A wheel-type tractor, operating in its second gear range and at its full rated rpm, is observed to maintain a steady speed of 1.5 mph when operating under the conditions described herein. Ambient air temperature is 60°F, altitude is sea level. The tractor is climbing a uniform 6.5% slope with a rolling resistance of 65 lb/ton, and it is towing a pneumatic-tired trailer loaded with fill material. The two-axle tractor has a total weight of 60,000 lb, 55% of which is distributed ton the power axle. The loaded trailer has a weight of 75,000 lb. a. For the environmental conditions just described, a manufacturer rates the tractive effort of the new tractor at 60 rimpull horsepower. What percentage of this rated rimpull does the tractor actually develop? The “20 lb of rimpull required ton of weight per % of slope” approximation will be acceptable. Assume traction is not a limiting factor. b. What is the value of the coefficient of traction if the drive wheels of the tractor are at the point of incipient slippage for the conditions just described.
A wheel-type tractor, operating in its second gear range and at its full rated rpm, is observed to maintain a steady speed of 1.5 mph when operating under the conditions described herein. Ambient air temperature is 60°F, altitude is sea level. The tractor is climbing a uniform 6.5% slope with a rolling resistance of 65 lb/ton, and it is towing a pneumatic-tired trailer loaded with fill material. The two-axle tractor has a total weight of 60,000 lb, 55% of which is distributed ton the power axle. The loaded trailer has a weight of 75,000 lb.
a. For the environmental conditions just described, a manufacturer rates the tractive effort of the new tractor at 60 rimpull horsepower. What percentage of this rated rimpull does the tractor actually develop? The “20 lb of rimpull required ton of weight per % of slope” approximation will be acceptable. Assume traction is not a limiting factor.
b. What is the value of the coefficient of traction if the drive wheels of the tractor are at the point of incipient slippage for the conditions just described.
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