A report on German wheel-and-track vehicles during WWII, from Tactical and Technical Trends, No. 39, December 2, 1943. [DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]

TRACK-WHEEL VEHICLES Experimentation by Austrian automotive engineers to produce for the German army a dual-purpose vehicle which will be capable of quick conversion from wheel to caterpillar traction is reported in an article sprinted recently in the German technical publication "Wehrtechnische Monatshefte" A translation of the article follows: *         *         * A suitably-built caterpillar vehicle is fully capable of cross-country travel, but has only a limited cruising radius. The caterpillar track cannot be used for travel on highways at great speed without excessive wear and tear. Vehicles on wheels, on the contrary, develop great speed and have a great cruising radius, but are poorly suited for cross-country travel, even when equipped with all-wheel drive. It was quite natural, therefore, to think of creating a vehicle which would be adequate for both cross-country and road travel, that is, caterpillar motion with motion on wheels. Practical development of this idea has for more than two decades been the subject of research and experimentation. To some extent the creation of tanks is closely associated with that development. Worthy of mention in this connection is particularly the Christie type of construction, such as Russia is using for light battle tanks. Unquestionably, however, this principle involves certain technical and tactical disadvantages, due to the fact that the vehicle's crew requires half-an-hour for the work of removing the caterpillar chains, and must leave the vehicle to do this. One of the advantages, however, is that the width of the vehicle remains unchanged. In the Kolo-Housenka tank of the Vollmer type, developed by Skoda, 4 wheels have to be attached from the side, and the method of driving the vehicle into position on blocks involves much additional difficulty. There was an advantage, however, in the simplicity of construction of that type of vehicle, so that these Skoda vehicles were regarded favorably for a considerable period of time. Of real importance were the wheel-caterpillar vehicles of Landsverk, Sweden. The wheel running gear is built solidly into the car, and can be lowered on the outside by means of a spindle joint. Change from caterpillar to wheel operation, and vice-versa, can be effected while the vehicle is in motion. Both, the French and the English have attempted similar types of construction, but due to its practical adaptability for military purposes the Swedish type of construction was considered superior. Under the stimulus of experimentation in other countries, the former Austrian High Command submitted to the Saurer Works (Vienna) a list of requirements for building a caterpillar-tread wheel car. While traveling on wheels, the vehicle was to be adequate for cross-country travel, and the caterpillar treads were to be used only in traversing particularly difficult terrain. This was taken to imply that change from one type of drive to the other could be done from the driver's seat in a few seconds of time. Consequently, since the caterpillar treads are to be used only on special occasions, and since, therefore, the wear and tear to be anticipated was relatively slight, it would be possible to avoid large structural design and thus keep the weight of the car within close limits. The vehicle must be suited for use not only in draft but also for carriage of heavy loads. After many months of trial on level terrain, in mountains of moderate and great height, partly on snowy ground, with and without attached loads, Saurer developed his wheel-caterpillar car RR (Räderraupenwagen) Type 7. The Austrian High Command had made plans for developing this vehicle as carrier, prime mover, and combat car. This car is propelled by a Diesel motor located in front. The motor is operated on the double-gyration principle, and the speed with trailer is approximately 45 miles per hour on wheels and 12 miles per hour on caterpillar treads. Transmission to the driving gear is effected by means of a dry-operated, single-disk coupling. The caterpillar treads are moved by 2-drive wheels located in front. Each tread rests upon 6 uncovered, stamped rollers of sheet-metal. Helical springs are used for the rollers. The joints of the tread are made of alloyed cast steel and linked to one another by specially hardened bolts of chromium nickel steel. The chain cleans itself while in motion. Steering is effected through a differential by braking the movement of the inside tread when taking a curve. The driving gear for use on wheels embodies a number of structural innovations which Saurer had previously found satisfactory upon testing in the construction of truck series. Since it was necessary for wheel driving to provide the necessary clearance for turning of the wheels, the front wheels placed laterally outside the caterpillar tread entailed a corresponding extra width of vehicle; and for caterpillar driving this width has to be reduced sufficiently to enable the car to pass without difficulty through narrow sunken roads. As the wheels are drawn up, they fit close to the body of the car; in fact, the lower part of the wheels in this position does not project beyond the outer edge of the caterpillar tread. Change from one type of drive to the other is effected by an auxiliary motor through a worm gear, without requiring the crew to leave the vehicle. Since the time required for changing is only 4 seconds, there was no attempt to insist on an arrangement for changing from one type of drive to the other while the vehicle is in motion. This helped to simplify the construction and reduce costs. Only the rear axle is motorized when the vehicle is operated by means of the wheel drive. The driver's seat is located by the side of the motor, at the front of the vehicle, so that there is every possibility of modifying the superstructure further back. This vehicle is equipped with a cable winch. Further details follow: Motor . . . . . . . . . . . . 4 cylinder Diesel, type CRDV Continuous output (with brakes) . . . . . . . . . . . 70 HP at 2,000 rpm Gear ratio . . . . . . . . . 4.91:1, 3.03:1, 1.72:1, 1:1, 0.75:1, reverse 4.58:1 Rear axle reduction . . . . . 5.9:1 Tank capacity . . . . . . . . Approx 18 gals Fuel consumption (wheels) . . Approx 5 gals per 100 miles Fuel consumption (treads) . . Approx 2 quarts per mile Dead weight . . . . . . . . . Approx 8,800 pounds Useful load . . . . . . . . . Approx 4,400 pounds Total length . . . . . . . . 14 feet, 3 in Height on treads . . . . . . 5 feet, 3 in Width on wheel drive . . . . 7 feet, 2 in Circumstances did not permit the planned far-reaching adoption of this vehicle in the Austrian Army in 1938. But development of the type is being continued. Comment: Vehicles of this Austrian type were reported by observers as in use by the German Army in the Middle-East theater.

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