Including Economy, Arco, Jaeger & Thermoil
20601 Old State Road Haubstadt, Indiana 47639
When Hercules Gas Engine-Company began producing model D engines in January 1914, their design was not brand new and unique. The engines had the general appearance and many features to be found on the model CX engines produced at Sparta, Michigan, in late 1912 and in 1913.
The 11/2, 4, 6, 8, and 10 HP size Hercules-built model D engines retained the same physical dimensions as those built at Sparta. The general appearance was also much the same. The primary differences on the four larger sizes was a change in the water hopper, a change in the fuel mixer and fuel tank spout, and a slight change to the rear of the cylinder. There was also a governor modification with the addition of a speed control screw. The decal was changed and the hopper tag was eliminated.
The 11/2 HP size was changed even less. Essentially, the only changes were the fuel mixer, the fuel spout, the hopper tag and the decal. The same block, head and other operating parts, with a few modifications, were used on the Hercules engines until 1929.
It would be later in 1914 before the Hercules-built engines would have a tag. It was first located on the engine base below the igniter before being moved to the top of the water hopper. Serial numbers began at 50,000. The model D engines had no tag.
For those hunting parts, the Economy model CX engines built at Sparta and the subsequent engines built at Evansville have a great deal of parts interchangeability.
Interestingly, the 2 HP Sparta Economy was never redesigned and remained as the model CA. Evansville production began with newly-designed 21/2 and 23/4 HP engines.
These illustrations, taken from catalogs, show the 1 HP Sparta Economy and an example typical of the 4, 6, 8, and 10 HP sizes. Without any physical changes, Hercules related these engines to 11/2, 5, 7, 9, and 12 HP by mid-1914.