Dynamic load and wheel speed ratio effects on four-wheel drive tractive performance

Scope of study. The effects of wheel speed ratio and dynamic load ratio on four wheel drive tractive performance were evaluated. A four wheel drive tractor was constructed to determine the effects of wheel speed ratio, dynamic load distribution, forward speed, wheel slip and soil cone index on four wheel drive motion resistance, dynamic traction ratio and tractive efficiency. Prediction equations for single axle and four wheel drive motion resistance, dynamic traction ratio and tractive efficiency were developed. The equations were used to evaluate the effects of wheel speed ratio and dynamic load distribution on tractive performance and develop recommendations for ballasting and wheel speed ratio for four wheel drive tractors.; Findings and conclusions. Wheel speed ratio should be in the range of 1.0 to 1.03. Front dynamic load should be in the range of 35 to 50 percent. A four wheel drive tractor should be ballasted to produce 50 to 55 percent front static load. Automatic control of either wheel speed ratio or dynamic load ratio is not warranted. Maintaining the proper ballast configuration will produce improved tractive performance.