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Forum Index : Windmills : Windmill broke!
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
Well after telling everyone about how strong I thought my new steel hub for the PVC blades was, it bent! The wind was gusty all day today, and when I got home I noticed something not quite right with the windmill. All the blades were bent back. 
I also noticed one blade was missing its tip. The windmill was still running ok, but a little out of balance. I dropped the tower to have a look-see. All of the blades show signs of hitting the tower. 
This is a close up of the broken tip. 
And this is where the blades bent back. 
Took the turbine off the mill, another close up of the bend point. 
I did find some of the broken bits, I'll glue these back on and reshape the tip, I'll need to shorten all the blades by 50mm to make them even. Any suggestions for a glue? Was thinking just super glue, its a clean break. 
Nelly assures me she had nothing to do with it. 
I'll recut some new steel supports tomorrow and fix the turbine this weekend. I'll cut the back plate from 6mm thick plate this time, double the thickness. The center hub was also cut from 6mm, its ok, but I'll cut a new one in 8mm just to be sure. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Gill Senior Member  Joined: 11/11/2006 Location: AustraliaPosts: 669 |
I'd be inclined to use PVC glue as it eats into the plastic and when pushed together forms more of a welded joint. With unknown plastics I do a test first. A drop of glue onto the plastic, wait 5 - 10 min, then scratch off with your fingernail. If it's eaten into the plastic thats the best to use. I always keep on hand Airfix(model aeroplane glue)and PVC glue but there is other stuff for other plastics.  was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| dwyer Guru  Joined: 19/09/2005 Location: AustraliaPosts: 574 |
Hi Glen Just before you start making steel support out of 6mm steel so why not use bis-alloy steel or high grade tensil steel is best away to go like 4mm instead heavy 6 mm mild steel 
dwyer the bushman |
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sPuDd Senior Member Joined: 10/07/2007 Location: AustraliaPosts: 251 |
A failure is a sign of progress Glenn, and a challenge to do better. 
If it were mine, I'd just weld a pair of bar stock steel pieces to the back of the hub where it bent. I have a feeling that even a 12mm thick hub would bend. I've noticed that the blade hub the otherpower boys use has this support built into the front, but they are using wood blades Vs PVC. 
sPuDd.. It should work ...in theory |
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| Feral Newbie  Joined: 03/12/2006 Location: AustraliaPosts: 39 |
Glenn, The PVC is weldable and its done with a LEISTER Hot Air Gun that is used by industrial vinal floor installers. I do not beleive that the normal PVC solvents will do the job and there is not many glues that will hold onto plastic in this situation. The welding rod is available from any pvc sheet supplier and its described as triple core and can be ground flat when finished and hardened. You will only require a small amount so that you can weld on both sides after you v joint the break. |
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Vasco Newbie Joined: 17/10/2007 Location: PortugalPosts: 6 |
Glenn, Pls note that PVC IS NOT WELDABLE i,e, it does not reach the strengh of the parent material at the joint...It can be glued, but the strenth is well below the native PVC. I would suggest to coat the blades (the concave part) with Polyester reinforced with fibre glass...(GRP) a car repai kit will do the job...the result will be a blade much stronger than the original PVC....you can obtain the strength that you want....just add more layers of GRP...if not stron enough you can go to a coat of GRE with EPOXI...or the ultimate Carbon fibre layer... Good Luck Regards Vasco |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
G'day Glenn, you could weld some angle iron on the back of the hub, triangles are pretty hard to bend. As for the blade, you have 6, with each one directly opposite, so why not just cut the broken one back and the one opposite? If you leave the others as they are it should still be in balance, shouldn't it?  Central Victorian highlands |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
I'll pick up some PVC glue this afternoon. The bit I need to glue on is only about 2 inch square, its not structual and under little load. If it comes off in the future I'll try a little fibreglass mat. I've recut the new plates. I found a scrap of 5mm Bis350, will be a lot stronger than the 3mm 250 grade of the original blade holders, and I've cut a new 8mm hub plate to replace the 6mm plate. Though the 6mm hub plate didn't bend, I figure if I make the blade holders stronger, then the hub plate may become the new weakest link, so best get in and upgrade it. I like some of the idea's above, especially Highlanders of shortening the opposite blade to balance it, very lateral thinking there. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
Well I put the windmill back up on Saturday, all working good. By time I packed up and went back to he shed it was putting out 15 amps. The dual stator with staggered winding is a "different" windmill. It sounds different, very distinct whine, kinda cool. And it seams to track the wind speed better, I think thats the staggered windings matching the conditions better than conventionally rewired stators. It speeds up and slows down very quickly with the changed in wind speed, all the while making watts. Its hard to describe, other than its a little "different". Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
That's great. When is the dual stator nacelle/hub kit coming out?  Central Victorian highlands |
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