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Old Feb 12, 2009, 10:22 PM
I'm a Registered User
Evansville, WI
Joined Dec 2006
3,689 Posts
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How can I tell if my prop balancer is running true?

I made my own magnetic prop balancer. I bought one of those "finger tip" balancers that's basically a threaded shaft with points on the ends, and come cones to center the prop. I then suspended it between some rare earth magnets. It seems to work well with props down to my 4" GWS's. Now however, I'm trying to balance an EDF rotor and I'm having a heck of a time with it. It doesn't seem to be consistently out of balance, but I know it's not slipping and everything is tight. The rotor is so thick I'm only catching a few threads on the balancer shaft with the cones, and I think that might be causing a wobble. I'm also wondering if the drag of the points on the magnets might be throwing it off(it takes some extra magnets on the back side to hold the heavy rotor. Is there a way to tell if the balancer is out of true or if I just suck at balancing rotors? Thanks.
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Old Feb 12, 2009, 10:46 PM
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CooHead's Avatar
Northern IL
Joined Oct 2003
5,583 Posts
Beats me...but curious of the replys your question requests.
But tell me. Since you have balancer, I take it you do balance your props.
How often are they out of balance and how much does it take to get them into balance?
I've been flying for years. Have had to have gone through at least 100 props to date. Never a one has been balanced. I alwasy wondered about that. Like how much difference is there and/or how much "better" is a "balanced" prop?
I'm no expert 3D or IMAC guy. Just the weekender that breaks props all the time on harrier landings

Coo
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Old Feb 12, 2009, 11:30 PM
Registered User
Raleigh, NC
Joined Apr 2007
4,764 Posts
I balance all my props. Of course I use rather large props; 10" - 11" for my Slow Stick and since it's my AP plane I want to reduce all the vibration I can.

I use small pieces of electrical tape on the back side of the prop to balance it. I just move it toward the hub or tip as required to get it balanced. Takes about 30 seconds to balance one. However, my Slow Stick uses a low KV motor, too.

Other people sand away some material on the heavy tip, add a bit of clear fingernail polish, or a little dab of glue to balance it. I don't like any of those methods because they are so permanent. With the tape, if the prop needs balancing again due to a prop strike on pavement, for example, just peel the tape off and move it to a new location.

Below is a very simple prop balancer that didn't cost me anything. However I have now upgraded it with one of those finger balancers Jeff mentioned.

Bill
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Old Feb 13, 2009, 11:46 AM
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Xpress..'s Avatar
United States, CA, Alpine
Joined Oct 2007
20,936 Posts
It's pretty important to balance props, especially with an electric power system. An unbalanced prop will rob your motor of power and effeciency, so instead of you getting, oh lets say 200 watts with a balanced prop, you might only get about 180 or so watts with an unbalanced prop. And instead of 15 minutes per flight, you might only get 10-12 minutes.
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Old Feb 13, 2009, 01:15 PM
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theKM's Avatar
central PA.
Joined Sep 2004
20,189 Posts
unbalanced props represent wasted watts, and increased wear on motors
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