On Fri, 18 Jul 2003 20:47:48 GMT, (John
Flanagan) wrote:

On Fri, 18 Jul 2003 10:17:47 GMT, "Vaughn"
wrote:


"Walter Daniels" wrote in message
. com...

Actually, I have been thonking about this since it first came up. A
mVW, or other small(sort of) *air cooled* engine, would be the best
base. Feedingh steam through the intake and outlet valves, while
venting through the spark plug hole.

The intake valve is facing the wrong way so this scheme would only work
for very low steam pressures. Think about it; the valve spring would have
to be strong enough to hold the intake valve shut against steam pressure.
That is why most such schemes put steam into the spark plug hole. Either
way, you really have to do some design work on the intake valve problem to
make a practical engine, not as easy as just changing the cam.

I'm pretty sure you could ever get the engine to be a two stroke
without regrinding the camshaft no matter which way you do it. The
timing just isn't right. Intake opens on a downstroke while the
exhaust opens on an upstroke. You can switch this around but they'd
one would always be wrong.

John

There are two ways of doing this (and I've done one of them and it
worked):
1. change the crank to cam ratio from 2:1 to 1:1. Easiest is to do
this on a chain driven cam and replace the sprockets and chain. I've
seen plans for doing this conversion to a straicht six engine, they
just put normal old sprockets (both the same size) on the crank and
cam and connect them with a chain. You are right in that the timing
isn't quite right and that the valves are not going to be open long
enough to take advantage of the full stroke of the engine and you will
incur some pumping losses. That said, it would run, and for a
conversion you could do to an old engine in an afternoon with probably
minimal (or no) machine tools I'd say it fits the bill of what gunner
was asking for pretty well.
2. Do what I did with my little Briggs 3.5hp when I converted it,
just weld anothe set of lobes opposite the existing lobes on the
camshaft (a cardboard template helps), clean it up best you can, put
it back in, and just like that you have a steam engine. This will
make much better use of the full stroke of the engine so if you did a
good job of making your additional lobes this thing can run pretty
well.

Valves, not a problem. If we are talking about a home built
powereplant after the fall of civilization you won't have a nice burn
center to go to after your boiler explodes. For this reason I'm
thinking it would be best to shoot for a rather low pressure system.
I know in the early days of locomotives some were run at very low
pressures, might not be the worst of ideas. since the idea was an
easy conversion I'd say leave the valve train alone and run it as is.

Dave