Issue #31: Power Units

Oliver Power Units

By Sherry

Power units have been around longer than the tractor but never quite gained the same popularity in collecting, until recently. Hart-Parr’s first creation was a stationary engine back in 1898. Oliver continued to build power units until 1960 using the same engines of the popular series of tractor of that time.

Hart-Parr’s early engines were all used as a power unit of some type. When tractor production took over, they discontinued typical power unit production. In the 1920’s they once again offered stationary engines using the same engine at the tractor. These were complete with a radiator, clutch, base and other accessories. They also worked with Buhl in 1928-29 to provide engines for some of their air compressors and winches. The top radiator tank was even cast with the Buhl name in it. These were built in very limited quantities.

When Oliver united with Waukesha on the Oliver 60, it appears that they also tinkered with the idea of putting that engine in a power unit. These artist renditions were found at the Waukesha Engine Historical Society Archives and are dated 1945.

In September 1950, Oliver finally introduced a full series of power units to correspond with the tractor models. This line-up consisted of the 166, 177 and 188 available in both gas and diesel. The dealer service bulletin indicates that LP and natural gas models will be available soon. Although serial number lists indicate that the 199 was also available in 1950, the dealer bulletin makes no mention of it.

While these engines were based on the tractor models, they were not identical. Power units had different applications and were modified to fit such. A tractor engine runs under full load only 50% of the time while the power unit runs full load 80% of the time.

The gas engines used in the 1950-1954 power units had an increased bore over the tractors. Diesel power units had the same bore as the diesel tractors. When the 199 power units were released, both tractors and power units had the same bore regardless of their gas or diesel designation. All power unit models had increased RPMs over the tractors.

To read the entire story about the full line of Oliver Power Units, subscribe to Oliver Heritage or Order back issue #31.