Assessment of Dynamic Load Equations Through Drive Wheel Slip Measurement

Many parameters such as dynamic load of tractor drive wheels influence the traction of tractors. An increase in dynamic load of drive wheel increases the net traction, but excess dynamic load decreases the tractive efficiency that must be avoided. Development of tractor-mounted implements due to good maneuvering and weight transfer from front axle to rear axle led to effective performance of tractors. Therefore, sufficient knowledge regarding weight transfer phenomenon and dynamic load prediction or measurement is essential. Direct measurement of dynamic load on drive wheel encounters some problems and obstacles. An alternate approach to determine this important parameter is to use prediction equations of dynamic load. In this regard, a research effort was undertaken to choose the best equation. Four equations were considered; in equation 1 dynamic rear wheel load is assumed equal to tractor total static weight, in equation 2 the static rear wheel load and the amount of weight transfer is considered and equations 3 and 4 in which moment effect of front wheel rolling resistance in addition to static weight was taken into account. In this study, the equation given by ASAE Data 497.4 where wheel slip is calculated based on dynamic load was applied. Therefore, the calculated magnitudes were then compared to measured amounts through field tests. Results showed that equation 1 is the most fitting one and a relationship was obtained as the slip predicted by equation 1 is 0.915 of slip measured (R =.99, R.S.E= 0.55). 2