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Old May 18th 07, 11:20 PM posted to rec.aviation.piloting,rec.aviation.student
Peter Dohm
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Posts: 1,754
Default Proping Question

People will say it is technically impossible, but I think it is
wishful
thinking. An engine may not run backwards very well,

During World War II (really!) I worked on a farm in Concord, Mass.
There was a great steel-wheeled tractor that was started with a hand
crank. One time the tractor backfired while the lad was spinning the
crank, and the engine started running backwards. He jumped aboard

and
had a great time wheeling it around the yard, one speed forward and
three in reverse. Blue skies! -- Dan Ford

That was a Diesel engine, correct?

My great uncle Ern was nearly killed by a Model T Ford that he
cranked up
and the engine backfired and ran backward. 'Course, that guy was

nearly
killed so many times...
--
Waddling Eagle
World Famous Flight Instructor

A Model T will not run backwards. Even if it did run backwards it
would in
no way would put your life in danger.


The Model T was notorious for running backwards momentarily and causing
the crank to hit people in the face or it would break an arm. Ern was
knocked unconscious and suffered a broken nose.

It will not run continuously backwards, but it will run for a stroke or
two, just enough to hit you hard.


That is called "kick back" and isn't "running backward" at all.

Matt


Technically true. But "kick back" also makes a propeller a very effective
finger remover.

From what I have heard those old Model T Fords were notorious; although I do
not know how much was a result of people advancing the spark in the hope of
getting the engine to start, or how much was due to overall timing being out
of adjustment such that the markings on the spark advance control were no
longer accurate.

What makes that almost on topic is the fact that magnetos can also be out of
timing for various reasons, including wear of the points and/or the internal
cam followers, and that a failure of the impulse coupling(s) can move the
timing from after TDC to before TDC during the starting sequence. :-(

Actually, this has been a very imformative thread. For example, I had never
known the mechanism by which a four cycle engine can diesel backward beyond
a single kick--even though I have seen older automotive engines do so for a
half dozen strokes!

Peter