The D.C. & U.

A Gas/Steam Convertible Engine for the Oil Field

D.C. & U. convertible cylinder

An early ad for a Tillinghast-built D.C. & U. convertible cylinder.

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This D.C. & U. was photographed in 1964, probably somewhere near McDonald, Pa., and likely when the engine was pulled from service.

This particular cylinder caught my interest while working with Joe Prinzinger on a historical document of the B.D. Tillinghast Machine Shop (see page 25 of this issue for the full history) in McDonald, Pa. While the D.C. & U. engine cylinder was one of the products that Tillinghast built, it was not of his own design. Tillinghast was the sole producer in building this unique and apparently once popular engine cylinder, and the patent rights belonged to three other individuals, Gustave Dahlberg, Jacob Clicquennoi and Ernest Uhlin. These three gentlemen all lived in the town of McDonald, and held May 1899 patent numbers 633338 and 633339 for their engineering design of this very unique cylinder.

The three inventor's relationship with B.D. Tillinghast is completely unknown. Were they personal friends, neighbors, or simply businessmen looking for the right partnership? What we do know is that their cylinder was extremely popular in the southwestern Pennsylvania and northern West Virginia oil fields.

The Convertible gas/steam engine is much different than your typical gas half-breed. As a half-breed simply turned an old steam frame into a gas-only pumping engine, the convertible cylinders could be used as a gas engine or a steam engine. The purpose behind such a concept was to allow an operator to use steam power when the gas reserves were not available, and the gas engine when the resources returned. It was much easier than constantly changing the gas and steam cylinders off of the well.

Although there were several companies that built and patented convertible engines, the D.C. & U. design seems to have stood out among the rest. The major noted factor was that the steam chest was used as a fuel/air mixing chamber, which allowed more room for a coolant chamber. Other designs used a separate charging area creating excess weight on the steam frames.

While studying the patents, I noticed some interesting facts. To begin with, the two patents that were registered show slight differences in design. The first patent shows the engine, although a 2-cycle, using an exhaust valve working off of the cross-head. The second patent shows a traditional ported exhaust, which appears to have been the more common of the two. The D.C. & U. cylinder also was built in a rotary steam valve configuration. An old price list is my only evidence to prove that this design once existed.

Last, I noticed an interesting difference from the earlier design of the cylinder. The patent design shows a D.C. & U. patented carburetor. In later designs, and in Tillinghast sales flyers, you can easily notice that the carburetor that was used was one of B.D. Tillinghast's own design, one he used on his Tillinghast gas cylinders.

The attached photo is a 1964 picture of a D. C. & U. This picture was probably taken somewhere near McDonald, Pa., when the engine was most likely pulled from service. The second picture is from a Tillinghast sales flyer.

This has been an interesting and exciting project. Over the next several months, I will continue to do research on two other companies in my hometown of Washington, Pa. Interestingly enough, these other companies were also builders of convertible engines. I would love to hear from anyone who has a convertible engine, and especially anyone that has or knows of a D.C. & U. or Tillinghast engine. Feel free to contact me at the address below. Also, if you have Internet access, be sure to log on to the OFES web site at I will post additional information and pictures of these great convertible engines.

Contact engine enthusiast Bill Tremel at: (724) 484-0311 or e-mail at: