the steam cylinder oil tank is located under the front seats

Made of copper, the steam oil tanks on Stanley Steamers were always located either under the front seat floor boards or in later models under the front seat.  The steam oil tank has a volume equivalent to about two gallons of oil.

Only a minute amount of steam oil is pumped with each stroke of the steam oil pump when the car is in motion.  While the pump's piston stroke is several inches, the design of the pump limits the amount of oil pumped to approximately 1/4" of the full stroke or a few drops per stroke.  The Stanley Model 735 Operating Instructions suggest setting the pump to deliver a quart of oil every 300 to 500 miles.  Generally steam car owners insure generous lubrication is being provided to insure minimal wear to the engine.  Realistically many of today's Stanley owners consume a quart of steam cylinder oil every 100 to150 miles. 



Steam oil is often referred to as cylinder oil and compounded steam cylinder oil as its primary use is to lubricate the valves and cylinders of steam engines.  Steam cylinder oil provides a lubricating film to the engine steam admission valves (D-shaped valves in a Stanley engine) and the pistons within the cylinder walls.  Both the valves and the pistons are metal to metal sliding interfaces.  Steam oil must possess unique characteristics to allow it to mix with superheated steam, saturated steam, and hot water (condensate). Steam oils are manufactured primarily from mineral oils and are of viscosities equal to or greater than 600-weight oils.

Stanley instructions and manuals recommended the use of Harris Superheat Steam Cylinder Oil furnished by the A. W. Harris Oil Company of Providence, Rhode Island or Oilzum High Pressure Superheated Steam Cylinder Oil manufactured by the White and Bagley company of Worchester, Massachusetts for use with non-condensing cars.  When the condensing cars began to be manufactured it was necessary to change the consistency of the oil and Harris Condensing Steam Cylinder Oil from the A. W. Harris Company was recommended.  Near the end of production Stanley changed to using Atlantic 20th Century Cylinder Oil manufactured by the Atlantic Refining Company. 

The quantity of oil delivered to the steam engine cylinders of a non-condensing car was not too important as the oil did not return to the boiler.  The only condition to be avoided with a non-condensing car was insufficent oil being fed to the engine.   When the condensing cars were introduced the oil added to the steam and sent to the engine for lubrication returned to the water tank and eventually the boiler.  Thus it became important to limit the oil used to only what was necessary for proper engine lubrication.  The plunger type oil pump was found difficult to adjust to deliver the very small quantity of oil acceptable as a minimum to the engine. Consequently the oil was heavily diluted with kerosene (85% Kerosene to 15% oil according to Atlantic).  Now the pump could deliver oil in larger volumes and only a minimum amount of the oil actual oil would find itís way back to the boiler.  On the later condenser models such as 740, 745 etc; an entirely redesigned pump with ratcheting type pump was used which permitted very fine adjustment.  With this pump, which is mounted in the oil tank, undiluted oil is used.

Heating raw petroleum collected from oil wells and drawing off the vaporized gasses at different temperatures provides various products such as gasoline, kerosene, and diesel fuels as well as lubricating oils also known as mineral oils. Water will displace most oils, with the exception of animal based oils, and consequently special compounded oils that will lubricate in the presence of water are needed for successful steam engine operation. Modern steam oils contain 4% tallow by volume that comes from animals. Animal oil based tallow is produced by heating or boiling animal carcasses, and collecting the liquid residue. It is this tallow oil that makes steam oil work in the hostile internal environment of the steam engine. In practice the petroleum producers place several compounds in steam oil to help stabilize viscosity and lubricity; hence the name compounded steam oil.  Steam oils are manufactured in several blends depending on the temperature of the steam they are to be used with.

Steam pressure and temperature at the cylinder is the primary consideration in selecting the correct steam cylinder oil.  As a general rule the higher the steam pressure and temperature, the greater the need for a higher viscosity of oil, and the lower the amount of compounding which is required.  If temperatures and pressures are relatively low, then lighter viscosity oils with high percentages of compounding are most effective. Other mineral based oils such as internal combustion engine oil and machine oil must be avoided because they will not be able to maintain their lubricating properties in the presence of hot water and superheated steam.  The result will be metal-to-metal contact between the internal parts of the steam engine assembly, which will result in the scoring and galling of mating wear surfaces.

For additional information on steam cylinder oils see the Exxon-Mobil website.

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