pass through it. For further movement, the crew of the car would have to drop the net, pulling out the connecting rod, and then moving down from it. Thus, the original project, in general, solved the tasks assigned to it, but could only do it with some restrictions. Proper organization of the operation of such systems allowed, to a certain extent, to reduce the negative impact of these factors.
Soon the Squirrel Cage project was redesigned to meet the requirements of other serial equipment. The second carrier of this system was the wheel amphibious amphibious DUKW. Modification of "Wheels" for such a machine had some differences from the basic version. First of all, it differed in its size, determined in accordance with the dimensions of the amphibian. In addition, a new support frame was used.
The basis of the new frame was a pair of curved side rails of greater width. The front of these guides, curving, rose above the base of the base machine. Behind the front bend there was a flat horizontal section. Then another bend followed, followed by a second horizontal element. Between the side guides connected by several transverse beams. In addition, between them were three lightweight guides. The longitudinal and transverse elements were connected with low inclined racks attached to the roof of the DUWK amphibious hull.
The front of the frame has lost the rollers to hold the grid. In this case, three inclined beams appeared under it, with the help of which a part of the mass of the frame was transferred to the frontal part of the body. The grid, on the whole, has not changed. I had to use a wider "track tape", but the grid cell size remained the same. At the same time, longer and thicker transverse rods were needed.
Prototypes "Squirrel wheel" on the test. In the foreground is a jeep with networking tools. Behind - amphibian, leaving the prepared "road". 1 December 1948
Despite the solid processing of the structure, such a version of the Squirrel Cage was almost no different from the basic version for jeeps in its capabilities. There were the same benefits and the same limitations. However, gain in cross-country ability could completely level all the characteristic problems.
The “squirrel wheel” for the DUKW amphibian was distinguished by an understated rear section of the frame. This feature of the design could be the result of a new original proposal. At a certain point, the authors of the project conceived of using the technique with the Squirrel Cage system as a pavement handler. In this configuration, a drum should be placed in the back of the frame for transporting a long-length mesh.
When leaving the predetermined area, the paver had to throw the free end of the net through the front part of its frame and run into it. Further forward movement led to the winding of the net from the drum and its laying on the ground. Thus, the palletizing machine, using the basic principles of the original design, not only moved on a complex surface, but also left behind itself the road for the passage of other equipment or infantry.
It is known that in the fall and winter of the 1948 of the year, tests were conducted on a similar handler built on the basis of the Willys MB car. There is no exact information on this score, but it can be assumed that the carrying capacity of the entire 250 kg, part of which was also spent on transporting the frame, would not allow a large supply of tape to be taken on board and equip a long road for one trip. It was possible to get rid of such a problem with the help of another basic chassis. For example, the amphibious DUKW could take on board more than 2 t payload.
Tests of several prototypes of Squirrel Cage systems, built on the basis of serial wheeled vehicles, were completed no later than the beginning of the 1949 of the year. According to the results of the inspections, all the necessary conclusions were made, and the specialists of the armed forces made their decision.
Despite the obvious advantages, the commanders considered the proposed system for increasing the maneuverability insufficiently perfect for practical use. The frame and the grid took away a significant part of the load capacity of the machine, did not allow to maneuver, and also had some other drawbacks. The paving machine was also considered unpromising. As a result, the “Squirrel Wheel” system was not accepted for service, and at the beginning of 1949, all work on this project was abandoned.
It should be noted that this decision of the command did not have a negative impact on the further development of the fleet equipment of the army and the ILC. By this time, several projects were launched to create advanced tracked armored vehicles for the transport of personnel. Protected tracked vehicles with high on-land maneuverability and ability to navigate in water did not need additional facilities like the Squirrel Cage. Thus, the further development of military technology using the already known and mastered technologies made the original project simply unnecessary. In the future, American designers did not return to such ideas.
Squirrel Cage for Jeep // The Day, November 11, 1948.
Squirrel Cage // Mechanix Illustrated, February 1949.