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Old Sep 17, 2003, 09:47 PM
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Walled Lake, MI, USA
Joined Feb 2000
11,182 Posts
Self-Centering Prop with Prop Saver

I recently switched over to running a GWS prop saver on my EPS-100 gearbox with M100 motor and GWS Hyper Drive prop. I was concerned at first that the prop would not center correctly on the prop saver, and would be out of balance. So I used a nylon washer that just fit into the large nut impression on the HD prop, and also just fit the nub of the clipped gearbox shaft. This worked fine, and the prop was always in balance.

Yesterday I was fiddling around with props, and when I started to run the motor up, the prop was way out of balance. I shut it down when I realized that I'd left the washer out. Just for the heck of it, I slowly ran the motor up again, and the prop was still out of balance. However, when I got to about half throttle, it started smoothing out. And by the time I got to full throttle, the prop was spinning smooth as silk.

So I went out and flew it with no problems at all, and repeated that tonight. I can move the prop around on the prop saver pretty easily when it's not running, even with a fairly tight O-ring holding the prop to the prop saver. But every time I run the motor up, it appears that the prop self-centers into perfect balance.

I've probably read millions of words of advice about e-flight. But I don't ever recall reading anything about props self-centering on a prop saver. Have I only now just discovered something that everyone already knew about?
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Old Sep 18, 2003, 05:08 AM
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vintage1's Avatar
East Anglia, UK
Joined Sep 2002
29,705 Posts
Its very unusual for any rotating mass to self-center on a shaft. The reverse is true - it tends to flt off if it can. I can only think the vibration is allowing the prop to shift, and the rubber bands pull it into balance.

Or that the vibration is still there, but the frequency is high enough that its more or less unnoticeable.
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Old Sep 18, 2003, 07:19 PM
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Walled Lake, MI, USA
Joined Feb 2000
11,182 Posts
Interesting. Hoppy wrote in another thread: Believe it or not, the prop seems to center itself when using the prop saver. I've used props with a larger hole than the nut and it seems to work OK.
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Old Sep 20, 2003, 01:53 AM
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Happy|Harry's Avatar
Aberdeen, Scotland
Joined Jul 2003
6,972 Posts
The next time your out run the motor up as usual, then move the nose of
the plane up and down (or L to R simulating turns/climbs) and you'll see
your prop un centre it's self very quickly. Yes in a straight line it will seem
true but when any lateral force is applied to the prop it will move.

phil
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Old Sep 20, 2003, 07:29 AM
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North Highland,ca
Joined Dec 2002
551 Posts
Machinest have verious methods of centerungs shafts to hole centers Usally the beter the centering the longer it takes. if you make a hard sleve to fit the prop as you make the hole for the hub in the same machine is better. CU
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Old Sep 20, 2003, 10:12 AM
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Walled Lake, MI, USA
Joined Feb 2000
11,182 Posts
It's no problem for me to pop the nylon washer back in and get positive centering. All I can say is that I've seen absolutely no difference in performance flying without the washer. Again, the O-ring I'm using is quite strong. So it takes a pretty good force on the prop to get it to move. But it will pop off in a prop strike situation.
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Old Sep 20, 2003, 11:36 AM
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Alberta, Canada
Joined Sep 2001
1,292 Posts
I tried some heat shrink on the shaft and it makes it a lot less wobbly. It isn't a perfect fit bit it seems better on the bench. Flying will tell.
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