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With increased tractor horsepowers and drawbar loads, a greater interest in tractive efficiency has been developed. Wheel drives and dual wheels have become quite common on larger tractors as farmers attempt to convert higher engine horsepower into drawbar power. A review of published literature revealed that dual tires were introduced as a means of obtaining better flotation (less sinkage) and possibly better traction under adverse conditions. As many of the tests were made with different sizes of tires and weights, the information obtained was only applicable to the tractor and soil condition tested. The dual tires provided better flotation but did not always increase the drawbar pull. Sauve (8) obtained less pull with duals than with single tires for the same rear wheel weight. This was probably due to the high inflation pressure (20 psi) used in the duals as compared to the single tires (12 psi). Lowering the inflation pressure (on loose surfaces) increased the traction area and decreased the rolling resistance. Later tests by Clark and Liljedahl (2) on model tires indicated that duals performed better than singles (at equal normal weight) in loose soils at travel reductions less than 30%. On firmer soils the duals performed more efficiently when the inflation pressure of the dual tires was below that of the single tire. These results, which were quite valid for the artificial soil they were obtained on, were not verified by the authors in actual field tests.
performance paramaters of tractors equipped with singles, duals and four wheel drive
Domier, K. W. and O. H. Friesen 1969. PERFORMANCE PARAMATERS OF TRACTORS EQUIPPED WITH SINGLES, DUALS AND FOUR WHEEL DRIVE. Canadian Agricultural Engineering 11(1):16-19.
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