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The influence of liquid ballast on tractor tire stiffness was determined from static tests that measured tire load, deflection, and inflation pressure. The tire load-deflection data were fitted with a regression model. The model was differentiated to determine the stiffness of the tire at various combinations of deflection, inflation pressure, and liquid fill. Stiffness at the rated deflection was substantially higher when liquid ballast was used. The increase in stiffness was much less when inflation pressure was reduced to offset the hydrostatic head produced by the liquid fill. The remaining increase in stiffness was due to the change in volume inside the tire during deflection and the smaller volume of compressible fluid in the liquid-filled tire. This study indicates that liquid ballast has a negligible influence on static tire stiffness, if the inflation pressure is determined on a loaded tire and is properly adjusted to compensate for hydrostatic head.

Agricultural irrigation pumps are frequently powered by common automobile or tractor spark-ignition (SI) engines burning natural gas. Typically, these engines operate at part-throttle and at constant speed and load. Investigated was the fuel consumption reduction that occurs with application of the more-complete-expansion cycle. Using a Chevrolet 5.74 liter (350 cubic inch) displacement engine for calculation purposes, fuel consumption rates are predicted as 12 to 16% less than a conventional engine (reference case). Economic analysis reveals that with irrigation pumps operating from 1000 to 2000 hr/year, the cost of modification is recovered by fuel savings (SO.97 per kg of natural gas) in one to two years.

The primary problems associated with straight soybean oil as a fuel in a compression ignition engine are due to high fuel viscosity. Transesterification provides a significant reduction in viscosity, thereby enhancing the physical properties of the fuel to improve engine performance. Methyl, ethyl, and butyl esters of soybean oil revealed fuel properties similar to diesel fuel. Engine wear, deposits, performance, and emissions are reported for each of the ester fuel's and reference diesel fuel's 200-hour engine tests. Analysis of lubricating oil samples are also presented as well as complete fuel injection system test results.

In 1976 an agricultural production energy conservation project was initiated by Kansas State University and the University of Nebraska. The main objective of the program was to develop a model fuel conservation program. This paper is a report of the results of the project relating to field operations. Results indicated that farmers are interested in saving fuel. The farmers who cooperated in collecting fuel consumption data indicated that fuel record keeping made them much more aware of energy costs for individual operations. Practice of currently available energy conservation technology results in significant energy savings. The field demonstrations used were highly successful in showing farmers exactly how to accomplish several conservation techniques. Industry can have a very important part in solving the energy-food production problem. Increased emphasis on engine efficiency is needed.