Soil pressure and pulling behavior of standard and half-track tractor chassis concepts

The investigation deals with the specific behavior of tire and new half-track based tractor chassis concepts under pull-condition, where horizontal and vertical forces occur between tractor and implement. These forces lead to a change of the front- and rear axle loads, compared to non-pull condition. The pulling forces lead to a pitch effects of the tractor and can also result in a pitch effect of the track system, depending on the design of the track system. This effect can lead to an uneven contact pressure in the belt-soil contact. To evaluate the pitch effect and the risk of soil compaction, measurements of the ground pressure with “Bolling Sensors” have been carried out to indicate the effect of the pulling forces to the tractor chassis and the soil pressure. The investigation of the ground pressures have been done in a comparison of a standard tractor Axion 960 and two half-track tractors Axion 960 with the CLAAS TerraTrac and CASE-IH Magnum 380 Rowtrac with triangle tracks under pulling conditions with specific ballasting configurations. The investigation of the pulling behavior of the tractors have been executed as a comparison of two Axion 960 tractors, one in standard tire version and the other as half-track version. Both tractors have the same configuration of engine-power and transmission configuration with CVT transmission. The results are, that the CLAAS TerraTrac track system features a significant reduced soil pressure in no-pull and also in pull-condition in comparison to standard tires. Also in comparison to a triangle track system with positive drive principle the soil pressure of the CLAAS TerraTrac system with the suspension is much lower. The comparison of pulling performance shows an improved pulling potential at speeds < 10kph of the TerraTrac system compared to the tired tractor. At higher speeds, the tire-soil contact is not the limiting factor and so wheeled and track-typed tractor show a similar pulling performance.