Thesis (M.Eng.) - Asian Institute of Technology, 1995

A thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering.

Field experiments were conducted to optimize the performance parameters of a singleshank, tractor-mounted oscillating subsoiler. Tests were conducted at frequencies of oscillation of 3.7, 5.67, 7.58, 9.48 and 11.45 Hz; amplitudes of 18, 21, 23.5, 34, and 36.5 mm; and forward speeds of 1.85, 2.20 and 3.42 kmph at soil moisture content close to the lower plastic limit. The performance was expressed in terms of draft ratio, power ratio, energy ratio and soil loosening (in terms of percentage reduction in bulk density of the soil near the surface). It was found that the forward speed, amplitude and frequency significantly affected the draft reduction, power increase and soil loosening. Their combined effect expressed in the velocity ratio parameter (the ratio of peak tool velocity and forward speed) however has the strongest influence. The draft ratio was less at high amplitudes and decreased sharply up to a velocity ratio of 2. A maximum of 68 % reduction in draft was observed at a forward speed of 2.2 kmph, amplitude 36.5 mm and frequency 9.48 Hz. The power requirement with oscillation were higher compared to no oscillation. At maximum draft reduction the power ratio was 1. 18. Similarly, oscillation gave better degree of soil loosening than no oscillation and was greater at higher velocity ratio. At maximum draft reduction, a 34. 7 % reduction in soil qulk density was observed while for no oscillation, it was found to be 10%. The optimum performance of the subsoiler was a compromise between draft reduction and better soil loosening, and power increase and was limited by its structural strength. The machine can function effectively at a frequency range of 6 to 9 Hz. An ideally optimum combination of oscillating_ parameters is very difficult to attain under actual field conditions.