Hercules Engine News

Including Economy, Arco, Jaeger & Thermoil

| March/April 1993

6 HP model U Thermoil Engine

20601 Old State Road Haubstadt, Indiana 47639.

The hastily designed model T Thermoil engines disappeared from the Sears catalogs after 1917. A year and a half later in the fall of 1919 catalog, there appeared completely redesigned Thermoil brand engines; however, they were still covered by the same patents. These were the model U.

They were heavier and obviously more sturdily built. There were more bolts holding the cylinder to the base and they had four bolt main bearing caps. They no longer contained castings and parts used in the production of Hercules and Economy gas engines. This solved the breakage problems, but the injector and fuel regulation problems remained. The sizes offered were 6 and 8 HP, selling for $199 and $249, plus shipping. Shipping weights were 1250 and 1650 pounds. The actual weights were about 200 pounds less per engine. They were also offered as portable engines. They used the typical Hercules/Economy drop frame cart, available for an extra $52.25. Another $45 bought the whole tilting table saw rig. The clipping (top right) illustrates the liberal terms offered.

They were said to run on cheap fuels including kerosene, fuel oil, crude oil, distillate or any other similar fuel. They could be run at about 1/3 of the fuel cost of a comparable size gasoline engine. Other promotional features were that they had no magneto, no ignitor, no carburetor, no battery and no coil or wires.

Another change on the model U engines were the addition of shims that could be taken out or added between the connecting rod and the crankshaft bearing. This allowed adjustment of compression to suit the particular fuel being used and to compensate for valve head wear and connecting rod bearing wear; however, no special instructions in this regard have been found. There was a special bulletin, #7186 T, mentioned as being available from Sears, but so far, none has turned up.

The 6 HP model U Thermoil #8754 shown in the accompanying photographs belongs to yours truly. It was located in the fall of 1973 when fly wheels were seen sticking up out of the weeds along a gravel road in the rural southern Indiana hills. It was brought home December 26, 1973.