Balancing Blades

Discussion in 'General Questions' started by mark99, Jun 4, 2011.

  1. mark99

    mark99 WindyNation Engineer

    Hi, Guys

    I have just finished a 1000 watt windmill two weeks ago. We finely got some wind the other day and the power out put was great. It was a mixture of parts off of e- bay and parts I built and I was relived that it works well. The only problem I have is I get a vibration at about 100 rpms. None before and none over that. I had an adapter plate made at a machine shop to fit the PMA to a set of 10 foot diameter fiberglass blades. The bore is 7/8 of an inch. How would you go about balancing the blades? I tried a lawn mower blade balancer but it did not work well. Any input would be greatly appreciated. Thanks Mark new blades.jpg
  2. Andy R.

    Andy R. WindyNation Engineer

    Is that a"string"in the center of the shaft hole? Wouldn't that be a good way to balance the blades. It's odd that the vibration is only around 100 RPMS. Maybe it's not a blade balance problem.
  3. murray2paddles

    murray2paddles WindyNation Engineer

    Mark, good to hear your hard dork is paying off , well done buddy.
    I am assuming the vibration is when it is pole mounted and not bench testing !

    Where are you reading the vibration , on the pole ?

    If it s on the pole and smooths out past approx. 100 rpm, it may just be the power that those big blades are creating while starting up and that inertia Is creating some pole sway ! All your guide wires tight ?
  4. murray2paddles

    murray2paddles WindyNation Engineer

    Ha ha, man that really proves that we need to edit our postings . Mark I am laughing so hard right now I have tears in my eyes ! lol.
    You do know I meant " your hard work ".
  5. Andy R.

    Andy R. WindyNation Engineer

    Yeah murray. I figured you hit the wrong key or you knew him really well. LOL!
  6. mark99

    mark99 WindyNation Engineer

    Thanks for the responds guys,
    I sometimes think you had it right the first time Mur. LOL I see the tail shimmy a little that’s what made me think it was out of balance. This is a much heaver machine so I need to put another set of guide wires just below the blade sweep. I just wanted to check the balance while it was down. Andy the string is in the center of a lawn mower balancer because the pin that it sat on could not take the weight of the blades; still I could not get them to balance for any time. That’s why I was hoping someone had an idea. I did find that one 12 mm bolt that holds on the blades was a ¼ inch shorter then the rest so I did replace that. It will be down for a few days until I get the extra cable and weld the cable ties to the pole. Murry, you have given me reason for hope that it may be normal. This mill cranks out some power though, it blew a 50 amp fuse the other day in high winds. It is built to furl at 30 mph but have not seen these winds yet. Thanks Mark
    new windmill.jpg
  7. windyguru

    windyguru WindyNation Expert

    You can also try weighing the blades on an accurate scale to see if one or all three :) of them are different weights. Then you could file them to have the weights match.

    Murray does have a point. Maybe at around 100 rpm, the turbine hits cut-in voltage. Because this turbine is so powerful, it gets tremendously loaded down by the battery bank and goes into some type of harmonic oscillation. It is possible if you only see this at cut-in rpm. I am just speculating here.
  8. mark99

    mark99 WindyNation Engineer

    Thank you windy new cable ties.jpg new windmill4.jpg guru,

    That is another good idea. To be honest I think Murry is right. I welded the stays on yesterday and put it back in the air. I have it tied in to a GTI and battery clamped as per instruction from Larry and Murry. They have been a great help in bring me dragging and screaming in to the GTI world. Now that I am here I like it very much. The vibration starts when the GTI locks in. As you can see the furling system is a cross between yours and the other power. Both have been great web sights for windmill builders. Mark
  9. leamywind1

    leamywind1 WindyNation Engineer

    Wow Mark things look real good. I wanted to chime in hear on the unblalance thing. After you have tried Mur's and windguru's idea and hopfully it work but if not. Is there any chance you would have another set of blades kicking around you could mount to see if indeed the baldes you currently have on there are out of balance? Better yet do a vid for us. LOL
  10. mark99

    mark99 WindyNation Engineer

    Hi Larry,

    I do not have another set of blades that will turn this PMA. I think the blades are fine, what I worried about was the adapter hub I had built. I am a bit of a control freak and that is the part of this system that I had to farm out because I do not have that kind of equipment. My thought was even if it was slightly off center it could be compensated by balancing. I understand what you said about the out of box thing. You will have to forgive me here but this is what I do for fun. The next time I bring it down I will check it with a dial indicator and try to find someone with an old style tire balancing machine.
    The GTI works great! It was really windy a few days ago. It is just my wife and I home now and we use about 12 kwh a day. For the two windy days we used 7 kwh per day. The GTI was putting 450 to 500 watts out and not going to dump. It was really cool. Thanks again Mark

Share This Page