One of the rarest oil field engines is the 'Black Bear' sold by the Oil Well Supply Co. of Pittsburgh, Pa. Of side shaft design, Black Bear engines are very pleasing to the eye thanks to their many moving parts while in operation.
Black Bear engines were ahead of their time with features such as mechanically actuated intake valves, optional air starting, a water pump and a triple-redundancy ignition system. Engines were built in 25, 35 and 40 HP sizes.
One thing I don't know for sure is whether Oil Well Supply actually manufactured these engines, or if they were sourced from another company. Existing engines are few, but I was fortunate to track down a circa-1920 Oil Well Supply Co. brochure that describes the engines:
Black Bear Gas Engines
'Black Bear gas engines are designed to meet the most severe requirements in the oil country. All parts are made with a view of exceeding the strength actually required.
'The engine is of the four-cycle type with valve mechanism operated by a camshaft driven by spiral gears from the main shaft. Both inlet and exhaust valves are operated by the same cam.
'Governing is effected by means of a Pickering governor, which can be set to operate the engine at a fixed speed or can be controlled by a line operated from the derrick floor.
'The valves are of the poppet type. They are so placed as to receive full benefit of the water jacket surrounding the valve chest.
'Ignition is effected in either of three different ways: magneto and jump-spark system, hot tube or make-and-break system. The design of the engine is such that all three ignitions may be attached at the same time if so desired. Hot tube ignition is sometimes desired, make-and-break ignition is recommended for power house installations, magneto and jump-spark ignition for all other installations.
'A Wico magneto is furnished when the magneto and jump-spark system is used. It is operated directly from the camshaft and is mounted on a bracket.
'Air starter provision is made on the cylinder head for connecting an air starter.
'Lubrication: The main bearings are provided with chain oilers, which carry oil continuously from reservoirs in the bed plate to the shaft. The crank pin is lubricated by means of a centrifugal oiling system. The cylinder is lubricated by a sight feed oil cup, as is the piston pin. The spiral gears driving the camshaft operate in a bath of oil. Oil cups are provided for the camshaft bearings, also for the rocker arm bearings. The Black Bear engine can also be furnished with force-feed lubrication, if desired.
'The engine is built with a short crankshaft. On the pulley side, there is a flange built as part of the flywheel hub. To this flange is bolted the flange of a short shaft carrying either a straight clutch or a reverse clutch.
'An oil guard for the crank pin is furnished as standard equipment with each engine. If preferred, a case to completely enclose the crank can be furnished.
'Water jackets are very liberal in size, and the circulation of water is insured by a rotary pump, belt-driven from the engine.
'Flywheels are balanced to insure smooth running and are extra heavy. This makes the engine give a very steady motion both under light and heavy loads.'
As always, please call, write or e-mail if you would like a free membership in the Oil Field Engine Society (OFES).
Contact the Oil Field Engine Society at: 1231 Banta's Creek Road, Eaton, OH 45320-9701, online at: www.oilfieldengine.com e-mail at: email@example.com