| September/October 1991

Bashline Design, Inc., 2379 Lake Avenue, Allison Park, Pennsylvania 15101

The Coolspring Power museum is unique in its intense interest in internal combustion engine history. The following article was researched and written several years ago by the Museum staff. It briefly discusses the development and unique history of the oil field half breed engine.

The Half Breed Engine, or 'Breed' as it is affectionately called in the oil patch, is a steam engine converted into a gas engine. To our knowledge, this topic has not been addressed in any of the recent gas engine literature. Considering the proximity of Coolspring Power Museum to the old eastern oil field and its desire to represent locally built equipment of historical importance, the half breed engine represents a significant subject.

The half breed begins life as a steam engine, usually an oil field drilling engine, which is then converted to an internal combustion engine by either replacing the steam cylinder with a gas cylinder or converting the existing steam cylinder to gas operation. Several methods of the latter were employed, but all to the same end. The exceptions are the 'convertibles' that were designed to be easily switched to either gas or steam operation or in one case, for both simultaneously.

In the early decades of oil production, starting around the turn of the century when well productivity was decreasing, aging steam boilers were becoming unsafe and troublesome to maintain. It was no longer economical to fire a boiler for only a few hours of pumping each day. It would have been much easier to install a new gas engine that could be easily (hopefully) started whenever desired and run for short periods, without wasting the fuel to heat a great quantity of water in the boiler. However, at the time, the cost of a new gas engine presented a considerable expense. Therefore, it was much more economical to convert the old steam engine into a gas engine, which could be done at a fraction of the cost of a new engine. Soon literally scores of manufacturers of half breeds sprang up in towns associated with oil production.

The deviation in this trend was the convertible engine. This type of conversion gave the oil producer the flexibility of having a gas engine for intermittent pumping use while still retaining the smooth, dependable and reversible power of steam for servicing the well. For those unfamiliar, servicing included pulling the rods and tubing to clean and maintain the pump parts at the bottom of the well. Convertible technology was used primarily in the southwestern Pennsylvania fields.