In late 2005 Orval Hill contacted me with some pictures of his creation - he built a working experimental steam engine from an old ride on mower engine using a pressure cooker for a boiler. I was intrigued, projects like this have turned up before, but Orv's is different in that it is so clever, simple, and straight forward that just about anyone could build one. The remainder of this article is Orval's words and pictures - read on, hopefully you'll be spurred onto building one! The article and pictures are © Copyright Orval Hill 2005 All Rights Reserved, used with permission.


My idea for this project was two fold:

  • Convert an existing engine; and
  • To produce steam the modern way, like useing an induction heater or a magnatron as in a (microwave oven).

This would be a very cheap, easy and environemtally friendly way. The heaters being powered by an inverter and the inverter being powered by a simple battery. The engine in this experiment was taken from a ride on mower, converted then replaced in the mower proving it could do useful work. My idea is to convert any 4 cycle internal combustion engine to an external combustion engine using water for fuel. This can be done by changing the camshaft and crankshaft gears to a 1 to 1 ratio instead of the 2 to 1 ration as now used and by modifying the exhaust valve cam.Steam can be generated in  a boiler by using an AC induction heater or a magnetron as found in microwave ovens. Power for the heater comes from an inverter in turn powered from a 12 VDC battery.Using a 2 cylinder engine whose pistons are 180 degrees out of phase with each other, in other words when one piston is at Top Dead Centre (TDC) the other one will be at its bottom most position Bottom Dead Centre (BDC).Starting at TDC when the crankshaft starts to rotate and is 5 degrees past TDC the intake valve starts to open, allowing steam under pressure, to force the piston downward. At 170 degrees the intake valve closes shutting off the steam. At 175 degrees the exhaust valve starts to open and stays open till 355 degrees, thus expelling the spent steam and the cycle starts over again.For use over a long period of time, or continued use, the exhaust could be expelled into a condensor which would change the hot steam from a gas into a liquid. The liquid could be collected into a tank and returned to the main fuel tank to be used over and over again.


During my experimenting with trying to convert a 4-cycle internal combustion engine to a 2-cycle external combustion engine, I made some mistakes and what I did to remedy them.The first mistake was that I selected the wrong engine to experiment with, that is I selected a 2 cylinder engine that had both pistons at TOP DEAD CENTER at the same time instead of 180 out of phase, I wanted an engine that had one piston at the top of its stroke, when the other one was at the bottom of its stroke, this then would have given me 2 power strokes for every revolution of the crankshaft.The second mistake was that I selected the wrong pressure cooker for the job I wanted it to do. I selected an aluminum vessel, which was not a magnetic material that I needed in order to use an induction heater. I solved this problem by cutting out the bottom of the vessel and installing a steel bottom in the pressure cooker.I then had a problem with leaking; I solved this problem by using a high temperature gasket-forming compound.I used compressed air to do the experimenting with and to get the timing correct.

Orv's completed engine piped up to its pressure cooker boiler.


Orv's Pressure Cooker Boiler showing the piping and pressure gauge.


The piping within the pressure cooker to gather dry steam and to some extent super heat it.


I then had the timing gears, the crankshaft and the camshaft gears machined to where I could weld 2 bicycle sprockets, both the same size, to the machined down gears in order to get my 2 cycle timing that I desired.When I first tried to run the engine, with compressed air, it would only make ½ a revolution; this was because the compressed air in the cylinder would not allow the piston to return to the top of its stroke. I solved this problem by changing the exhaust valve cam, I welded stock on the leading edge of the exhaust valve cam, and then had it machined so that it would open just after the intake valve closed and then stayed open till the piston reached it’s top most position. The engine then ran great.To complete my experiment, I would then plug the induction heater into a 120 volt ac source and heat the water to a boiling point and get the pressure up to around 70 PSI before It would start leaking around the gaskets and therefore the pressure would not go any higher, but the engine ran fine at this pressure. I would then plug the heater into my 12 volt DC to 120 volt AC inverter, which ran off a 12volt battery there fore completing my experiment.






  1. Engine
  2. Battery
  3. Boiler
  4. 12 Volt DC to AC Inverter (mains voltage)
  5. AC (mains voltage) Induction Heater
  6. Throttle Valve
  7. Intake
  8. Exhaust
  9. Starter Motor
  10. Generator
  11. Fuel Tank
  12. Condensor
  13. Pump
  14. AC (mains voltage)
  15. 12 Volts DC

SOME RECOMMENDATIONSI would suggest using an older 2 cylinder motorcycle engine that have the pistons 180 degrees out of phase, (see NO-1 above) this way you would have 2 power strokes every revolution of the crankshaft, thus doubling the horsepower.Another idea would be to use a 4 cylinder engine, an automobile type, as this would insure of having 2 pistons 180 degrees out of phase. Remove 2 of the pistons and use say number 1 and 3. If the engine has a timing belt instead of gears, you might buy a crankshaft gear and install it on the camshaft, thus giving you the 1 to 1 ratio desired.You can contact Orval at orvalhill AT

Editors note: This project uses heating powered by mains AC voltages (ranges from 110 VAC to 270 VAC depending on where you live) and is suggested to use a magnetron instead of an induction heater. It also uses a considerable boiler space and is capable of producing hot steam. I recommend that you seek the guidance and help of an appropriately qualified Electrical Engineer and possibly a Mechanical Engineer before undertaking a similar project. While it is certainly not beyond the home workshop, it does utilise principals which if used carelessly or without knowledge could lead to injury or possibly even death.