Written by Larry Gay
The early farm tractors were powered by engines that burned gasoline. As automobiles became popular, the price of gasoline increased and the tractor manufacturers redesigned their engines to burn the lower-cost kerosene. By the late 1920s, distillate began to replace kerosene as the low-cost fuel for tractors. Gasoline was required to start the kerosene and distillate engines. The first diesel engines in farm wheel tractors appeared in the mid-1930s.
In 1941, Minneapolis-Moline introduced a liquefied petroleum gas (LP-gas) engine for its model U series tractors. The 4-cylinder, 283-cubic-inch LP-gas engine with a rated speed of 1,275 rpm was built with the same 4.25-inch bore and 5.00-inch stroke as the gasoline engine. However, the compression ration was 6.8 to 1, instead of 5.4 to 1 for the gasoline engine. The Minneapolis-Moline engines were unique with the cylinders and heads cast in pairs and attached to the crankcase by studs.
The Minneapolis-Moline U was the company’s largest row-crop tractor in 1941 and was rated as a 3-4 plow tractor. It could be equipped with dual front wheels or a single front wheel. The U was also available as a standard-tread tractor. The transmission provided five forward speeds. The U developed 45.3 belt horsepower with its gasoline engine when tested at Nebraska in 1939 and 48.8 belt horsepower with its LP-gas engine in 1948. Both tests were corrected for temperature and barometric pressure.
Other tractor manufacturers soon followed Minneapolis-Moline’s lead and began to offer LP-gas engines as an option. By the late 1950s and early 1960s, most tractor builders offered a choice of gasoline, diesel, or LP-gas engines. The Minneapolis-Moline G955 and G1355 were the last new models of MM tractors, being introduced in 1972, and they were available with a choice of 6-cylinder LP-gas or diesel engines.
Larry Gay is the author of four farm tractor books published by the Americn Society of Agricultural and Biological Engineers. These books may be obtained from ASABE at 800-695-2723 or www.asabe.org, click publications and then click history books.