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Forum Index : Windmills : balancing blades
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| kitestrings Senior Member  Joined: 23/04/2014 Location: United StatesPosts: 102 |
I thought I'd move this to a new topic. On a recent post PhillM wrote: Phil, others, I'm curious what methods folks are using to balance their rotors. We've had satisfactory results balancing assembled rotors on smaller turbines, and using the moment method - comparing weight x distance to COG for each blade - but, I've always thought a dynamic balance method would be better if it could be done on the turbine. I've also seen turbines with perfectly balanced rotors go through an rpm range where a natural frequency of the tower or yaw-tube plays in. In one case a tower engineer we had worked with recommended a minor change in guy position and tension and the situation was remedied. I wouldn't have believed it if I hadn't seen it. ~kitestrings |
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| domwild Guru  Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Murdoch Uni in Perth has an RE field with mills and one mill yaws periodically as it is unbalanced. This must have been a donation to the uni. Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
kitestrings & crew This is just an idea, but I saw an appliance demonstration at a big box store back around 2000 and the company (General Electric?) was so proud of their "Auto-Balancing" washing machine that they tossed in a bowling ball, then flipped the switch to "Spin" and you'd think all hell would break loose, but no! Nothing happened except the thing spun up for a while with no noise or wobble; amazing. My thought is, why not investigate their method and apply it to your HAWT windmills? I build VAWTs, so, being basically a 'drag' machine, the notion of blade balancing is just preposterous. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Kite strings, I always balance my blades on a pole I have set up in my shed. As I have 4.2m clearance I can do a fair size blade set.On the pole I have a bearing housing mounted from a F&P and have removed the seals and washed the grease out of the bearings so they roll very easy . Then the heaviest blade will always sit at the bottom , tip run out can be checked as well as blade angle set . It is best to get the blades weight and COG as close as possible first and of course tip to tip close as possible. Doing it this way gives me very good results, mostly I can get with in 1~2 grams , as for other methods or trying to re-invent the wheel, I will leave that to others. Mac, I must try that... Throw a bowling ball at my blades to balance them 
PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| kitestrings Senior Member Joined: 23/04/2014 Location: United StatesPosts: 102 |
PhillM, This sounds like a solid approach for the rotor sizes I've worked with most recently. Many folks assemble the rotor and suspend it horizontally on a line. The problem with this method is that if the connection point is not exactly centered, you can still have imbalance. Your pole method avoids this, and ensures it is balanced concentric to the bearing it rotates on. 1-2 grams is very, very good IMO. Goudgeon (spelling?) Brothers (they were boat builders in the state of Maine) made arguably some of the best blades in north America for many years. As I understand it they balanced the larger ones using the moment method, and the tolerance IIRC was 1-2%. Mac, I haven't seen that demonstration, but a spin balance would be terrific if one could find a practical method. Thanks all. ~ks |
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