1) Experiment was carried out on sandy loam in soil bin of Hokkaido University to know the effect of implement mast height on traction of farm tractor.
2) The experiment was based on the fact that when the mast height i. e. geometrical location of virtual hitch point was changed and the weight transfered to the rear wheels of the tractor that was doing plowing operation under constant load increased, the travel reduction of the rear wheels decreased.
3) It was found that the specific resistance of test plows (18″×1, 14″×2, 14″×3) was decreased according to the increase of working width when the depth was the same. The result obtained above resembled the tendeney of Japanese plow.
4) As working depth of each plow increased, draft increased in second order. But the changes of horizizontal forces in top link and lower links were contrary to each other. The balance of forces that each link was loaded changed considerably depending on mast height.
5) As draft increased (from 18″×1 to 14″×3 plow) travel reduction showed significant difference by changing mast height. The reason was because, as mentioned above, at 4), the balance of forces (that each link was loaded) was changed and the weight transfered to the rear wheels increased.
6) Judging proper mast height for the test tractor based on the idea of practical max, pull which was defined by 20% travel reduction, mast height was desired to be 65cm.
7) Mast height is generally standardized to be ranged from 46 to 51cm. But from the view point of effective usage of weight transfer, it was recognized that the virtual hitch point should be placed at the center of gravity of tractor.
