The Original Cummins Diesels


| November/December 1980



Sectional view of Cummins oil engine

Courtesy of Ken Davidson, 60110, Cummins Engine Co., Inc., Columbus, Indiana 47201.

Ken Davidson

40646, Cummins Engine Company, Inc., 1000 Fifth Street, Columbus, Indiana 47201.

This article is reprinted from Cummins Clippings, magazine of Cummins Engine Company, Inc., Columbus, Indiana. Permission to reprint has been given by Ken Davidson, Editor. The article was brought in by Aden L. Hawbaker, 8586 Talhelm Road, Chambersburg, PA 17201, owner of a restored Thermoil engine.

The first Cummins diesels were known as Hvid type oil engines. They were built under a license granted by a Robert M. Hvid who owned the U.S. patents for the fuel and combustion system. During the years 1919 through 1922, Cummins built 1?, 3, 6 and 8 horsepower Hvid engines. All were single, horizontal-cylinder type.

Except for size, these engines were of the same design. The details are shown on the cross section that appears with this article.

The Cummins Hvid engines were compression ignition engines. We call them 'diesels' today. They had a precombustion chamber into which fuel was fed by gravity through metering valves controlled by the governor. The fuel was fed into the cup during the intake stroke. During compression, the fuel would heat up and partially vaporize. Then, when it reached ignition temperature, the vapor would explode and drive the main fuel charge with the cylinder.

Cummins never was able to resolve several problems with this fuel system. First, the ignition timing varied with fuel quality, air temperature, and other factors. Clessie Cummins' first diesel invention was a means to mechanically time the ignition. By lengthening the fuel valve, he sealed off the orifices between the cup and the cylinder until the proper time for ignition. This invention enabled Cummins to get six horsepower from an engine that was originally designed for five horsepower.