So I have this dinky little 2" diameter flywheel (that someone else machined). It's not well balanced, and it's driving me up the wall.
So how does one balance small rotating parts? All I can think of is either to put the shaft on a pair of razor blades or make a plug with a concave hole and balance it on a needle point. Are these the ways? Is there some clever way to spin balance them?
If you really want it balanced right, call some local automotive machine shops and ask where they send engine assemblies for balancing, and maybe a performance turbo shop or truck shop and ask where they get turbo wheels balanced. They spin balance them, just like tire shops.
-- Regards, Carl Ijames carl.ijames at verizon.net
He would be better off calling an aircraft instrument shop that balances gyros or a company that manufactures small motors. A static balance would probably get it a lot better, especially if the diameter to width ratio is very high.
John
That Razorbade balance method works for model airplane props shing up to
30,000 rpm. There is also a device called a Highpoint balancer used often to balance RC helicopter rotor assemblys. Check Towerhobbies.com
Cobble up two knife edges that are dead level and parallel. Put your flywheel on a round (meaning lathe-turned or ground) mandrel and put it on the knife edges. The way I used to balance motor armatures was I took 2 1-2-3 blocks (the kind with threaded holes you can really thread into) and threaded bolts into them with fender washers, and I got a piece of 1x1/8" ground stock and beveled it on the disk sander, cut it in half and pinched each half to a 1-2-3 block on the surface plate and then used the precision level to square things up. Once you have the knife edges and the mandrel the rest is easy, put the wheel on, mark the high side, drill a little on the rim, repeat. If the flywheel is way out of balance you might consider mounting it on the lathe and machining it some to get it a lot closer.
GWE
Tim, I balance 60,000+ RPM, 1" diameter miniature steam turbine wheels (for a steam dynamo) on an arbor (sewing needle) rolling on a pair of single edge razor blades that have had the edges treated with a fine hard Arkansas stone to smooth them out. New raw edges break down quickly. Any heavy sidedness shows up easily. I drill near the edge until she shows no tendency to stop any any given place. Beware of balancing ferrous materials as any stray magnetic fields and residual magnetism in the part will react with it as well as gravity. Balancing a magetic rotor for the dyno is impossible statically.
Tim Wescott wrote:
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