What about looking at either 2-stroke engines or the rotary Wankle engine from a Mazda RX7. The rotary is a much simpler design with only 1/3 the moving parts of the traditional piston engine. A big problem that I see in any of these cases is rust. All these engines are normal steel designed to be lubed and run on petroleum products. Isn't water, especially hot pressurized steam going to rust them away?
Offered by Michael.
2 stroke engines suffer from the disadvantage of having totally fixed valve timing, normally a rotating valve in the crankcase
and their only supply of lubrication is the fuel. Secondly aluminum is corroded to a far greater degree by steam than steel. A
2 stroke engine crankcase housing is almost always aluminum (like a modern 4 stroke). Rotary engines suffer from a far
greater disadvantage however - you simply cannot get them. The standard type auto engine however has the benefits of
being very cheap and very available, and can be converted to a 2 stroke motion by throwing away the camshaft and using
the plug port as both an inlet and an outlet, it is also splash lubricated from the crankcase housing and the oil ring on the
Corrosion is a problem when using steam. It is also a problem when not using steam. Try not starting a car for 6 months and you will find it seized up. Corrosion isn't as much of a problem as you think the steam when in contact with the steel or cast iron cylinder walls will not corrode either. Its when we take the steam away and let the oxygen in the air get at the steel, that's when the problems begin. But there are many simple ways of getting over this. Bear in mind some steam locomotives are over a hundred years old and are still in good running order. They use cast iron cylinders and when worn out are lined with steel.
So in summery 4 stroke is commonly available and is easily converted to higher efficiency 2 stroke. It will suffer less from corrosion than the standard 2 stroke as the 4 strokes bores are lubricated and the only contact steam has is with aluminum - the crown of the piston and the cylinder head. Hopefully these will be partially protected by their coating of carbon (but its not guaranteed).
Offered by Clip.
No sir! Rotary's are awesome! They are so simple to maintain, and produce such a higher power output then any piston driven engine, and they have about 4 moving parts? Plus they can be tuned to be highly efficient. They are far from rare, and the parts are easy to come by. There are plenty of rotary engines out there, believe me. You can stop any motor from rusting with antifreeze and a can of CRC will stop the out rotor housing from rusting.
Offered by Nick.