Fundamental Studies on the Shape and Action of Subsoiler (II)

Laboratory Tests of Subsoiler Models

Abstract

The power requirements (horizontal and vertical forces and torsional moment), travel speed, working depth, soil breaking and amount of soil rise on many models of subsoiler were determined in laboratory. The results were as follows:
(1) In general, the horizontal force of soil resistance to snbsoiler was about twice of downward force, and the resultant force was slightly larger than horizontal force, these three force increased with an increase in working depth.
(2) The direction of the resultant force was most influenced by cutting (oblique) angle, next was top angle and height of blade on the planetype subsoilers, but it was greatly influenced by the cutting width on the V-shaped snbsoilers. And in general, it was not almost influenced by the working depth, but increased slowly when the depth is over 20cm
(3) The elements of shape which have large effects on the horizontal and vertical forces were cutting angle and cutting width, but both forces were not almost influenced by the height of blade.
(4) The horizontal force was minimum and downward force scarcely increased when the cutting angle is about 20°, and hence in view of power requirements it was considered that this value is most desirable and the value of above 30° is undesirable.
(5) A small increase in horizontal and downward force occurred with an increase from 75mm to 125mm in height of blade.
(6) If the effect of soil surface rise or soil breaking was required, the increase of height of blade was most desirable because the horizontal force hardly increased.
(7) With an increase in cutting width of subsoiler, some increase in horizontal and downward force occurred, however the unit draft decreased.
(8) The both resistance forces scarcely increased with travel speed in the range of 0.2-0.7m/sec, and hence, high speed snbsoiling will be desirable from a view-point of the work efficiency.
(9) In clay loam, in general, both forces were greater, and soil crack was less and thicker than that in sandy loam.
(10) The amount of soil surface rise increased with an increase in cutting angle, height of blade, cutting width, and with a reduction of top angle. In general, the rise increased with working depth. However, on the subsoiler with large cutting angle or small cutting width, it was maximum at 15-20cm depth and reduced in more or less depth than that range.