Stover graduated from the Towne School of Engineering, University of Pennsylvania in 1920 and worked there all of his life retiring in 1964 and dying in 1981.  This steam engine and the monotube boiler that  came with it were a retirement project.  Stover did the pattern and machine work, having the castings made at a foundry.

In a letter from his son, dated November 20, 2012, I learn that the engine was to go in a compact car.

The beauty of Stover’s engine is that it has all of the advantages of a rotary valve steam engine without any of the faults.  A rotary valve can easily infinitely change cutoff and direction of rotation, with steam admission always starting at TDC.

This is achieved by using pilot valves.  There are some disadvantages of pilot valves and that is hysteresis in the system, complexity of manufacture, and some slight inefficiencies with leaking steam.  However, for a slow moving engine they work fine. 

Stover was reported to have been a refrigeration engineer professor at the University of Pennsylvania.  This engine came with a monotube steam generator.  The workmanship and design is excellent.  This is one of the very few pilot valve operated steam engines and we think that this is because of Stover’s refrigeration background.   It is a V-2 double acting uniflow with pilot operated poppet valves in the heads.  The genius of this design is in the valve control.  It is a belt driven rotor that uses a triangular shaped piece of sheet metal to lift small ball bearings off their seats to release the pressure in the pilot valve and thus actuate the poppet valves. The timing is changed from full cut-off forward to full cut-off reverse with a very short cut-off in between by sliding the timing rotor.  It has to be seen to be appreciated.  Then there is built into the pistons two very small auxiliary poppet valve counter flow exhaust valves that are automatically timed by the movement of the pistons the same as a bash valve intake valve is actuated.  This design is the ideal for a direct coupled steam engine powered vehicle because the valve timing is as easily controlled as a rotary valve without any of the sealing or leaking or wear problems or a rotary valve.  We have found nothing about Stover’s biography or when he made this engine or why he was interested in steam power.

Bio below.

(Note: Click on a picture and it will take you to a larger view, then you can enlarge it with your browser further.)

Emory Frank Stover, 88, died December 18, 1981 Gladwyne, Pennsylvania.  He was formerly director of the School of Civil Engineering at the University of Pennsylvania where he had taught for 46 years until retirement in 1966.  Survived by son, David Frank Stover. He was a specialist in hydraulics.  The pistons are of an unusual design, being almost like a trunk piston, although it is a double acting uniflow with a crosshead.  There must be a very good reason for the piston design and I have not figured it out yet. Stover spent the last 8 ½ years of his life working on this engine. The quality of the castings is excellent.  This engine design has complete control of the valves.  It is the ideal to which all other steam engines that want to have complete cutoff control aspire.