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I discovered that the aluminum fans I had are all badly out of balance. I had put them on the pulley and shaft and spun them by hand to see which one ran the most true only to discover the problem of poor balance they all had. Since I don't want to introduce a bad vibration to the engine, I want to balance them.
Is there a preferred method to balancing these given that they are difficult to mount for this purpose?
Suggestions welcomed.
Stephen
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How did you discover they were out of balance and are you sure they actually are - despite the "run true" test, Steve?
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26-12-2022, 06:27 PM
(This post was last modified: 26-12-2022, 06:27 PM by David Witton.)
Are we talking 2 blade or 4 blade, or both?
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26-12-2022, 06:49 PM
(This post was last modified: 26-12-2022, 06:54 PM by Steve Bryant.)
That would be both.
When I spun them they made my hand wobble. Not a scientific test but one that I'm pretty sure indicates imbalance. You could feel it.
Steve
I'd like to set up some way to be precise in checking the balance in the same manner as one would balance model propeller blades for example where they use needle points to give no friction to influence the heavy blade.
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Have you run the engine up, with one attached, yet?
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No not as yet as the engine has yet to be fired. The fans in question are not original but reproductions as near as I can tell which are not to the standard I'd expect from Austin.
If I can figure out a way to properly check the balance I'll let you know
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Try it first, you’ll know very quickly if it is at fault.
I have both original and repro ones (2 and 4 blade), none of which give any issue in use, might save you some hassle.
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Are you sure the fans are fitted fully home on the pulley? I've had repro fans/pulleys that have needed some slight easing before they fit together true and square.
Steve
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26-12-2022, 08:58 PM
(This post was last modified: 26-12-2022, 09:01 PM by Steve Bryant.)
Yes I checked for that. One of them isn't even machined square and the blades rotate in two different planes with one blade at a much coarser pitch than the other.
Ruairidh, I may end up doing that.
Stephen
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I balanced my 4 blade by sticking some small squares of lead to the tips with araldite and re painting g the whole afterwards to really bond them in place. Wash the bearings out , lube with 3 in one to reduce friction. Do your balancing, then lube with greave when happy with the balance.
