Tractive performance of the tractor used in forestry works (II)

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Other Title
  • 林業用トラクタのけん引性能に関する研究 (II)
  • 林業用トラクタのけん引性能に関する研究-2-小形車輪のけん引特性
  • リンギョウヨウ トラクタ ノ ケンイン セイノウ ニカンスルケンキュウ 2 コ
  • 小形車輪のけん引特性
  • Experimental studies on the tractive properties of a small-sized wheel

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Description

In spite of the wide use of the wheel-type tractor (articulated type) in forestry, the fundamental properties of its traction do not always seem to be satisfactorily clear. Therefore the author carried out some basic experiments on tractive effort in his laboratory with a small-sized wheel under two different ground conditions (deformable soil and humus surface). The apparatus with which the dynamic relations between a tire and soil can be easily measured is shown in Fig. 1. The following results were obtained from these experiments: (1) Ground contact pressure of the tire driven on hard surface soil, such as concrete pavement, is directly affected by the inflation pressure of the tire. On deformable soil, its value is mainly affected by hardness of soil. (2) From the experimental values of rolling resistance of the tire driven on deformable soils it is obvious that the coefficient of rolling resistance is almost proportional to the square root of the sinkage of the tire. (3) It is considered that adhesion of the test tire with short lugs is produced, not by shearing resistance of soil, but by the friction between the tire and soil. During the entire experiment, the coefficient of adhesion remained in the low range of 0.5_??_0.6. (4) The coefficient of traction can be expressed as difference between adhesion and rolling resistance. This coefficient, which is not only directly affected by the hardness of soil, but independent of the inflation pressure, decreases against the increase of axial load of the wheel. This relation is shown in Fig. 14, in which three coefficients can be compared. (5) The values of coefficient of rolling resistance and adhesion of the test tire driven on the surface covered with raw humus decrease from 10 to 30 per cent, and the coefficient of traction decreases from 10 to 40 per cent as compared with that on soil surface without raw humus.

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