POWER STEAM CYLINDER OIL PUMP
   

THE POWER STEAM CYLINDER OIL PUMP LOCATED IN THE FRONT OF THE PUMP BOX UNDER THE FRONT FOOT BOARDS

Every engine needs some form of lubrication.  Its been suggested that the only thing that drips more oil than a Stanley is a Harley motorcycle and that both drip to keep the pavement from rusting.  For the internal combustion engine, there is a spray of oil under pressure throughout the engine which provides lubrication.  Due to the design of the steam engine and the fact that there's no oil pump spraying the engine with oil another means of lubrication is needed.

For the early Stanleys the owner was required to take an oil can and squirt steam cylinder oil on all the crankshaft bearings, valve gear and eccentrics.  For later cars a splash oil bath arrangement was designed into the engine such that the spinning differential gear and the mating crankshaft gear splashed steam cylinder oil on all parts contained within a sealed enclosure.

To lubricate the pistons sliding within the cylinders the same approach as used with locomotives, stationary steam engines, and steam traction engines was employed by Stanley.  Steam cylinder oil, in small amounts is pumped into the steam supply line going to the engine.  Once inside the line the steam oil mixes with the steam to lubricate the cylinder walls and pistons.

 

 

HOW THE POWER STEAM CYLINDER OIL PUMP WORKS

If supplying sufficient water to the boiler is the most important requirement in operating a steam car (or any steam engine powered piece of equipment for that matter) then insuring the engine is being properly lubricated perhaps ranks second.  A piston pump powered from the steam engine crosshead for non-condensing cars or the rear wheel axle for condensing cars supplies steam cylinder oil for lubricating the engine pistons and cylinders.

The steam cylinder oil pump only operates when the car is in motion as it is driven off the rear axle of the car (on early Stanleys the pumps were driven from the engine crosshead) along with the water and fuel pumps.  Located in the pump box to the right of the front power water pump as shown in the drawing at the right, the pump has the smallest piston of all pumps in the pump box.  When pumping oil the pump must be able to overcome the maximum steam pressure in the piping between the boiler and the engine.  The pump is capable of delivering steam cylinder oil at greater than 600 PSIG pressure so that the oil can be forced into the steam line when the boiler is supplying  maximum operating steam pressure to the engine.

The pumps up through 1909 were of a ratchet design where a paw ratcheted a toothed wheel which caused a plunger to be driven into a cylinder and to force cylinder oil displaced from the cylinder into the steam line.  These ratchet oil systems had no winker and often malfunctioned causing severe engine wear.

In 1910 a piston pump was incorporated for pumping oil along with a winker.  The pump was installed under the driver's footboards and located alongside the "short stroke pumps" that were used in cars until 1914.  Driven from the right-hand crosshead wrist pin of the engine, a rocker arm arrangement reduced the 5" engine stroke to the required 1-1/4" stroke of the pump's piston.  A complex arrangement that did not include check valves metered the oil that was delivered to the engine (see the description at the bottom of this page).  This arrangement provided for a much improved lubrication design that included changing the engine so that a copper enclosure over the crankshaft end of the engine could allow for splash lubrication. 

In 1915 Stanley introduced the "long stroke pumps" which ran at a much slower speed and were a lot quieter than the short stroke pumps.  Long stroke pumps have a 4" stroke and use larger diameter pistons.  The pumping action was also simplified by going to a check valve design similar to that of the water and fuel pumps.  The check valve balls were 1/4" diameter.  Mounted on the right rear axle is the pump drive box.  The pump drive box provides gearing and a crank arm to drive the power pumps.  At the end of the crank arm the pump drive rod is attached.  The result is that the pumps operate at a much slower speed as a result of this design making them quieter (see the photo and discussion at the end of the power water pumps article for additional information).  Later Stanley changed to a pump that was integral to the steam cylinder oil tank.

The Stanley power steam cylinder oil pump on a condensing Stanley operates identical to the power water and fuel pumps.  As the piston is drawn out of the cylinder a vacuum is created which draws steam cylinder oil from the supply tank to fill the volume within the cylinder that the piston occupied.  The oil is drawn from the oil supply line and the steam cylinder oil tank into the pump through the suction check valve while the delivery check valve keeps oil from being drawn in from the delivery piping.

As the piston is pushed back into the cylinder the steam cylinder oil that has been drawn in now tries to run back out of the cylinder through the suction check valve that was open.  This action forces the suction check valve to close and pressure begins to build on the oil in the cylinder as the piston continues its motion into the cylinder.  When the pressure within the cylinder becomes greater than the oil pressure of the delivery piping after the pump, the delivery check valve opens allowing the oil just drawn into the pump's cylinder to escape and flow into the delivery piping.  Once the piston is fully inserted in the cylinder no more steam cylinder oil is supplied by the pump to the delivery piping and the cycle starts over with the piston being pulled out of the cylinder to draw in more steam cylinder oil.

The power steam oil pump in a Stanley is located below or at least at the same level as the steam cylinder oil supply tank.  This affords an easy way for them to be initially primed with oil.  Rings of graphite impregnated packing are used at the end of the cylinder to for a seal between the cylinder and moving piston.  Maintenance is generally required every couple hundred miles to snug up on the packing nut.

Adjustment of the amount of oil delivered by the steam cylinder oil pump on a condensing car is regulated by an adjusting clamp (shown in the drawing above right).  A short drive rod is attached to the power pump crosshead and rides in a guide attached to the floor of the pump box.  This drive rod has a metal tab on the end that slides along the steam cylinder oil pump's piston rod.  The steam cylinder oil pump's piston rod is extended in length so that it is also supported by the guide.  The pump's piston rod has a fixed stop near the pump and an adjustable bushing on the piston rod at the opposite end.  The drive rod's tab slides between the fixed stop and the adjustable bushing as it makes its 4" stroke.  By positioning the adjustable bushing relative to the fixed stop the amount of steam cylinder oil delivered by the pump can be determined.  Generally the pump is adjusted such that as the crosshead cycles through its 4" travel the steam cylinder oil pump's piston only moves 1/4" to 3/8". 

 

HOW THE SHORT STROKE OIL PUMP FUNCTIONS

The short stroke pumps used in the early Stanleys were driven from the engine's crosshead wrist pin.  This meant the pumps were cycled at engine speed or one pump cycle per revolution of the engine crankshaft.  With the long stroke pump design being driven from the rear axle the cycling of the pumps is greatly slowed.  With a 40-tooth gear on the engine crankshaft mating with the 60-tooth gear of the differential, combined with the 31-tooth tooth gear on the axle and the 70-tooth gear that drives the pump crank arm, the effective gearing reduces the pump stroke to 3.38 engine RPM to one cycle of the pumps.  Due to the differential being part of the gear train this number is an average as differing rear wheel rotation rates will change the engine to pump drive ration slightly.

The early Stanley steam cylinder oil pumps did not rely on check valves for the pumping action to occur.  Instead there were two moving cylindrical rods forming pistons which by their motion covering the inlet and outlet ports permitted pumping action to occur.  The pump's powered piston (indicated as "A" in the drawing) moves in and out of the main pump housing (indicated as "D" in the drawing).  When the powered pump piston moves out of the pump housing oil flows in to the void that is created (as the drawing configuration shows).  As the pump piston moves into the cylinder it closes off the supply port and traps oil ahead of it.  As the powered pump piston closes off the supply port a small amount of oil is trapped between the piston and a follower piston (labeled "C" in the drawing).  The follower piston is held in place, blocking off the outlet port, by a spring which seats against a pair of adjustment nuts.  The adjustment nuts determine how far inside the pump the follower piston can move.

As the powered pump piston continues to move forward, the slug of trapped oil being pushed by the powered pump piston pushes the follower piston into the spring compressing the spring.  After a little bit of additional travel of the powered pump piston into the pump housing the oil slug and follower piston move as a unit so that the follower piston clears the outlet port.  As the powered pump piston continues to move forward it forces the slug of oil into the outlet port of the pump.  The powered pump piston makes contact with the follower piston to clear all of the oil slug.  As the powered pump piston reverses its direction out of the pump housing the follower piston returns to its stop to allow another slug of oil to be drawn in.

Adjustment of the amount of oil pumped is controlled by the position of a pair of nuts locked on the follower piston's shaft.  If the pair of nuts are moved on the follower piston shaft such that there is less length of the follower piston to the adjusting nuts then more oil will be pumped because the follower piston will be adjusted towards the right.  Moving the pair of nuts on the follower piston shaft in the opposite direction lengthens the follower piston shaft length and reduces the amount of oil pumped.

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