DYNAMICS OF A POWERED DISK IN CLAY SOIL

Experiments were conducted with a single powered disk in a laboratory soilbin containing Bangkok clay soil with an average moisture content of 18% (db) and 1100 kPa cone index. The disk was 510 cm in diameter and 560 mm in radius of concavity. During the tests the disk angle was varied from 20 degrees to 35 degrees, ground speed from 1 to 3 km/h a nd rotational speed from 60 to 140 rpm. The working depth was kept con stant at 12 cm. The vertical, horizontal and lateral reactions of the soil were measured by force transducers. The forward and rotational sp eeds were recorded. It was observed that disk angle, rotational speed and ground speed had significant effects on soil reactive forces and p ower requirement. With a small disk angle, low ground speed, and high rotational speed, the soil longitudinal reactive force was a pushing f orce and became a resistive one at larger disk angles and ground speed s. The soil transverse reactive force increased with an increase of ro tational and ground speed but decreased with the increase of disk angl e, whereas the vertical relative force increased only with the increas e of ground speed but decreased with the increase of rotational speed and disk angle. It was found that the powered disk required the least power at a disk angle of 30 degrees and rotational speed between 80 an d 100 rpm. Increase in ground speed from 1 to 3 km/h increased the tot al power requirement by 31.8%. Upon driving the disk forward, the draf t reduced considerably compared to that of the free-rolling disk. By d riving the disk in the reverse direction, the draft reduced slightly. At a disk angle of 30 degrees, rotational speed of 100 rpm, and ground speed of 3 km/h, the total power requirement of the forward-driven di sk was 65% higher than that of the free-rolling disk. The predicted en gine power of the forward-driven disk, however, was only 21% higher th an that of the free-rolling one owing to the more efficient power tran smission through the PTO, as opposed to the drawbar. The effects of re verse driving and free rolling of the disk were also studied. Copyrigh t (C) 1996 ISTVS.