Originally, the VW conversion engine was operated without the lube injection pump. It was hoped that splash from the crankcase would lubricate the piston rings and upper cylinder walls. Unfortunately the splash from the crankcase never seemed to reach the piston rings and upper cylinder walls. Scored cylinder walls and severe piston ring wear occurred during the operation of the steam 77 steam engine.
There is always positive pressure in the upper cylinder of a steam engine so there is no pressure difference to move the oil from the crankcase to the upper cylinder walls. In a four cycle internal combustion engine there is a suction stroke available every other revolution. This suction stroke permits splash from the crankcase to travel from the crankcase to upper cylinder walls.
In the VW conversion engine oil is injected into the clearance space between the inlet valve stem and the valve guide. Oil travels up the clearance space surrounding the valve stem into the space below the inlet valve. Thereafter the oil mixes with the inlet steam and is carried to the piston rings and upper cylinder walls. The oil is carried through the engine and leaves with the exhaust steam. The condenser condenses the oil and exhaust steam. The oil and water go through the centrifuge wherein the oil is separated from the condensate and the oil is returned to the crankcase.
In order for the oil to travel from the valve stem to the upper cylinder, oil pressure in excess or 1500 psi is needed.
Performance tests on this pump show it is capable of pumping up to 2000 psi or more and holding this pressure indefinitely. The oil injection pump in the Barrett Steam Car has been in use for 5 years. A recent test (conducted on 2 November, 1999) showed that either plunger was capable of pumping up in excess of 2000 psi and holding that pressure indefinitely. The pump uses o-ring seals on the plungers, inlet valves and outlet valves. These seals are easy to make and have excellent sealing ability.
The design concept of this pump can be applied to other steam engines
besides the VW conversion. Additional plungers could be added to provide
lubrication to crossheads etc. on an open crankcase engine.