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The soil response to traffic loads as affected by tire inflation pressure, track width and drawbar pull was measured. The change in soil physical properties caused by a John Deere 8870 tractor at two tire pressure settings and CATERPILLAR Challenger 65 and 75 tractors with 64 and 89 cm wide belt tracks, were measured at two load levels; no draft (tractor only) and tractor pulling a 12.5 m field cultivator. The Ohio State University Soil Physical Properties Measurement System was used to measure cone penetration resistance, air permeability, air-filled porosity, and bulk density. The results show the dual overinflated tires caused the greatest change, followed by the CATERPILLAR Challenger 65 track, then the CATERPILLAR Challenger 75 track, and finally dual correctly inflated tires caused the least effect on soil physical properties. These results were consistent at each depth. The effects of the two draft levels give the same ranking of the tractive units.

Soil response to differences in tire size and inflation pressure was measured for a JD 9600 combine with 18.4R38 dual tires, 30.5L32 single tires, 68x50.00-32 single tires at 103 and 166 kPa inflation pressure and a John Deere half-track system on two different soils (Kokomo and Crosby) near Urbana, Ohio. A loaded 42.3 m3 grain cart was included on the Kokomo soil for comparative purposes. The Ohio State Soil Physical Properties Measurement System was used to sample and measure the bulk density, air-filled porosity, air permeability and cone penetration resistance between 10 and 50 cm depths. The results for Kokomo soil show the grain cart had the greatest effect with an average decrease in total porosity of 12.90 percent, compared to 7.95%, 6.05%, 4.56%, 3.06%, and 2.04% for singles, tracks, duals, wide overinflated, and wide rated pressure tires, respectively, on the combine.

As reported by Wright and Carpenter (1) and others, the number of accidents resulting in serious injuries and deaths associated with All Terrain Vehicle (ATV) use increased dramatically during the 1980s. It was decided that a safer, more stable ATV should be and could be built. Three-wheel and four-wheel ATVs were considered. Two three-wheel ATVs and a four-wheel ATV were modified and fabricated as prototypes. While improvements of the three-wheel ATVs were realized, there were still considerable stability problems that could not be sufficiently corrected. The four-wheel prototype, denoted as RCX 250 (roll cage experimental vehicle with a 250 cc engine), demonstrated feasibility with clear improvements in safety. Analysis of the dynamics of the RCX 250 along with the description of the features and the test results are discussed.

All-Terrain Vehicles, usually called ATVs, are small motorized vehicles operating on three, four, or five low-pressure, high flotation tires that are “designed” for off-road use on a variety of terrains. As the use of these ATVs increased through the 1980's, the number of accidents resulting in serious injuries and deaths associated with A N use increased dramatically. The U.S. Consumer Product Safety Commission (CPSC) along with other surveys have estimated that one out of every 25 ATVs being used will be involved in an accident requiring professional medical attention. These problems led to the federal government working out an agreement with the major manufacturers of these vehicles. One aspect of the agreement was that there would be safety and stability standards that all ATVs would have to meet to be sold in this country.

A background review of soil compaction processes is presented and theoretical relationships among loads, pressures and soil moisture are discussed. Research directions and needs for the future are outlined. THE EFFECT OF SOIL COMPACTION, especially below normal tillage depths, is a major agricultural concern today. In general, heavy axle loads on moist soil is the primary cause of excessive compaction, But important questions remain: How heavy? How wet? Do low pressure high flotation tires help?