A Chapter in Diesel History

Special thanks to Lyle Cummins, Mike Murphy and Randy Watts

In past Vintage Smoke we’ve talked about the vaporizing fuel oil engines of the 1895-1930 era and how they related to, and competed with, the engines we now know as “diesels.” One early engine that straddles the gap between a diesel and a vaporizing oil engine is the Hvid (pronounced “Veed”) engine, sometimes also called a Brons engine. It’s an oddball four-stroke “almost-a-diesel” design that took a chunk of the US oil engine market for about 15 years.

Recapping The Vaporizing Oil Engine

There were many types of vaporizing oil engines, commonly known as “hot head,” “hot bulb” or “hot tube” engines, built from the 1890s into the 1940s. Almost all were 2-strokes. They were “compression ignition” in a sense, but achieved ignition with only 1/3 the compression pressure of a diesel. They could ignite the heavy fuel only because of a hot vaporizing chamber, or a tube that extended into the combustion chamber. The vaporizing chamber had to be very hot for starting and warmup, so external heat (usually from a kerosene torch) was needed to make that external chamber almost cherry red to vaporize the fuel for easy ignition. Once hot, the chamber was maintained at the correct vaporizing temperature by the heat of combustion. If the engine wasn’t run with enough load, sometimes the engine could not maintain the heat needed to sustain combustion. It was an inefficient system but allowed fuel oil engines to be much smaller, less complex, considerably less expensive than true diesels and able to run on a variety of fuel types and grades.

The Fuel Injection Gap

The biggest technical obstacle to practical diesels in the early days was the fuel injection system. Rudolph Diesel’s original designs used air blast injection (1000 psi compressed air behind fuel oil) to inject and atomize fuel. It worked better than you might think, though the ancillary equipment needed was considerable. It took a while before Robert Bosch and other industry pioneers perfected the first mechanical injection systems that could finely atomize liquid fuel and inject it into a pressurized combustion chamber just ahead of the hottest point of the compression stroke. The first solid injections were found on vaporizing oil engines but they were very low pressure systems . They worked because two-stroke oil engines, often using ports rather than valves, had low compression ratios and very early injection events, needed to give the fuel time to vaporize.

Brons and Hvid

It started with a Dutchman, Jan Brons (1865-1954), who was the engineering brains behind a new engine company in Holland. The company started in 1900 and soon began working towards a diesel. The Diesel patent was not in force in Holland so Brons developed a prototype four-stroke engine that used a different form of air blast injection. While testing the prototype, the air compressor failed but to Jan’s amazement, the engine continued to run. On the suction part of the stroke, enough air and fuel were drawn into the small injector cup to be vaporized by heat and then blown into the main combustion chamber via small orifices by expansion where full combustion took place.

By 1904, Brons had figured out how to make his accident perform better and patented an optimized version. He quickly filed patents in Germany and Britain and was soon making engines. Along the way a new company was formed, N.V Appingedammer Bronsmorerenfabrick, in Appingedam, Holland. One of the founding fathers of diesel, Gasmotoren-Fabrik Deutz (now known as Deutz AG) even bought a license and built Brons engines into 1926. The Brons company stayed in business until 2004, mostly building marine engines. The last Brons prechamber engine was built in 1946. Enter Rasmus Martin Hvid (1883-1950).

Hvid was Danish by birth but had become a naturalized US citizen. A trained engineer, Hvid was working for the Advanced Thresher and Rumley Companies when he had the bright idea to patent an engine design that closely resembled the Bros engine in Europe, and sell licenses here in the USA. He filed for a US patent in February of 1912 (granted in 1915) and there were subtle differences enough that it passed engineering review for the patent. Though Hvid began selling his own licenses in 1913, it turned out his variation was not as good as the Brons so he quietly acquired a Brons license in 1914, which probably also avoided legal issues.

The Hvid engine was well marketed and soon acquired scores of licensees here in the States and many overseas. These included some bigger names like Hercules and Bates & Edmonds, as well as a new company, The Cummins Machine Works of Columbus, Indiana. Yeah, that Cummins.

Clessie Cummins’ Folly

The founder and first engineer of what became the legendary Cummins Inc. was fascinated by diesel engines and while running his small machine works out of a garage, he had dreams to design and build them. Cummins had plenty of ideas and drive, but the fledgling company didn’t have the capitol to develop a unique design. When he learned of the availability of Hvid licenses, he saw that as a jumpstart towards an engine company. His very astute and business-minded partner, W.G. Irwin, released enough money to buy a Hvid license in January 1919 and found investors to help the company tool-up to produce Hvid engines. The first engine, built more or less to the same design as the Hercules Hvid, was going in a couple of months. They marketed engines under the Cummins nameplate but sales were not brisk. Along comes Sears, Roebuck & Co.

Hercules was building Hvid-licensed engines for Sears under the Thermoil brand and demand had outstripped Hercules production capacity. Cummins-built Hvids had attracted some positive attention because they made as much power as the Hercules Thermoil with about 16 percent less displacement. When Cummins was approached as an additional supplier to Sears for up to 4,500 Thermoil engines, Cummins jumped at the chance, not knowing he was jumping into a pot of boiling oil.

Cummins was contracted to develop and build lower-power, smaller displacement engines than they already had built. He soon discovered problems with the smaller engines that had not been present with the larger. Ever the perfectionist, Clessie spent a lot of time and effort to solve them but as a result, production rates fell way below what Sears would accept. At the same time, a very liberal Sears guarantee allowed buyers to return the engine within 30 days at no cost if they weren’t, “satisfied in any way.” Crafty farmers were buying engines at harvest time, using them hard for 30 days powering threshing machines and returning them. Free power for a month! In fact, that became somewhat a cottage industry until Sears finally caught on. Per the contract with Sears, most of the returned engines came back to Cummins, many of them well used, and Cummins had to eat the cost. By 1922, Cummins wanted out of the Sears contract and that happened in 1923 after making approximately 3,000 Hvid Thermoil engines. It took a little longer to get out of the Hvid licensing agreement but Cummins went on to bigger and better things.

The Quirky Hvid

The Hvid had efficiency advantages over a vaporizing oil engine when viewed in “The Perfect World.” The weakest part of the Hvid system was a sensitivity to fuel types. Many Hvids were set up to run Kerosene, which was one of the few somewhat standardized and clean fuels of the time. Though advertised as being able to use a variety of fuels, a Hvid actually required some tuning to go from one grade or type of fuel to another to start and run optimally. That was often beyond the capabilities or concerns of small operators who added whatever fuel was handy and then bitterly complained when the engine didn’t run well, or at all.

The high compression ratios of the Hvid (14-16:1)made them a bit harder to start by hand than the low compression gasoline and oil engines but they could start a lower temperatures and did not require external heat beyond filling the cooling water hopper with hot water. Once started, and if correctly tuned for the fuel, the Hvid was reliable and economical along the lines of a true diesel. Read more about how they worked in the nearby sidebar.

With the rapid advance of diesel technology after World War I, it didn’t take long for the engine market to bypass Hvid engines. By 1930, the era of the Hvid was over in the USA. Vaporizing oil engines continued a bit longer because they were less quirky and less expensive. The “true” diesel ultimately became king.

While many variances existed between the companies building Brons or Hvid engines, the operating principles were the same. Shown here is a Hercules/Thermoil. The Hvid was a four-stroke engine and at  500-600 psi maximum firing pressure, it was right in there with diesels of the day. The actual firing pressure varied according to the fuel used. When built for kerosene, the firing pressure was in the 350-400 psi realm because kerosene ignited more easily and hit hard when it did. With heavier fuel oils that burned more slowly, firing pressure was up there near the maximum. The compression ratio was altered in some engines by shimming the connecting rod and change the position of the piston to increase or decrease combustion chamber volume. Also, the size of the orifices in the fuel cup (9) had a similar effect, with larger orifices better for heavy fuel and smaller orifices better for lighter fuel, such as Kerosene. The “injection” system used little more than gravity and intake suction on the intake stroke to feed fuel. The fuel was gravity fed from a tank to the fuel reservoir (1). The amount of fuel delivered was regulated by the fuel metering pin (2), the position of which was regulated by the governor via the governor rod (3). Fine adjustment of rpm could be made using the speed control wheel (5) which adjusted the highest position of the metering rod. The metered fuel and a little air filled in behind the fuel inlet valve (6) and that valve was synchronized to open during the intake stroke. The fuel valve was operated by the fuel valve rod (7). The fuel valve opened into the fuel cup (8) and was timed to close partway into the compression stroke, leaving fuel in the fuel cup. Heat in the combustion chamber and the rising heat of compression would vaporize the lighter elements in the fuel in the fuel cup and they expanded to blow the heavier parts of the fuel out several orifices in the fuel cup (9) and heat of compression ignite the rest of the charge in the main combustion chamber (10). The intake (11) and exhaust (12) valves operated as most other engines, though some Hvids used atmospheric intake valves.

Sources

Diesel’s Engine by C. Lyle Cummins Octane Press
https://octanepress.com/

Coolspring Power Museum
http://www.coolspringpowermuseum.org/