From 1919-1922, Cummins manufactured four sizes (1.5, 3, 6, and 8HP) of the same engine, which we call the HVID. The entire engine design was bought from Hercules, so no Cummins design went into the initial engines, but Clessie did improve the design along the way (see below).
We call it the HVID because the fuel system was patented and licensed by Rasmus Martin Hvid. The HVID fuel system was a derivative of the Brons fuel system and both are essentially the same other than the cup/nozzle design. Neither Brons nor HVID systems were true diesels. Diesel is specifically the high-pressure injection of the fuel into the power cylinder, where high-temperature compressed air ignites the fuel. Brons and HVID used no fuel pressure. Gravity fed fuel the injector, then the vacuum of the intake stroke pulled the fuel down into the injector cup. The cup acts as a prechamber, and as the piston compressed the air on the up stroke, the air would enter the cup, atomize and heat the fuel, and initial combustion would occur in the cup. The explosion forced the rest of the fuel out into the power cylinder, where it would finish combustion.
Thinking through this always blows my mind. The design the Brons/HVID system means the fuel ignites whenever flashpoint is reached, making timing a function of fuel quality, compression ratio, and ambient temperature – which adds up to a lot of variation. Our engines came with a three piece connecting rod with shims that allowed you to lengthen the rod, thus increasing compression ratio and allowing you to time the engine. Kerosene typically required no shims (lowest compression), but other oils like whale oil required quite a few shims.
Clessie quickly picked up on the shortcomings of the system and set out to address what he could. His first patent created the first fuel return line, allowing any air or fuel that had entered the injector and leaked past the seals to escape and freely return to the tank. His next patent created the first water-cooled injector, which reduced timing variation due to ambient temps. By the end of his life, Clessie would have 33 patents to his credit.
In 1921, Clessie designed his first engine, and upright/vertical piston engine with 1 or 2 cylinder configuration and the HVID fuel system. This engine was designed specifically for boats and was tested on Clessie’s personal boat the ‘CECO 1’ before being put into production. According to Clessie, the engine performance died off every 3-5hrs
due to injector nozzle coking, but since the injector was easy to remove and clean the boat owners were ok with this task. What they weren’t ok with was the crankshaft counterweights coming off. Word quickly spread and our engines were out.
With this, Clessie knew he needed an entirely new engine and fuel system. We ceased all engine production in 1923, and sold Clessie’s HVID patents back to Mr. Hvid in exchange for ending the contract. He hired Hans Knudsen away from the St. Mary’s Engine Co and made him our first chief engineer (great hire!). Together they designed the Model F, our first wholly designed engine which started production in May 1924.
"When Diesel Isn't a Diesel", Paul Harvey, 2010: http://coolspringpowermuseum.org/Publications/Flywheel/Flywheel_201210.htm
"My Days with Diesel", Clessie Cummins, 1967
US Patent 1,557,143: https://patents.google.com/patent/US1557143?oq=1557143
Artist rendering of a 3HP Cummins HVID
6 (or 8?) HP Cummins HVID with a gear driven Barnes Mfg Co water pump
Our recently repainted 3HP HVID engine
Clessie's boat, CECO 1, being put into the Ohio river at Madison, Indiana. Powered by a Cummins diesel
1921 Advertisement for the upright Cummins HVID engine
One of the two known surviving vertical Cummins HVID engines
4cylinder Model F - only 4cyl known to exist. This particular engine was built for Northwest Mfg to repower a steam shovel