Abstract
Traction test o f driving wheel tire in the field was conducted and some ground-to-tire coefficients were obtained:
1. A rear-wheel-drive tractor has been provided with telemetry instruments with which to measure drive wheel thrust and slip, when the instrumented tractor was pulled from the behind by a braking vehicle when it was operating.
2. Four different wireless signals generated by the instruments were sent out in FM wave from the telemetry transmitter mounted on the instrumented tractor. The signals were received and discriminated at the manless station and recorded in a data-recorder simultaneously and continuously.
3. It was observed that the instrument was durable, showing high resistance against heavy tractor vibration.
4. Some ζ-s (traction coefficient—slippage) curves were obtained with the test conducted on a grassland, asphalt, and concrete. The description of the curves was considered. Either Bekker's or exponential eguations expressed ζ-s curves with practically enough accuracy.
5. Parameter K in the exponential function ζ=ζmax(1-EXP(-s/K)), in which ζmax is a peak of ζ, may be calculated by: K=-s/ln(1-ζ/ζmax) for a set of discrete data of ζ and s, under the restricted condition of ζ<ζmax. And the data within the region υ<ζ<ζmax and s<s: were recommended for calculation, where υ is determined properly according to ζ-s curve and s0 is the slippage corresponds to ζmax.
6. Parameters in Bekker's and exponential functions and s0 were called ground-to-tire coefficient.
7. Examples of ground-to-tire coefficients obtained with the test of 12.4/11-36 tire on a grassland, asphalt and concrete were presented.
8. It was considered that ground-to-tire coefficients would not change with the practical change of tire size and wheel weight, when tires were geometrically similar and cohesion between ground and tire was negligible.
