Coolspring Spotlight: Circa-1898 15 hp Evans-Gibbs & Sterrett Half-Breed

This 15 hp Evans-Gibbs & Sterrett featured a box bed design and had crankshaft and near-side flywheel that are original Gibbs & Sterrett pieces.

Evan Gibbs half breed

Circa-1898 15 hp Evans-Gibbs & Sterrett half-breed

Photo courtesy the Gas Engine Magazine staff

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Circa-1898 15 hp Evans-Gibbs & Sterrett half-breed
Manufacturer: Evans Mfg. Co., Butler, PA; Gibbs & Sterrett, Corry, PA
Serial no.: 146
Horsepower: 15 hp
Bore & stroke: 9in x 12in
Ignition: Hot tube
Governing: Throttle governed
Owner: Paul Harvey

This converted steam drilling engine demonstrates another variation of oil field ingenuity where an internal combustion cylinder replaced the original steam cylinder on an oil field steam engine that was originally used to pump an oil well.

The frame

The engine dates to 1885 and was made by Gibbs & Sterrett in Corry, Pennsylvania. “You can tell this was a fairly old drilling engine because of its box bed design where the frame of the engine is basically box shaped, flat on the top and the various components including the cylinder, the crosshead support and the two main bearing blocks are bolted to the flat surface rather than cast in with the base when it was manufactured,” says Coolspring’s Clark Colby. The connecting rod, crankshaft and near-side flywheel are all original Gibbs & Sterrett pieces.

The cylinder

The conversion cylinder, made by the Evans Mfg. Co. of Butler, Pennsylvania, is of 4-cycle design, which is unusual as most of the converted engines were 2-cycle.

Evans made gas engines from about 1900 to as late as 1930 or 1940. “This cylinder design represents a fairly early version in that it has a boss mounted at a 45-degree angle on the cylinder casting that we believe was originally intended to hold a piston-tripped igniter,” says Clark. “That igniter seems never to have been commercialized by Evans.”


In this case, the conversion included adding an Evans flywheel on the offside that took an Evans clutch, which is not presently installed on this engine. “You needed to add a clutch when you did the conversion because unlike the steam engine, the gas engine would not start under load,” says Clark.

“The other complication in having a 4-stroke conversion is that you had to add timing gears,” says Clark. “In a box bed design, that was somewhat easier because the cam gear assembly could just be bolted onto the same flat surface that held all of the original components, although you still had to add a timing gear to the crankshaft where there had been none originally.”

Another interesting feature is the remains of a hit-and-miss governor that Evans apparently used on some engines, but very few examples exist.

In other ways the engine is fairly conventional. It has simple overhead valves, with the exhaust valve being operated by a rocker arm. It has the mixer that mixes air and fuel at the top. It has a grooved wheel, sometimes called a telegraph wheel that had a rope wrapped around it. The rope went to the derrick to a similar wheel.


When the engine was found on a small oil lease near Chicora, Pennsylvania, it had mounted on the exhaust a thermostatically operated homemade valve that would drain the engine cylinder in cold weather if the engine stopped while it was unattended to prevent cylinder freezing. “We later found the patent for that thermostatic valve and apparently the pieces that were on this engine might have been the prototype that was made before the patent was filed,” says Clark. “The patent was issued to a gentleman in Chicora, Pennsylvania, so that ties the history of this engine all together.” The engine was brought to Coolspring in the early 1980s and is owned by Paul Harvey.

Learn more about this engine and 38 others in Coolspring: Discovering America’s Finest Antique Engine Museum and see them run on the Coolspring Museum DVD. Look for ordering information online.