ABSTRACT THE effects of tire size, inflation pressure, and percent travel reduction on bulk density were determined on ourdoor bins filled with soil from the lower Ap horizon of the Cecil, Hiwassee, and Lakeland soil series. The single-wheel tire tester of the National Tillage Machinery Laboratory at Auburn, Alabama, were used in the tests. The three skidder tires used in the study were a 10 ply 18.4-34, a 12 ply 24.5-32, and a 12 ply 30.5L-32. Travel reduction (percent slip) had a greater influence on soil compaction than tire size or inflation pressure. The higher travel reduction level (30%) was associated with a decrease in soil compaction. Dynamic loads beyond about 20 kN did not cause additional increases in soil compaction.

ABSTRACT AFORTRAN computer program was developed to model the stability, traction, and production characteristics of four-wheel drive, articulated-frame, rubber-tired cable skidders. The model is heavily dependent on the equations developed by Wismer and Luth (1972). Relative production rates can be estimated as a function of skidder design, tire size, trail slope, soil cone index, and load characteristics.

ABSTRACT THE performance of three different sizes of log-skidder tires was compared at two travel reduction and two inflation pressure levels. Results indicated that when log-skidder tires are operated on dry soil conditions there is little effect on performance due to tire size. Inflation pressure should be set at the minimum recommended level for a particular tire load.

ABSTRACT TESTS on selected pneumatic tractor tires for vari-ous soil conditions show that dynamic load, as well as travel reduction, plays an important role in deter-mining tractive performance. The data indicate that in many field conditions tractive efficiency could be improved by selecting an appropriate dynamic load for a particular soil condition.