"C J Campbell" wrote in message
news:2007051622171050878-christophercampbell@hotmailcom...
On 2007-05-15 05:59:05 -0700, "Doug Palmer"
said:

...
An engine can be made to run backwards. Model airplane engines do it all
the time, usually as a result of mixture that is too rich. Granted,

Those are two strokes and don't rely on valve timing to run. A buddy had a
Bultaco motorcycle that liked to do that - it was pretty funny when he
dumped the clutch not realizing that it was running backwards.

real airplane engines are different and have more safety systems, but I
could not say that it is impossible, especially given the enormous variety
in types of engines, magnetos, starters, and fuel systems you see on
airplanes.

If you turn a conventional four stroke engine backwards, what would have
been the exhaust stroke is now an intake stroke, and what was the intake
stroke is now an exhaust stroke - the air will flow backwards through the
engine from the exhaust to the intake so fuel will not find it's way in to
sustatin combustion. On the other hand, an engine can "kick back" for a
revolution or so - and that's enough to do the damage...

To make a conventional four stroke run backwards, you have to re-arrange the
location of the lobes on the cam.

Trivia: Kettering developed his electric starter after a friend was killed
when an automobile engine kicked back while he was starting it with a hand
crank...

--
Geoff
The Sea Hawk at Wow Way d0t Com
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