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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
SAE_1957-01-01_570266_EFFICIENCY AND SIMPLICITY IN OFF-HIGHWAY TRANSMISSIONS
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