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Old 02-21-2009 | 04:21 AM
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DarZeelon
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From: Rosh-HaAyin, ISRAEL
Default RE: Prop/thrust washer

ORIGINAL: Ken6PPC

By all means, buy an original replacement from the sources w8ye referenced above. You do NOT want anything that is a sloppy fit on the threaded end of the crankshaft! That would result in a lot of vibration, or worse.
Ken, I think not.


Any washer that is the correct size will do the job

If we take an extreme case of an improvised steel washer, with a thickness of 2 mm and an O/d of 30 mm; even if this washer does have a very sloppy fit on the end of the shaft (with a hole 1 mm larger in diameter than the shaft thread), the imbalance calculates to ~23.5 cubic mm of steel (specific gravity 7.8), which are 0.18 grams 1.5 cm from the center, or 0.12 grams/cm.

This is equivalent to an imbalance of less than 0.006 gram at the blade-tip of a 16" prop...


I don't think you can really feel such a level of vibration, at ~9,000 RPM, even if it was an electric motor spinning this prop...
With any single-cylinder glow engine, which inherently suffers from a partial primary balance, this will really be imperceptible.

...So much for using expensive magnetic balancers, for props intended for such engines...
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