Bessemer engine

Bessemer (Carruthers and Fithian).

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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.

The types of half breeds can literally number into the hundreds. Coolspring Power Museum research has identified at least 20 makes of steam engines still existing in the field, with many more existing only in old records or probably having passed entirely into oblivion. Approximately the same number of makes of gas cylinders and conversions have been identified. The total number of engine types would be the product of both! This, plus the interchanging of parts such as flywheels, certainly accounts for why no two half breeds ever look exactly alike.

Historically, the invention of the half breed seems to belong to Bessemer. Although several patents appeared about the same time, credit must go to Dr. Edwin J. Fithian of Portersville, Pennsylvania, who was described as a physician with a 'mechanical term of mind'. Practicing in an oil field area, Fithian recognized the need for a cheap internal combustion pumping engine that could utilize existing steam engine components. The idea of the half breed was thus born! In 1897 he completed and tested a 10 HP model but was turned down on a proposed sale to the Oil Well Supply Company. Needing a partner and a source of manufacture, Fithian turned to John Carruthers, a successful local machine operator. They also recognized the need for a friction clutch to transmit the power from their gas cylinder, and in 1898 the Carruthers-Fithian Clutch Company was organized. They moved to Grove City, Pennsylvania to start production and their successor, Cooper-Bessemer, continues at that location today.

The idea was an instant success. In 1898, an oil producer could convert his steam engine with a 10 HP gas cylinder and clutch combination for $120.00. A 15 HP unit could be bought for $175.00 and with practice, two men could easily complete the conversion in one day. Bessemer's chief customer, the South Penn Oil Company, wanted so many that they paid royalties to manufacture additional half breeds in their own shop at Allegheny, Pennsylvania. During the first three years of manufacture, 10,000 pumping units were converted in Pennsylvania and West Virginia.

During this time, of course, other companies were capitalizing on the idea and obtaining patents for minor design changes. These included Braden of Parkersburg, West Virginia, Gardner of Washington, Pennsylvania, and Palm of Butler, Pennsylvania. Many more were simply producing plain two-cycle gas cylinders that could easily be attached to any steam frame and doing so without patent protection or worry about infringement upon others.

It is interesting to note that some companies offered a half breed using all their own new parts. The 1914 Bovaird-Seyfang catalog offers a 'B&S Converted Gas Engine' new and complete using their two-cycle gas cylinder and their steam engine frame. These engines were offered in 12 HP, 15 HP, and 20 HP models and were advertised to meet the demand of a moderately priced gas engine. If desired, one could purchase the gas cylinder and convert his own steam engine.

Half breed engines can be divided into three main types, each of which are discussed below. These are the 2-cycle, 4-cycle, and the convertible which, although limited in production, includes both 2 and 4-cycle models.

Two-Cycle Half Breeds

By far, the most common type of half breed was the 2-cycle. This is due to their utter simplicity; all that was needed was to attach a 2-cycle gas cylinder to a steam frame and one could start pumping. There were no extra moving parts required except replacing the plain steam engine pulley with a clutch pulley. A steam engine could be started and stopped easily with full load simply by turning on the steam where a gas engine cannot, hence the need for the clutch. Otherwise the steam engine remained intact, using the original bed, crank, crosshead and flywheel.

Flywheels varied greatly, due to availability and desired inertia. Since most steam engines used in the oil field had a 31/4 inch crank shaft diameter (some used a 3 inch and some used a 31/2 inch), flywheel interchanging was usually no problem. By adding a second flywheel on the off side, a smoother running and nicer appearing engine was obtained. All the oil field type steam engines originally used only one flywheel to which 'balance rings' or extra weights could be attached for drilling or pumping deeper wells.

Ignition for early half breed engines was almost always the dependable hot tube. However, high tension ignition became available in later years with the advent of the Wico R1 and OC magnetos. But magnetos always presented a problem with worn parts and shorting due to moisture, where the hot tube was easily maintained and understood. Remember that at the turn of the century gas engines represented high technology to many, and the simpler the engine, the more oil that would be pumped.

Half breed fuel was usually natural gas, which was readily obtained from the well itself. It could power the engine and heat the hot tube and still be used in much smaller quantities than to fire a huge boiler.

Governing was sometimes by a simple flyball governor, usually a Pickering, or was more likely done manually. It was practical and more convenient to run the engine 'on the cock', which is to open the quarter-turn gas control cock to admit only enough fuel to maintain the desired pumping speed. Hence the reason for finding so many governors lying on the engine house floor. When the governor was used, it usually merely served as an overspeed device to control the engine whenever the well pumped off. Notable exceptions to this were the Bessemer and the White-Thomas, which both used pendulum-type hit and miss governors. Only one example of a White-Thomas has been discovered, but for the many Bessemers known, it is usually found that their governors have been disconnected and they are run 'on the cock'.

Some of the many types of 2-cycle cylinders are listed at the end of this article. It seems that every small oil patch foundry made its own version of the 2-cycle half breed. Figure 1, a photograph of an Oil Well Supply Cylinder on a Gibbs and Sterret frame on display at Coolspring Power Museum, is typical of the early 2-cycle half breed.

Four Cycle Half Breeds

The 4-cycle half breed, although similar in overall purpose, posed a more complex problem in conversion due to the addition of more moving parts required to operate the exhaust valve mechanism. Usually they retained the steam cylinder, converting it to gas usage. Advantages of the 4-cycle design include easier starting and more reliable running. The Coolspring Power Museum continues to research the topic of 4-cycle half breeds. There are five types known, each of which is explored below.

The Boardman (manufactured by Robert Boardman Company, Oil City, Pennsylvania)-This relatively rare engine retained the steam cylinder which was sleeved to close the steam ports. A new cylinder head was produced which carried the intake and exhaust valves. The original steam passages were then used as a cooling water jacket. Governing was either flyball or fixed length intake pipe. A timing gear was attached to the frame which meshed with a gear on the crankshaft, and a push rod operated the exhaust valve. The intake valve was automatic. These engines ran very smoothly and presented a pleasing appearance. The Coolspring Power Museum has on display a very unusual Boardman equipped with a gasoline-fired hot tube and a liquid gasoline pressurized fuel injection system, the only known example of this technology.

The Pugh and Tinsman, Bruin, Pennsylvania-This very rare engine again retained the steam cylinder and was converted in a manner similar to the Boardman. Pugh and Tinsman used hit and miss governing with either a vertical flyball or a pendulum. The valves are positioned vertically under the head with only the exhaust valve being power operated. Again, a timing gear and cam mechanism had to be attached to the frame. Examples of this engine represent local ingenuity and much crude blacksmith work.

The Evans, Butler, Pennsylvania- This engine represents a usual type Evans overhead valve cylinder attached to a steam frame. Although it appears well done and practical, only two examples are known to exist.

The Sheffer, Emlenton, Pennsylvania-This engine used a valve-in-head, ported, 4-cycle cylinder attached to a steam frame plus the further addition of a timing gear, pushrod and rocker arm mechanism. With a huge port and uncooled valve chests, it must not have been very successful. Two examples have been identified and governing is not apparent on either. Ignition was by hot tube. This is another example of local design to produce yet another half breed.

The Acme-Abel, Titusville Iron Works, Titusville, Pennsylvania-This engine is not a true half breed, being built from the ground up as a gas engine. However, it does use Titusville's heavy Acme steam engine frame, crank and cross-head assembly, factory modified to include the integral bosses and lugs needed for gas engine use. It uses their typical 20 HP Abel gas cylinder and a single Olin gas engine type flywheel. The governor is the hit and miss type in the timing gear as would be used on an Olin or an Abel. Since both Olin and Abel gas engines were being manufactured concurrently, the Acme-Abel's purpose is not clearly understood.

Convertible Half Breeds

This is a unique class of half breeds designed to operate on either gas or steam. Their purpose is discussed earlier in this article. There are four types known to exist, with a fifth shown only on patent drawings. This subject will be studied in more depth by the Coolspring Power Museum at a later date, but for this article each type is briefly mentioned below.

The Braden, Parkersburg, West Virginia-This design exists only as a patent drawing, but is significant in being the oldest convertible design, dating to 1898. It is simply a 2-cycle gas cylinder and a double acting D-valve steam cylinder mounted in tandem on a common frame. The patent implies that the gas cylinder is mounted ahead of a steam engine with the steam engine being modified by a stuffing box head. However the drawing implies an engine with a common frame under both cylinders. With no existing examples, this question appears lost to history, if indeed an engine was ever built. One does wonder if this is the same Braden that appears in Butler several years later building regular 2-cycle half breeds and clutches.

The Gardner, W. D. Gardner Convertible Gas & Steam Engine Company, Washington, Pennsylvania- This appears to be the first practical 2 cycle convertible half breed and has a 1904 patent. The Gardner design replaces the entire cylinder and uses a gridiron valve to isolate the steam chest for gas use. Hence, it can function as a regular 2-cycle gas engine or a regular D-valve steam engine. Although the company went into receivership about 1920, judging by the number of Gardners in use into the 1970's, it must have been a successful design. The next two designs mentioned appear to be copies of this machine.

The Either, B. D. Northrup Company, Washington, Pennsylvania- The Either, appropriately named, appears to be a close copy of the Gardner, the only difference being three in-cylinder mounted globe valves to isolate the steam chest and the intake chest. Local research implies that Mr. Northrup was initially a Gardner employee who saw the opportunity to start his own business. Apparently during the oil boom, demand was great enough to support both concerns. Although sometimes nicknamed 'Neithers', the Eithers appear to have been as successful as the Gardners. The fate of the Northrup Company included successful patent infringement lawsuit by Gardner. Later Eithers bore the Gardner name as the manufacturer.

The DC&U, B. D. Tillinghast Company, McDonald, Pennsylvania-Located in the oil field that boasted the largest gusher in Pennsylvania, flowing at 25,000 barrels per day, the DC&U represents the third 2-cycle convertible built in Washington County. This southwestern corner of Pennsylvania is the only area where the convertibles flourished and probably represents most of their production. It should be noted that these three firms also built plain 2-cycle half breeds as well. This engine represents the patent of Dahlberg, Clicquenoi, and Uhlin, and again is similar to the Gardner being either a 2-cycle gas engine or a D-valve steam engine.

The Palm, Butler, Pennsylvania- This is the only known 4-cycle convertible and represents the 1899 patent of George Palm. The cylinder is completely his product and on the near side carries a regular D-valve steam chest. A Stephenson link completes the reversing mechanism. The off side of the engine carries the intake and exhaust valve cages, with the latter being operated by push-rod from a gearless 'wig-wag' cross-over cam arrangement. Crossed helical gears operate a vertical governor behind the crankshaft which throttles the air and gas mixture. Ignition is by hot tube. By removing the push rod and turning a built-in quarter-turn cock, either gas or steam operation is obtained. The unique feature, and it is advertised as such, is that it can run on gas and steam simultaneously; a single acting steam engine behind the piston and a 4 cycle gas engine in front. But why?


This brief article introduces the reader to the interesting technology of the half breed oil field engine. This type of engine, produced mainly in western Pennsylvania, played a significant role in the oil field and yet is neglected by most collectors, historians, and the literature. It is hoped that this will contribute to the recorded history of the internal combustion engine and will increase the enjoyment of all those interested.


1. Keller, David N., Cooper Industries, 1833 - 1983. Ohio University Press, Athens, p. 33

2. Ibid, p. 34

3. Bovaird and Seyfang Manufacturing Company 1914 Catalog, Bradford, Pennsylvania, p. 52.

A Complete Outfit

A Bessemer Design Gas Cylinder Outfit consists of: One Cylinder with cylinder head and piston head, rod and rings complete; One Short Shaft Automatic Friction Clutch, 14 or 16 inches diameter; One Cast Brass Polished Cylinder Lubricator; Two Cast Brass Polished Grease Cups for crank and crosshead pin; One Hit-or-Miss Governor, with eccentric and eccentric rod complete; One Air and Gas Valve complete; One Bunsen Burner; One Dial Stop Cock; One Cast Iron, Gasometer-Acting, Dry Gas Regulator.