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Running engine in reverse Harmfull?

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Old 06-14-2003, 02:32 AM
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rustyrivet
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Default Running engine in reverse Harmfull?

Any of you guys an authority on running big glo engines backwards??

I'm breaking in my Moki 2.1 with 2-3 minute runs. I've got the test stand in my storrage shed and am standing from behind the engine when I start it. This way I can back out of the shed and close the shed doors on this noisy son-of-a-gun while it breaks in. (Do you know what was still noisier then when I first ran my engine out in my open patio? My wife complaining about it! )

Ooops........well it CAN get confusing when I have to kneel in back of an engine and start it from behind. I THINK I MIGHT HAVE BEEN KICKING IT OVER AND RUNNING IT IN REVERSE A FEW TIMES?????? :stupid: I know it did start up more than once when I manually flipped it past the compression cycle backwards. (Lighting is so darn dim in the shed, I couldn't see which direction the prop was actually spinning once it started -I'm hoping it might have automatically righted itself.)

Is running it backwards a bad thing to do to a new engine???
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Old 06-14-2003, 02:42 AM
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DBCherry
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Default Running engine in reverse Harmfull?

While most glow engines can start backwards, applying throttle will usually cause them to quit. I doubt that it ran backwards for long. It's fairly common practice to flip larger four strokes and gas engines backwards against compression when starting. It usually causes them to bump into a forward spin then start.

Aside from that, if it did run backwards I don't think it would cause serious harm.
Dennis-
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Old 06-14-2003, 01:52 PM
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Default Running engine in reverse Harmfull?

Originally posted by DBCherry
... fairly common practice to flip larger four strokes and gas engines backwards against compression when starting. It usually causes them to bump into a forward spin then start.

-
Dennis,

I was affraid that this method of "Backflipping" an engine to start it, might be misconstrued with what I was describing.

When "backpflipping" an engine, you bring the prop up to the point of compression, and then flip it backwards(clockwise, in the wrong direction) away from the compression . The prop then loosely bounces down the stroke and starts up automatically correcting itself and running in the proper counterclockwise direction. What I was doing was actually bringing the prop up to the point of compression, and then quickly flipping it clockwise tightly through the compression. When it starts in this manner through the compression, I can't tell if it continued on its merry way in the wrong direction. Or if it quickly reversed itself, but is too fast for the eye to see.

You know when you start an engine using a starter by driving it in the proper counterclockwise direction, it always starts and stays going that way. Now whether a single flip
by hand has a tendency to correct itself, I don't know. Hence, why I figured it would be safer for me to just assume that I had it going the wrong way, and ask if that is a bad thing to do.

I can tell you that it sure makes a wind blowing back to me as if it was going in the proper counterclockwise direcction. (But maybe big 20" props make a big wind no matter which way they're going, and I can't use the feel of a breeze as an indicator alone?)
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Old 06-14-2003, 01:54 PM
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Default Running engine in reverse Harmfull?

Doesn't hurt them most won't take much throttle before stopping anyway.
Chip Hyde the last TOC winner use to have an Ultimate bipe he would land and had a way to reverse the engine and would back the plane into its landing spot.
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Old 06-14-2003, 02:31 PM
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Default Running engine in reverse Harmfull?

If you can feel a wind blowing over the engine it's running in the right direction. Big props work the same way small ones do.
Steve
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Old 06-14-2003, 05:33 PM
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Cactus.
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Default Running engine in reverse Harmfull?

when flick starting a engine running backwards is normaly a sign it was primed too much, a few blips with throttle will sometimes get it confused enough to spin the right way again
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Old 06-14-2003, 06:33 PM
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Default Running engine in reverse Harmfull?

In hindsight it seems to me it might have been automatically correcting itself and was kicking into counter clockwise rotation even though I tried so hard to make it run asz backwards. :stupid:

I might not have had the sence to know which way to push the prop while I was standing on my head and looking at it from reverse. But I sure did know before anything else, that in the limited 40" space I had in this tool shed, it was better to start the engine kneeling from behind it, so when it did start I could practically fall out of the tool shed doors and be the heck clear of that spinning 20" prop and all the accumulating exaust.


Thanks gentlemen for the helpfull input.
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Old 06-14-2003, 07:41 PM
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Default Running engine in reverse Harmfull?

If you can feel a wind blowing over the engine it's running in the right direction.
Not really true Steve. If the prop is on backwards it will still blow air backwards, just not as much.

If that weren't the case they wouldn't have to make "pusher" props, we could simply turn our props around.

Chip Hyde the last TOC winner use to have an Ultimate bipe he would land and had a way to reverse the engine and would back the plane into its landing spot.
Chip must have had a Tx controlled variable pitch prop.
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Old 06-15-2003, 03:54 AM
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Default Running engine in reverse Harmfull?

O.K. Silly me. I'm assuming this fellow knows how to put a prop on correctly.
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Old 06-15-2003, 11:49 AM
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Default Running engine in reverse Harmfull?

Reed-valve engines run backwards with the same enthusiasm as forward. The old Cox Babe-Bee is an example.

One manufacturer of jet-skis has twiddled with the electronics to get reverse out of his jet-ski motor. These are also reed-valve motors, but have spark ignition. If you hit reverse, the electronics shut down the motor, then just as it stops, the spark plugs begin firing with revised timing to make the motor run in reverse rotation.

In 2-stroke with rotary valve such as the typical glo engine, nothing gets damaged from running backwards, but the rotary port timing makes sure that it runs crappy...it's just not getting enough air/fuel to run properly.
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Old 06-15-2003, 12:35 PM
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Default Running engine in reverse Harmfull?

DB Cherry

No Chip Hyde did not have a reverse pitch prop. As I recall he would shut the engine down for an instant and hit the throttle it would run in reverse. I have no idea what the settup was. This was not at the TOC but at a dry lake near Vegas where the QSAA was held.
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Old 06-16-2003, 12:55 PM
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Default Running engine in reverse Harmfull?

I don't think you Moki was running back wards. The instructions for the Moki actualy advises backflipping the engine. Mine starts most every time with just attempt, I spin the spinner backwards against the compression the engine backfires and spins in the right direction faster than a starter can spin it.
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Old 06-16-2003, 09:01 PM
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Default Running engine in reverse Harmfull?

Originally posted by Mustang Man
O.K. Silly me. I'm assuming this fellow knows how to put a prop on correctly.

Thanks for giving me that much credit. I think even a pure homogenized idiot would be suspicious about putting the side of the prop with the print all over it to the back. :stupid: But I guess I can't blame folks for being suspicious of my basic knowledge when asking such an unusual question.

Most folks have never been forced into a weird position in a tight little tool shed, and have to spend half the day flipping a prop from BEHIND the engine to break it in during many short 3 minute spells. I've done other 3 minute things in tight and weird positions, but mother nature usually takes over automatically and makes sure it goes right.
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Old 04-07-2005, 05:43 PM
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Default RE: Running engine in reverse Harmfull?

I have a 4 stroke O.S .91 surpass engine and the prop started spinning it the wrong direction. The plane moved backwards... What is the problem?
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