May 2013

The Mysterious OD

By Paul Harvey

It is now May with nice weather upon us, and the museum's first open weekend is already history.  In about two weeks, on May 18 & 19, the museum will again be open with selected running displays and guided tours.  Then, in about one month, will be our big June Show featuring "Oil Engines."  Any engine that uses compression ignition and injects a liquid fuel will be included.  Of course, exhibitors are welcome to bring all their treasures and operate them in our display fields. 

So that brings us to this month's topic, The Mysterious OD.  This was a most unique oil engine built by the Bessemer Gas Engine Company of Grove City, PA, and was named the Model OD.  Nothing else was quite like it. But before the discussion of the engine, I would like to look at the history of Bessemer.  We know the Bessemers as sturdy two-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 two-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 two-cycle gas engine was also being manufactured.  The new firm chose the name Bessemer Gas Engine Company for their growing factory. 

At this time, the steel industry was expanding in Pittsburgh, PA, 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.  See Photo 1.  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 Heulett 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?  And so it seems that the growing engine maker did do that.  Note that this connection is the author's supposition and not documented fact.   Photo 2 shows the immense factory of the Bessemer Gas Engine Company in 1920 with the small insert showing it in 1900.  With the oil boom in that era and the demand for quality engines, the business grew.  They always were 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 Corporation, based in Texas.     

About 1915, Bessemer Gas Engine Company entered the oil engine market with the Type IV oil engine, see Photo 3.  These were very durable and simple, two-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 twelve tons. 

So now we get back to the Mysterious OD.  About the same time, the firm apparently saw the need to build a smaller, but high quality, oil engine.  The OD appeared about 1916 and was not well received so that production ended about 1925.  Note Photo 4.  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, when all other 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 reader thinks 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.  See Photo 5. 

The OD was designed by Harold F. Shepherd, a professional engineer whose interest was oil engines.  Born in 1889, the 1920 US Census lists him living in Grove City, PA, and his occupation as engine designer for Bessemer.  He secured two patents for the vaporizer of the OD and assigned both to Bessemer.  See Photo 6 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, as noted 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 the interesting device as it contains liquid mercury, 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.  Photo 7 shows Reid Wellman's 20 hp OD Bessemer with the starting plug removed and the flame against the bottom of the mercury pot.  These pots contain seven 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 this was a high quality engine.  Perhaps one of the most unusual features was the floating cross head as shown in Photo 8.  There was one main pin through the connecting rod, the end of the piston rod and the cross head 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, see Photo 9 for a cross section, to the lighter and more complicated Model OD,  see Photo 10.  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 to 400 rpm for drilling.