Experimental Studies on the Analysis of a Travel Reduction Ratio
1970 Volume 31 Issue 4 Pages 287-291,302
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1970 Volume 31 Issue 4 Pages 287-291,302
In this paper the authors described experimental studies on the relation of dynamics between the soil and the tire tread surface to the travel reduction, and a special emphasis was laid on the definition of a travel reduction ratio.
We provided a soil bin which was filled up with soft soil to make slip of the drive wheel. The tractor was moved on the bin, under varying conditions of the tire inflation, the wheel weight, and the pulling load, and the kinetic locus of the wheel was photographed. At the same time the pulling load and the strain of the deformed tire under tread were measured.
The conclusions were as follows:
(1) While the tractor travelled on the surface of such soft soil into which the lug surface of the tire sank, a given point of the lug surface followed a kinetic locus of looped trochoid curve. The shape of the spiral in the curve signified the rate of travel reduction. The travel reduction ratio has been usually expressed by the rate of reduction in the travelling distance with loaded state as compared with that at no load.
If the firm clod which was compressed between the lug was disconnected from the soil surface, was broken, and caused the wheel to slip, the term “slippage” was more appropriate than the term “travel reduction ratio” to express the situation.
(2) An unexpected low value (approximately 4.2 to 7.4 per cent) of travel reduction ratio was obtained when the clod which was compressed between the lug began to crack under the influence of pulling load. The travel reduction ratio at the time the lug clod was disconnected from the soil surface might agree approximately with that at the hign tractive efficiency. It seems that the tire began to slip at the moment of disconnection of the lug clod.
(3) While the lug penetrated into the soil and again emerged, the tire under tread was largely deformed. in comprssion. After the strain of comression reached the maximum value, this state was kept even when the pulling load was increaced. It was observed that the slip started when the under tread reached the maximum strain.
