The drawbar pull of skidders

Abstract

The running resistance and the adhesion force of skidders were investigated in relation to the sinkage from BEKKER's resistance theory. 1) The running resistance of hillside skidders whose center of gravity location and wheel-load distribution can be changed is smaller than that of common skidders when climbing slopes because of the sinkage caused by the difference of load distribution between the up-side wheels and the down-side ones. For example, the running resistance of a common small-sized skidder to sinkage is 10% larger than that of the same-sized hillside skidder when climbing. 2) The increase of the adhesion force is slower than the increase of the running resistance. Therefore, the drawbar pull arising from the difference between the adhesion force and the running resistance turns out to be a convex curve with a maximum value. 3) The running resistance of a hillside skidder will be 14% smaller than that of a common skidder, and the drawbar pull of the hillside skidder will be 4.6 % larger by a calculation based on the application of UFFELMANN'S sinkage equation. 4) It was recognized from our experiments that the difference of drawbar pull between hillside skidder and a common skidder was nearly equal to the above theoretical values on the first pass, and on forest land which skidders had traversed many times, the drawbar pull of the hillside skidder was approximately twice that of the common skidder.