VINTAGE SMOKE
1923 FAIRBANKS-MORSE Y-V SEMI-DIESEL
1923 FAIRBANKS-MORSE Y-V SEMI-DIESEL
The diesel engine didn’t just appear from thin air—it was an evolution of technology. In the years immediately following Rudolph Diesel’s 1895 patent, much of that evolution was dictated by those patents in Europe and the United States. Back then, engines that ran on heavy fuel oils were called “oil engines,” and it would be a few years until Diesel went from a capitalized proper noun to a lowercase common noun used to describe the compression-ignition engine.
Another category of oil engine coexisted with— but predated—the diesel. Called a “surface ignition” engine, it was a low-compression oil engine that used the heat of compression for ignition. It could only sustain compression ignition when the combustion chamber was really hot and there were hot spots to vaporize the fuel that was injected at very low pressure. The surface ignition engines were also divided into several categories and by names that described their ignition method.
SEMI-DIESEL
The most common was the “hot-bulb,” where the combustion chamber was external and bolted to the top of the head like a projecting globe with a chimney over it. The exterior of the globe would be heated by a kerosene torch for starting, but after running a while, it could retain enough heat to sustain ignition. Sometimes the exhaust system was routed around the globe to apply more heat. There were also “hottube,” “hot-cylinder,” and “hot-head” combustion chambers that were a different means to the same end—namely vaporizing the fuel enough so it could be ignited at lower temperatures (700F or less).
Englishman Herbert Akroyd-stuart designed the first commercially available hot bulb engine and the manufacturer, Richard Hornsby and Sons, added a primitive “jerk-pump” fuel injection system, making it the first mass-produced fuel injected engine. These hot-bulb engines predated Dr. Diesel by a few years, but Diesel’s upgrade to the oil engine was a drastic increase in compression that could sustain ignition by heat of compression alone. The big problem Diesel faced was injecting fuel into the highly pressurized combustion chamber, and the jerk-pumps used by the hot-bulb engines couldn’t do it—at least initially.
Diesel’s oil engine wasn’t suited to every engine application. Plus, it was expensive to build and buy. Companies building Diesel engines also had to pay a licensing fee. All this made the low compression oil engine an attractive alternative, even if it was less efficient and economical than the Diesel. When the Diesel patent expired in the U.S. in July 1913, many existing engine builders began the transition into lowercase diesels. By then the non-diesel oil engine had become common and practical, and it took a while for the diesel to replace them.
SEMI-DIESEL
Oil engines were divided into three general categories: low compression, medium compression and high compression (later known as the Diesel). In reviewing period literature, we can further define that as low compression engines having compression pressures of about 70 to 150 psi (approximately 5:1 to 8:1 CR). Medium compression engines were between 150 and 250 psi (up to a 13:1 CR, or so). Nearing 500 psi and over was considered high compression. The old manuals say to be a “true” diesel, the compression pressure mark was 500 psi. As use of “diesel” became common to describe the high compression oil engine, the medium compression engines became “semi-diesels.” Low compression oil engines technically aren’t semi-diesels using that old definition, but over the years they have been lumped into that category.
Fairbanks-morse (F-M) was already an old manufacturing company when they designed and began building internal combustion engines in 1893. Their gasoline engines quickly established an enviable reputation, and their existing distribution system and dealer network enabled them to hit the ground running in the engine market. By 1912, they also had an oil engine of their own, and it went on the market in 1913 as the Type Y, Style H (for “Horizontal”). It was a variation of a hot-bulb, low-compression oil engine that was built through 1914.
F-M moved toward a true diesel by updating their Type Y, Style H line in 1915 with an improved combustion chamber called a “hothead.” Some engines also had the injector moved from the side to the top of the combustion chamber. This evolution retained some aspects of the hot-bulb setup, but with an increase in compression (to about 150 psi), the engine could better sustain ignition via compression. It was an early variation of the what we now call indirect injection, with fuel being injected into a separate chamber connected to a smaller chamber above the piston. Commonly called the Y-H, it was a single cylinder horizontal engine that was eventually offered in a range of 10, 15, 20 and 25 horsepower with an assortment of bores and strokes.
The tricky part of low and medium compression oil engines was start up. They didn’t generate enough compression to self-ignite the oil until the combustion chamber was very hot. “Firing up” these early engines required real fire! With hot-bulb engines, a kerosene torch was use to heat the outside of the bulb before the engine was spun over. The hot-head had a hollow stud that protruded outside the combustion chamber and was heated via the torch. On a moderately temperate day, getting enough heat into the engine could take 10 minutes. On a cold day it took even longer. Once the engine was well warmed up, the external heat could be removed. Some of the surface ignition engines that remained on the market a long while were updated with electric glow plugs to replace the fire.
The Type Y engines expanded to a multi-cylinder range in 1914 with the Type Y, Style V (for “Vertical,” commonly called the Y-V). It was offered in two bore and stroke dimensions: 12 x 15 inches and 14 x 17 inches. Compression was about 265 psi and they used a hot-head design. The smaller bore engines were offered in one- to three-cylinders inline, making 37.5 hp per cylinder. The larger engine was built with one- to four-cylinders inline making 50 horsepower per cylinder at 257 rpm. Continual improvements in their nearly 10 years of production brought those numbers up a bit.
The late Y-H and Y-V engines were true semi-diesels, but in 1924 F-M debuted their first full diesel: the Y-VA. It was also offered in small and large displacements, but a six cylinder was added to the large displacement line. Though similar in architecture to the Y-V, the Y-VA had many improvements—most notably a increase in compression to about 500 psi. Maximum power stayed largely the same as the Y-V, but by increasing the rpms up to 75 horsepower per cylinder was offered. In 1925, the Y-VA would morph into the Model 32A. With continuing improvements, the Model 32 would be offered into the 1950s—mostly used as large stationary engines driving generators or pumps.