my magnetic prop balancer

Here's a twist on a Great Planes "finger-tip" balance-shaft and the use of "rare-earth" magnets I got from Radio Shack. You've all seen the various magnetic balancers out there... Here's one you can build, if you like "building things"... (requests "smiley" with a hammer)

You will need a Great Planes "finger-tip" balance-shaft or equivalent, and "rare-earth" magnets similar to the one's "Radio Shack" sells in a 2-pack; which are approx. 3/16" in dia. x 1/16" thick. (see links below)

http://www.amazon.com/Great-Planes-Fingertip-Balancer-GPMQ5000/dp/B001BHK54W


http://www.radioshack.com/product/index.jsp?productId=2102642

My balancer has a prop capacity of 16.5" dia. (only because that's the size I decided to make)
Note: the largest prop I checked the balance on... was the largest I had; an APC 11 x 6

Here's a couple pics... Note: "Kavan" fingertip balancer shown... substitute w/"Great Planes"



I made a wood frame; consisting of a 6" sq. plywood base and top, with 2 uprights that were 1/4" thick x 1 1/2" wide (fir "lattice" would work fine) placed wide enough to accommodate the balance-shaft plus the magnets... plus a pair of 1/4-20 x 1"L. hex-head bolts; allowing for fine adjustment and expansion/contraction of the wooden frame. I CA glued the magnets to the two 1/4-20 hex-head bolts ends... and drilled/tapped the 2 wooden "vertical" pcs. to receive them... (tapping was a little excessive... but that's me...) My fixture is held together with 4 metal corner braces, but what's important is having the 2 adjustment points level... and "adjustable". The frame/base and top, could be however you choose to build it.

As with most magnetic balancers; the "needle-point" of the balance-shaft only contacts "one" of the magnets. The other end of the balance-shaft "floats" in the opposite magnets' "magnetic field". I personally think that this "concept" is as close as you're gonna get... to "accurately" balancing your props... which is very important for a number of reasons... less vibration... which equals; less wear on your engine, airframe, radio equipment and less fuel foaming.

What "my" design allows for; is the adjustability of the magnetic field that suspends the balance-shaft. I.E. you would "begin" balancing; with "both ends" of the shaft; in contact with "both" of the magnets... then "back-off" the adjustment-bolts; to where one side "falls off" because of gravity. Screw "either" of one side back "in" slightly until the shaft "floats" again; and lightly flick the prop to rotate it. If it falls again... adjust a magnet (bolt) "in" a little more... (Ideally... "pulsing" a little elec. fan on and off; to rotate the prop for final balancing is key.)

The little "cable" you see in the pics; is just a "storage-retainer" I made... so I don't ever lose the balance-shaft.

If anything is unclear/confusing... let me know. I'd be happy to clarify.

Roger