THE ROLLING RESISTANCE AND TRACTIVE PERFORMANCE OF A SMALL AGRICULTURAL TRACTOR WITH DIFFERENT SURFACE AND MOISTURE CONDITIONS ON BANGKOK CLAY SOIL

摘要

Cultivations in paddy fields can take place with a wide range of surface conditions and soil moisture which can have a considerable effect on tractive performance and the maximum tractive efficiency that can be achieved. The aim of this research was to investigate the rolling resistance and tractive performance of a small agricultural tractor of 18.7 kW and 0.99 tonnes operating in two wheel drive (2WD) and four wheel drive (4WD) on Bangkok clay soil under different surface and moisture conditions. The four surface and moisture conditions were bare and grass surfaces on soft plastic soil and bare and grass surfaces on hard plastic soil. Torque transducers were fitted to each wheel to measure the longitudinal wheel forces. Wheel slip and drawbar pull were also measured enabling rolling resistance and tractive efficiency to be determined. Experiments were conducted at the agricultural fields and laboratories of the Agricultural Systems and Engineering department, Asian Institute of Technology, Thailand. The highest rolling resistance was observed in 2WD on soft plastic soil with a bare surface, and the lowest rolling resistance was in 4WD on hard plastic soil with a grassy surface. At the same wheel slip, wheel thrust and drawbar pull were highest in 4WD on hard plastic soil, and the lowest thrust was in 2WD on soft plastic soil. The highest maximum tractive efficiency was 62% in 4WD on the hard plastic soil with a grassy surface, and the lowest maximum tractive efficiency was 24% in 2WD on the soft plastic soil with a bare surface.