PREPRINT: Subject to revision. Per­ mission to publish this paper, in full or in part, after its presentation and with credit to the author and the Society may be ob­ tained upon request. The Society is not re­ sponsible for statements or opinions advanced in pa­ pers or discussions at its Meetings. #157 570266 EFFICIENCY AND SIMPLICITY IN OFF-HIGHWAY TRANSMISSIONS By THOMAS BACKUS Vice President In Charge of Engineering And C. M. Perkins Development Engineer Fuller Manufacturing Co. For presentation at the SAE NATIONAL WEST COAST MEETING Olympic Hotel, Seattle, Washington August 12-16, 1957 Written discussion of this paper will be accepted by SAE until Sept. 30, 1957. Three double-spaced copies are appreciated. SOCIETY of AUTOMOTIVE ENGINEERS, Inc., 485 Lexington Avenue, New York 17, N. Y. Downloaded from SAE International by University of Leeds, Monday, September 24, 2018Downloaded from SAE International by University of Leeds, Monday, September 24, 2018EFFICIENCY AND SIMPLICITY IN OFF-HIGHWAY TRANSMISSIONS Off-Highway transportation differs from on-highway chiefly in the degree of the adverse conditions to be overcome. The objective is still to move the maxi­ mum load in the minimum time with the minimum expenditure of power. The difficul­ ties to be overcome are much greater in off-highway operations and time is of even greater importance due to the penalty and bonus clauses included in many dirt-moving contracts. This matter of making time is equivalent to obtaining the best possible output of power at the wheels for a given prime mover. This output is largely con­ trolled by the transmission which, besides being inherently efficient, must permit efficient use of the engine by making it possible to keep it operating at or near peak horsepower. At the same time, reliability and ease of maintenance and repair are supremely important. It is of little value to make excellent time on each load if many loads have to be passed up because of down-time due to breakdown and long drawn out complicated repairs. While the history of dirt-moving goes back to antiquity, the science of dirt-moving as we know it today is quite new, since we must date today's type of equipment from the time when people stopped trying to use a tool primarily designed for some other purpose in order to move dirt. We believe it was around 1932 that the Euclid Road Machinery Company which had been manufacturing wagons drawn by Caterpillar tractors decided to build a prime mover designed especially for dirt moving. These trucks used the Fuller 5–A–530 transmissions. This equipment rapid­ ly proved itself to be in a class by itself, and bore only a faint resemblence to the familiar on-highway trucks. A few years later, in 1940, R. G. Le Tourneau de­ signed the first Tournapull, which in basic design was similar to a track-type tractor with the exception that the tracks and driving sprockets were replaced by rubber tired wheels and the heavy transmission having a top speed of eight miles' per hour, shiftable only with the vehicle stationary in the track-type equipment, was replaced by a transmission providing a top speed of fifteen miles per hour and shiftable on the run. The same year saw another innovation in dirt moving when the trains hitherto used in open pit iron mining began to be replaced by trucks. These were Dart trucks, using a combination of the Waukesha engine, American Blower hy­ draulic coupling, and an eight speed transmission. The change which made it possi­ ble to move a large volume of dirt at high speed was the transition to rubber-tired equipment, but the potential high speeds available by the use of rubber tires could not be attained without transmissions which could be shifted on the run and which would provide ultimately several times the speed range offered by the transmissions previously used in track type equipment. The peak efficiency required in order to take full advantage of such equi