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#2636 - 07/17/01 06:38 AM Balancing Ceiling Fans
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
The T-Bar Thread brings up this question...

What is the best approach for balancing ceiling fans? (Especially down-rodded ones)

Next to driving rods, it is my least favorite thing to do in our field...

Keep in mind that I balance propellers for my planes often, and the magnetic balancer works well for me. These props spin at 14,000 RPM! And in order to take pictures, it as to be very well balanced.
But I digress...

I have yet to try the weighing each blade on a scale to the nearest .1 gram, having trouble finding a scale cheap enough, accurate enough and that can weigh enough weight. .1 gram increments and a 5 lbs limit would work, but the local supplier wants $350 for it... I'd probably get put on some list at the sheriff's office if I bought one though...

My policy is to only balance fans on down rods... I'll usually hand the balancing kit to the customer and tell them they can save $20 or more by doing it themselves... I'm no good at it...

I probably think too much about aerodynamics, gyroscopic precession, balancing assymetrical things (five blades)etc...

Any tips? It's probably simpler than I'm making it out to be...
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#2637 - 07/17/01 01:23 PM Re: Balancing Ceiling Fans
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
I'll usually hand the balancing kit to the customer and tell them they can save $20 or more by doing it themselves... I'm no good at it...

boy i've been doing that for years! usuaually i'll get it close by swapping blades first.



seems those cast iron hunter's don't have this problem.......

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#2638 - 07/17/01 02:29 PM Re: Balancing Ceiling Fans
Tom Offline
Member

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
I usually leave the screws loose by 1/2 to 3/4 of a turn (the ones that attach the metal yoke to the fan and not the ones that attach the blades to the yokes). Turn the fan on high & run for a minute, turn off, allow to coast to a stop, try not to move anything & tighten up the screws. This usually does a good enough job so that you won't be messing with the balancing kit.

Wobble is another reason why I hate these dad blasted things.

Tom
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#2639 - 07/17/01 03:02 PM Re: Balancing Ceiling Fans
Anonymous
Unregistered


>I have yet to try the weighing each blade on a scale to the nearest .1 gram, having trouble finding a scale cheap enough, accurate enough and that can weigh enough weight.
It would not help you much anyway.

The torque from a fan blade is your good old foot pound, not vanilla pound.

5 grams near the spindle makes little difference compared to 5 grams out at the tip.

You need something comparable to a tire spin balance computer.

>balancing asymmetrical things (five blades)
Actually, five blades are symmetrical when spaced 72┬░ apart.


[This message has been edited by Dspark (edited 07-17-2001).]

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#2640 - 07/17/01 03:51 PM Re: Balancing Ceiling Fans
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
It is symmetrical on five axes converging at the center, not on one axis...

A two blade 12"D x 4"P Topflight Propeller balances easily in comparison because of this...

That is what I meant...
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#2641 - 07/17/01 06:56 PM Re: Balancing Ceiling Fans
Anonymous
Unregistered


>It is symmetrical on five axes converging at the center, not on one axis...
To me symmetrical means that there exists a line along which I can cut a pattern in half, hold it against a mirror, and see a whole. That makes a ceiling fan quite symmetrical. As you point out, there are at least five such lines.

A propeller by comparison has just two such lines.

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#2642 - 07/17/01 07:47 PM Re: Balancing Ceiling Fans
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
Sorry if I misuse terminology...

I'm a master of malapropisms, spoonerisms and any other grammar malformality.

I grew up in WV where they say "tar arn" for a tire tool and "far" for fire and things like "tarnation" are used regularly.

Try to listen to what I mean and not what I say... and I'll try to be more precise.

 Quote:
A propeller by comparison has just two such lines


If you assume a two blade prop. Like fan blades, they too can have three, four or even five blades (common on WWII fighters like the Sea Fury and later 'Stangs, to soak up all that HP! pardon whilst I drool) again, the complexity of balancing such props increases exponentially.

Draw two lines intersecting a two blade prop at the center of the hub, one verticle and perpendicular to the centerline of the blades, and one horizontal along said centerline. Call each quadrant A (top-left) B (top right) C (bottom left) and D (bottom right). First you balance the prop so that the A/C side is even with the B/D side. Then still you must balance to see if the A/B side differs from the C/D side as well.
With a magnetic balancer, I can acheive prop balance in excess of the two-stroke motor that it is attached too very regularly.

Ceiling fans are a whole different ballgame even with what I know about prop balancing!

[This message has been edited by sparky66wv (edited 07-17-2001).]
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Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#2643 - 07/17/01 07:56 PM Re: Balancing Ceiling Fans
Anonymous
Unregistered


A tar has an infinite number of lines of symmetry. That does make it particularly harder to balance.

The old wheel balancers were just a level bubble on a pivot. That could work with a fan if only the paddle assembly could be separated from the motor.

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#2644 - 07/17/01 08:04 PM Re: Balancing Ceiling Fans
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
I like that idea...

I've seen guys assemble the fan and hang them horizontally from a table to check for the heavy blade...

This seams to be similar to the prop balancing practice, but I've never wanted to hang a fan with the blades in the way and have never tried it (yet).
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#2645 - 07/17/01 08:38 PM Re: Balancing Ceiling Fans
Morb Offline
Junior Member

Registered: 07/17/01
Posts: 1
Loc: Salem NH USA
Hey all,

New to this, i love it! My trick for ceiling fans is to measure from the ceiling to the outermost tip of the blade, and spin fan by hand to each blade, and make sure they measure to the same distance. If you have a wobble, one blade is most likely higher or lower than the rest. Give a tweak up or down and that should do it! It works 99% of the time for me! Thanks for letting me give my .02 $.

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