Hercules Engine News

Including Economy, Arco, Jaeger & Thermoil

6 HP model U Thermoil Engine

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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.

Reportedly, development of the model U in 1?, 3, 6 and 8 HP was going on as early as 1915, but production didn't begin on the 6 and 8 until 1919 when the new Hercules foundry became operational. Other brands known that were very similar to the 6 and 8 HP model Thermoil included Cummins model C, PENMAC, Brantford, Hoag, Johnny, Victory and perhaps others.

The model U was last offered in the spring 1921 Sears catalog. Serial number data collected to date indicates that there were approximately 3000 of these model U engines built under the Thermoil brand. It is likely that another 1000 Thermoil 'look alike' engines were produced as other brands. Today, at least 26 are known to still exist.

The tag states that these engines were built under license from the R. M. Hvid Engineering Company of Chicago, Illinois. In some literature it mentions Robert M. Hvid. Three patents issued in 1915 were to Rasmas M. Hvid of R. M. Hvid Engineering. Perhaps Robert and Rasmas are one and the same with the name being changed when he became a naturalized U. S. citizen. Remember, Hvid in the native Danish country is pronounced 'Vied'.

In the fall 1921 Sears catalog, slightly altered Thermoil engines appear, but that's another story.

When the 6 and 8 HP model U engines made their debut on the market, there were some interesting related events occurring at Columbus, Indiana, that would lead to the organization of the Cummins Engine Company. That will be 'The Cummins Connection' story.