1971 Volume 33 Issue 2 Pages 118-127
Traction tests of a tractor which is equiped with “gear replacement type” hydrostatic ransmission (“Taurodyne”) were conducted and following results were obtained.
1. In case of the tractor with a mechanical tra-nsmission, its maximum drawbar pull is limited by 100% slippage or engine-stop.
However, in case of the tractor with hydrostatic transmission, it is limited by 100% slippage at low speed and opening of the relief valve, at high speed.
2. Ground speeds of HST tractor can be varied smoothly and the combination of drawbar pull and ground speed which can not be obtained from the mechanical transmission tractor. is obtainable.
Furthermore, the HST tractor is able to run very slowly.
3. The maximum drawbar horse power of HST tractor (engine output is 42.5PS) was about 21PS and the maximum motor output was about 30PS.
4. When the pump tilting angle is remained constant, the speed ratio reduces with increasing of output torque. This is because the volumetric efficiency of HST reduces with increasing of torque.
5. The maximum transmission efficiencies of HST were respectively 72% (ε=0.25), 66% (ε=0.5), 67% (ε=1.0) when the engine speed was 2, 400rpm.
6. The optimum combinations of engine speed and speed ratio settings to minimize the fuel consumption were obtained and shown in graphs. This results will be useful for the optimum control of HST tractor.
