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Forum Index : Windmills : A. of Attack-laser-fillm help!
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| domwild Guru  Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Phil, Found your suggestion of taping a laser pointer to the prop to get the angle and that seems to be a more precise way of getting the 13 deg. compared to the pendulum method. Like Pauline Hanson, when she heard the word "xenophobic" I have to ask: "Please explain!". I take it the props are perfectly vertical, then you tape the laser pointer to the concave side as per photo. Do you then measure the distance to the wall from the trailing edge and by trigonometry work out the distance the laser point should show when it is 0 deg. and when it is 13 deg.? tan 13 deg = (distance between 0 deg. to 13 deg.) / trailing edge to wall distance? or opposite to adjacent. The distance to the wall makes it very precise. How do you get the 0 deg. A.of A. laser spot? When the angle between the chord line and the prop axle is 90 deg perfectly, but how to you achieve that perfection? Do you use a long engineers or carpenters angle to get the 90 deg.? Your comments worried me as a one deg. diff. caused you problems with tower wobble and I have two left hands and surely will get it wrong. Excuse my ignorance: What is tip run-out? The three tips must be equidistant? 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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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Thats where all tips are in the same plane. If one blade is bent slightly foward, then you have tip run-out, because the tips dont follow eachother precisely. It can affect balance. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Dom, As Glenn has said " Tip Runout " is each blade should be tracking in the same path +/- 5mm is good enough, if you can get it better then thats good. If you think of a buckled wheel at speed it is the same . The Laser method is if you really want to get pedantic , the first blade is set at the correct angle and then when you rotate each blade into the "same position" the laser dot should align with the first set mark . In reality the wood blocks under the blades are by far the best easiest way to have each blade the same AOA . As long as the AOA is within 1/2 Deg on each blade is good as they are forgiving as long as they are set between 8~10 deg , if you go 9 ( 12deg Face ) all will be good. The Tower Wobble with the 1deg out from memory , it was just an annoying at a certian RPM caused the out of balance that I had chased for a while after rebalancing quite a few times. My Advice is " dont complicate it " get the tip to tip measurement the same and the run out good , set and lock the angle then balance . What Dia blade set are you building and what Alternator are you powering ... some pics would be good! PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Phil and Glenn, Thanks for that. I thought tip run-out is the distance from tip to tip, which also has to be equal for all three tips and that is another thing to get right. But that would be hard to get wrong with the PVC props. Looks like I am building a 2.8m dia. system with cogging F&P and hope this sledge-hammer approach will turn in our strong Easterlies (catabatic or gully winds) in the Perth foothills. This is Glenn's "overpowering" idea of overcome the cog. What I placed once on Fieldlines is my approach to Michael Lawleys (ecoinnovations) suggestion of a floating hub and when I dig up the photos again I will put them up here too. This time I am following Glenn's laser cut ideas for the PVC prop, before I had a PVC pipe prop and the wind would wind up the spring-loaded floating hub until the torque was sufficient to turn the cogging F&P. In the best case the prop would be able to turn close to 360 deg before hitting the hub and the momentum then would overcome the cog. Michael was and may still sell F&Ps with floating hubs unless he has changed over to Chinese mills completely. I cheekily asked him for photos or drawings of his floating hub idea but nothing came of it. Mine is spring-loaded to soften the "hit" and would also soften a star/delta switch. Floating hub is just another idea to get around cogging in addition to pole grinding, twisting, overpowering or buying a recent rotor. The cheapest pop rivet gun to pull the 5mm stainless steel rivets costs $54.90 and I have just ordered one. Managed to break two guns, one $10 one and a $20 one, which I both returned to Bunnings. As there is no warning message like "Do not use with SS rivets" Mr consumer is right. This latest pop rivet gun has 20 inch handles like the Kinchrome C960 model, which sells for more than $70. Guns with 11 inch handles are useless even if you had your Wheaties for brekki or are training for the London olympics. 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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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Phil or Glenn, While at the subject, what sort of a balancing method did you use? Simple turn and look out for the heaviest prop or the "fulcrum" method or?? As I do not have alu props with "C" sections to stick little rods into it is it just a case of adding more paint or what? The PVC/alu props should require little effort (weight) as the engineering is uniform. 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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