On the Maximum Drawbar Pull of Tractors concerning with the Type of Soil

Abstract

The pulling performance of the tractors, which are well adapted to heavy duties, as soil-improvement work and reclamation work etc., should be determined with not only the drawbar horse power but the maximum drawbar pull and the increasing rate of slip causing by the draft.
This paper contains the maximum drawbar pulls and the maximum specific drawbar pulls (The maximum drawbar pull/Total weights of tractor including fuel, oil, water and operater) characterized to the type of tractor-crawler, semi-crawler, and wheel-which were investigated in the different types of soils-dry or wet heavy clay soil, clay-loam and volcanic light sandy loam or gravelly soil. i. e.
1. If the type of tractor and the method of hitching are both similar, the max. specific drawbar pulls are approximately constant value concerning with the type of soil. (vid. Table 3)
2. The value of the max. specific drawbar pull may be higher in heavy clay soil, lower in volcanic soils, and medium in clay-loam.
3. In heavy clay soil, increasing the moisture content, decreases the max. specific drawbar pull. But just opposite in volcanic soils.
4. Where the moisture content is not so much in heavy clay soils, the max. specific drawbar pull of crawler tractor is a little higher than wheel tractor. But in volcanic soils, the difference of these values is evidently large amount.
5. If wheel tractors are set the wheels on the land for subsoil-plowing, where the furrow walls may collapse easily, the max. specific drawbar pull decreases evidently, in such field it is almost impossible to increase the max. drawbar pull by setting the wheels in the furrow-sole.