The Mysterious OD was a most unique oil engine built by the Bessemer Gas Engine Company of Grove City, Pa., named the Model OD. Nothing else was quite like it. But before discussing the engine, I would like to look at the history of Bessemer. We know the Bessemers as sturdy 2-cycle oil field engines that are still relatively common. But where did that name come from and what did it mean?
In 1896, Dr. Edwin J. Fithian, of Portersville, Pa., applied for a patent of a 2-cycle gas cylinder that could convert a steam engine into a gas engine. This was very successful and the “half-breed” engine was born. He soon teamed with John Carruthers, an excellent machinist and manager, to keep up with the demand. Not long after, a complete 2-cycle gas engine was also being manufactured. The new firm chose the name Bessemer Gas Engine Co. for their growing factory.
At this time, the steel industry was expanding in Pittsburgh, with the addition of the new Bessemer converter to make consistently high-quality steel. This was designed by Sir Henry Bessemer, 1813-1898, an English inventor who designed his process in 1856. To feed Pittsburgh’s appetite for iron ore, the Bessemer and Lake Erie Railroad was formed. The northern terminal was Conneaut, Ohio, where the lake boats could discharge their cargos of iron ore with the huge Hulett unloaders directly into the railroad cars. This railroad still exists today.
So with the name of Bessemer being synonymous with success and progress, why not use it for the new firm? It seems that the growing engine maker did just that. Note that this connection is the author’s supposition and not documented fact. With the oil boom in that era and the demand for quality engines, the business grew. They were always securing new markets and making improved design changes. After many mergers, Bessemer still exists today, although no longer in Grove City, Pa. Bessemer merged with G. & C. Cooper of Mt. Vernon, Ohio, in 1929 to form Cooper-Bessemer. The name was changed to Cooper Industries in 1965. Today, they are the Compression Systems part of Cameron International Corp., based in Houston, Texas.
In about 1915 Bessemer Gas Engine Co. entered the oil engine market with the Type IV oil engine. These were very durable and simple, 2-cycle, intermediate compression pressure oil engines using a very sensitive inertia governor. They are considered “semi-diesels,” as the compression pressure is about 250 psi so they need an external heat source to start. When under load, the external torch can be extinguished. This is very similar to the glow plugs used today in some automotive diesels. The Type IV was built in larger sizes and included the 180 HP twin-cylinder model weighing 12 tons.
So now we get back to the Mysterious OD. About the same time the company introduced the Type IV oil engine, the firm apparently saw the need to build a smaller but high-quality oil engine. The OD appeared in about 1916 and was not well received, so production ended in about 1925. In retrospect, this was a very high quality engine with features to be described, but probably was too expensive to build when the Type IV could do the same task. It appears to have been only in the 15 HP to 35 HP sizes.
Another part of the mystery is the model name of OD, while all other Bessemer engines were called a “type” (and number). Bessemer continued using the “type” designation until its merger with Cooper in 1929. One guess would be that “O” meant oil field use and “D” meant diesel. It would be interesting to hear what the readers think about this! But to confuse this issue more, they also built the “OD” as a gas engine with a high bar KW magneto and hot tube.
The OD was designed by Harold F. Shepherd, a professional engineer whose interest was oil engines. Born in 1889, the 1920 U.S. Census lists him living in Grove City, Pa., and his occupation as an engine designer for Bessemer. He secured two patents for the vaporizer of the OD and assigned both to Bessemer, which is patent number 1,466,346. He published a book in 1935, Diesel Engine Design, John Wiley & Sons, New York. This work is available on Amazon in used copies.
His patent, shown above, is a cross section of the head of the OD. This is what makes the engine so unique: Note the large plug in the head end with the “T” handle to facilitate easy removal. There is an external torch that directs its flame to the bottom of a pot-like structure, which is heated for starting. The fuel injector is located at the bottom of the head to spray directly onto the pot. This pot is an interesting device as it contains liquid mercury, and is externally heated on the bottom and water-cooled on the top with the fuel oil sprayed up into it. Mercury has a very high specific heat; that is, it holds heat very well and much better than water. Once heated externally for starting, the mercury pot controls the vaporizer temperature. When the engine is idling, the mercury pot maintains a high temperature to assure good combustion. But when the engine is under load, the mercury boils and its vapor is condensed on the top of the pot, which is water-cooled, and giving up its heat it drops back down as liquid again. This controls the vaporizer temperature so that it does not get too hot. It is noted that mercury boils at 672 degrees F. These pots contain 7 pounds of mercury and are securely sealed at the factory so the user has no contact with it in any way.
The OD had many other unusual features, including a chain-driven vertical governor head, a power-operated lubricator, an unusual fuel and injection pump, and a cylinder pop-off valve set at 500 psi. It seemed to have too many bolts to hold the head and cylinder in place, but then again this was a high-quality engine. Perhaps one of the most unusual features was the floating crosshead. There was one main pin through the connecting rod, the end of the piston rod and the crosshead shoes, allowing them motion to follow the guide bars. This was intended to reduce wear and maintain better alignment.
It is interesting to compare the rugged simplicity of the Type IV Bessemer oil engine to the lighter and more complicated Model OD. Apparently, Bessemer felt that each engine had its place, but the sales of the OD were small compared to the Type IV. Note that the OD was rated to operate from 160 RPM to 275 RPM, but could be used at 400 RPM for drilling.
After heating the mercury pot and replacing the plug in the head, one or two shots of compressed air sets it into operation. It idles very smoothly for a 2-cycle and is a joy to watch run. Reid Wellman’s engine, pictured at left, is serial no. 29034 and was shipped from Grove City on Sept. 23, 1922. It was used by the Buckeye Pipe Line of Ohio in its Mohican Station near Marietta, Ohio. It was belted to a 3-1/2-by-8-inch bore and stroke vertical National Transit triplex pump. These pumps were built in Oil City, Pa., and extensively used by the pipeline companies.
All OD oil engines were shipped with a 4-by-4-inch bore and stroke inverted Bessemer air compressor for starting. The compressor was an optional extra charge item for the OD gas engine. A smaller engine was used for the air compressor and it is interesting to note that the Coolspring Power Museum’s 4 HP St. Marys HO was the starting engine for Reid’s OD at Mohican Station. Amazingly, Buckeye chose one cantankerous oil engine to start another!
The Coolspring Power Museum’s 20 HP OD is awaiting restoration. It is serial no. 29037, only three numbers later than Reid’s engine. It was found in the back corner of an old oil field warehouse in the 1970s in the Oil City, Pa., area. Apparently it had been used in a National Transit Pipe Line station near there. The paint colors denote such usage. Close inspection will reveal the head with its removable plug for the starting torch and its massive array of bolts. The fuel preheater can be seen attached to the cylinder with the fuel and injection pump just behind. The well-finished governor head stands near the crankshaft. The flywheels are actually “spindly” but 6 feet in diameter, and the crankcase is covered with a nicely done sheet metal guard to contain the lubricating oil.
I hope you have enjoyed this brief history of Bessemer and its “mysterious” model OD. It was a well-done yet unusual engine with characteristics not found on any other. Some parts were very well-finished and there is lots of brass work. Yet other parts appear overdone and cumbersome. There are four ODs known in existence, and the author will appreciate any comments and additional information. Note that some opinions stated are those of the author.
Sincere thanks to Reid Wellman for providing some photos and information to make this article possible.
Please visit the Coolspring Power Museum this year for exciting events and new displays. We are looking forward to a great year. Please join us!
Gas Engine Magazine would like to thank Coolspring Power Museum founder Paul Harvey for allowing us to reprint this article, which originally appeared in The Flywheel, Coolspring’s monthly newsletter.
Contact the Coolspring Power Museum at PO Box 19, Coolspring, PA 15730 • (814) 849-6883
