high velocity fan blade not balanced?

I bought a high velocity floor fan with metal blades (model 9220). On the fastest setting, the fan vibrates slightly, but it has rubber bushing between the fan and the feet, so the vibration is isolated.
However if I wedge the fan in a window to use as an exhaust fan, the whole house starts to rumble since the fan cage is touching the window frame.
Is it common for this type of fan to vibrate due to off balanced blades? I don't see any counter balancing weights on the fan blades. I imagine they would look like those on a car wheel. I also don't see any holes drilled on the blades (another way to balance)
Is there a kit for balancing fan blades?
If fans blades are not balanced, I wonder about 40 inch fans or large. Wouldn't they vibrate so much they break themselves down?
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Your bigger problem seems to be the condition of your house if the whole thing starts to rumble when you misuse a fan designed to be used on the floor by wedging it in a window in an application it was clearly not designed for...
~~ Evan
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First of all, a Model number without a manufacturer's ID is a waste of everybody's time.
Standard way to balance blades is to try a penny and some masking tale, put the penny in the middle of one of the blades and see if the vibration increases or decreases. Label /number the blades a,b,c,d or 1,2,3,4 and use a notepad to keep track of things. Find out which of the four blades seems the best improvement. Then replace the penny with a nickel and repeat, again note which blade is best. Then repeat with a quarter.if you find one blade which is consistently where the money makes thing better, then try movong the monery toward the center and toward the edge of that blade. if you still need more weight, use two quarters and move then together in and out on the chosen blade. When satisfied with the results, a little JBWeld will secure the money where you want it to be. Don;t forget the weight of the masking tale will be offset by the weight of the epoxy so you don't have to worry about that. This is a matter of fine-tuning, you can spend 5 minutes or 5 days doing this, it's up to you to decide what is acceptable. It is better to use more weight closer to the center of the blade than to use a little weight/money on the outer edge of the blade.
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wrote:

Not really Bob...
If you try to use a fan that is designed and intended to be used on the floor only by wedging it in a window, no amount of trying to balance the blades is going to overcome the fact that you are using a system engineered for another purpose in a way it was never intended to be used in... Don't need any information about the manufacturer or any of that... A floor fan is a floor fan...
Would you be offering the OP advice if he was trying to use a ceiling fan installed vertically along a wall rather than horizontally under a ceiling ? You can't overcome a design application mismatch by trying to balance fan blades...
~~ Evan
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wrote:

Fans need to be dynamically balanced as well as statically. Putting pennies on a blade may statically balance a fan but not dynamically.
Think of it as one of the blades has slightly more"twist" than the others and there may be your (dynamic) unbalance problem.
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My recent experience with "low cost" fans (esp Air King) has been .......poorly balanced fan blade assembly & unacceptable levels of vibration.
http://www.homedepot.com/buy/building-materials-heating-venting-cooling-air-conditioners-fans-fans-floor/air-king-20-in-high-velocity-floor-fan-141978.html
cheers Bob
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On 9/3/2011 12:34 AM, DD_BobK wrote:

http://www.homedepot.com/buy/building-materials-heating-venting-cooling-air-conditioners-fans-fans-floor/air-king-20-in-high-velocity-floor-fan-141978.html
I have two upper-end fans that needed balancing. Fortunately. balancing fans is a pretty simple job. Is there some brand you recommend? It always seemed to me price made little difference when it came to balancing. But I've never spent more than a couple of hundred on a fan.
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Jim-
I have no brands to recommend. It seems like the quality of fans has declined greatly over the years independent of price. :(
Gresham's law applied to fans.
cheers Bob
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