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super windy
Junior Member
195 Posts |
 Posted - 17/04/2008 : 20:29:28
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Hi everyone @gotwind, finally had a few hours today to assemble the blades and put them on a bycicle wheel bearings, the video shows it on a very turbulent wind, has it its the house then reflects back to the blades, so not ideal, anyway here's the video,(ghurd try and resist in not clicking on the video , I know you will though, and I actually need advice:http://www.youtube.com/watch?v=nSN1gfeVwkg
I am happy with the tracking I got that pretty sorted, however I had the whole thing pretty balanced but then applied another 2 coats of danish oil, and the balance went out of the window, I am using a old bycicle wheel bearing and its not tooo bad, but I reckon the bolt inside is slightly bent, ideally I would love to fit them to the alternator and then balance them but the alternator has a fair amount of cogging so no can't do, so I am back to the bycicle bearings, I did when I first assembled it put a string from the middle and raised it and added different weight so it was perfect but after another 2 coats of oil the balance is gonne I sort of kknew that it was going to happen has I could feel the different density of the 3 blades and I knew that somme would absorb the oil more than the others.
so to all the experienced wood blade builders what is the easiest and best way of balancing these I want them pretty good has I don't want the bearings on the alternator to fail.
anyway got to go
super windy
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gotwind
Forum Admin
United Kingdom
762 Posts |
Posted - 17/04/2008 : 20:51:59
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Cool.
I think the bicycle bearing maybe a bit too sensitive.
Maybe this is why the 2 coats of danish oil is appearing to effect the balance?, not having built a set of wooden blades myself I can't really comment more accuratly.
The siren in the background in the video is the 'gotwind safety police' looking for a mad man having too much fun with DIY wind turbines 
Ben.
The Futures Green - Getwind of it. |
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super windy
Junior Member
195 Posts |
Posted - 17/04/2008 : 21:52:06
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cheers ben, I think you are right the bearings are too sensitive I just want the balance to be spot on, so I don't bugger the bearings on the new alternator, also I have removed the shaft of the bycicle bearings and it is definatelly bent , bugger how am I ever going to get these blades balanced, I guess I will just travel to the nearest underground station and nick one of the back wheels of someone's bike.
I think you are right about the police, and hopefully they will take me because I'am definatelly losing my marbles, I drive around london looking for things to use for the generator, I guess I'm hooked, and there is no cure, it could be worse I guess.
cheerio
super windy |
Edited by - super windy on 17/04/2008 22:00:10 |
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gholt
Starting Member
USA
47 Posts |
Posted - 18/04/2008 : 04:05:09
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Hello SW,
Your latest video of your blades is impressive - as always.
Blade balancing need not be taxing and the following solution is fairly easy and straight forward.
You will need:
1. 1/4" doweling (6mm)
2. Bird shot (sportings good store or a shotgun shell from a hunter type friend)
3. Super glue (cyanoacrylic glue)
1. Obtain some doweling (1/4" [6mm])and cut 3 plugs of the same length - approx 1/4" [6mm].
2. Drill a hole (the same diameter as the doweling) in the big end of each of your blades to the same depth on each blade - perhaps 1 to 1.5 inches [25mm to 38mm].
2. Weigh each blade.
3. Add enough bird shot into the hole to make each blade the same weight as the heaviest blade.
4. Add two or three drops of super glue to the shot to keep them in place (carpenter's glue works just fine too).
5. Plug all three holes with the doweling plugs.
Remount the blades and check the balance. At this point, light surface sanding should be all that's needed to make very slight changes.
Personally, I'd use either epoxy resin and spar varnish (spar varnish is UV resistant) as my finish coat rather than danish oil ... but it's a tad late to tell you that now ... sorry.
I would also find some aluminum tape - the type used by heating and air conditioning workers - and apply it to the leading edge of the finished blades. This will help keep the blades from eroding in stormy (wind and rain) conditions. Fiberglassing the leading edges is also a good approach but needs to be done before any finish coats and your oil probably will not allow it at this point.
G. |
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super windy
Junior Member
195 Posts |
Posted - 18/04/2008 : 14:30:20
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cheers guys just finished balancing the blades, and they work a treat, I replaced the bycicle bearing with a drill chuck and was able to balance them better, I also went online and found this usefull:
How to Balance Wind Turbine Blades
Wind turbine blade balancing is actually a very simple process, but you must do it on a totally still day (i.e. no wind) or do it indoors. Pieces of lead flashing (used by roofers) work best as they are soft (easy to screw in place) and very dense. It can be obtained in flat sheets from a builder's merchant or you can use fishing weights can be hammered flat. Fix the blades onto the alternator in what you intend to be their final positions numbering each blade and the alternator accordingly so that you can take everything apart and put it back together again correctly in future.
Now gently spin the turbine and leave it too come to a complete stop. Whichever side is the heavier will finish at the bottom (6 o'clock position). Raise the heavy side up to the 3 o'clock position and add a weight on or near the hub at the 9 o'clock position (and more weights if necessary) until it balances - i.e. the weight(s) remain at the 9 o'clock position with the previous heavy side at the 3 o'clock. Gently spin the turbine a few more times. If it stops at the same point each time, then that is the new 'heavy side' and you need to repeat the steps listed above. Very quickly you will have a balanced wind turbine and you will not need to re-balance it again unless you replace a damaged turbine blade in the future.
An alternative way to balance wind turbine blades (pictured above) is with a weight and a tape measure. Spin the turbine around to get one of the blades in the horizontal position. Stop the turbine. Sit a weight on the blade as close to the hub as possible. Slowly move the weight outwards until it causes the turbine to rotate - measure this point. Repeat this with each of the blades of the wind turbine generator. If the three measurements are the same then the blades are all balanced. If however the measurement for one of the blades was greater, that blade is lighter and so a lead weight should be screwed to the alternator where the light blade connects to it.
A further way to balance wind turbine blades is to hang the blades and hub from its centre using very strong string. Add weights where necessary near to the hub until the blades all sit level.
hopefully this will help someone else.cheerio
super now balanced windy
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ghurd
Junior Member
USA
274 Posts |
Posted - 19/04/2008 : 03:17:31
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Nice! Glad they balanced.
G- |
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super windy
Junior Member
195 Posts |
Posted - 19/04/2008 : 16:59:17
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cheers ghurd, I will in due time do another little set for the ametek to see how they perform, but from what I can see the airfoil works much better than the pvc ones, although it is more work involved has I can now make a set of pvc blades in less than an hour, while the wooden ones will take me a good half day just to carve them, although with the right tools it becomes much easier, I used a recipricating saw to remove the large amount of material, then an electric planer to get close to the outlines, then a belt sander, excellent tool by the way, quick removal of material, ( I will give you a little tip with belt sanders, when the belt starts to get clogged up with debris get a garden hose put the sander on and run the end of the hose on the belt and right before your eyes you will have a clean belt that will last you forever.).
cheerio
super windy |
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ghurd
Junior Member
USA
274 Posts |
Posted - 19/04/2008 : 20:08:03
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Cheers SW,
And I'll give you a tip.
Wind blowing the dust around is a pain. It gets in the eyes and nose.
I make blades on that... what does my wife call it???
Ah, yes... I remember now...
She calls it "the kitchen table".
I am thinking about something the opposite of carved wood blades.
Maybe a 6 or 8 PVC blade, dia of 0.75 meter, on a PMA better suited to 400W?
A certain waste of materials, however it may be far better for the constraints I have to work within.
I have the bits now. I'll update everyone when I get time to build and test it.
G-
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super windy
Junior Member
195 Posts |
Posted - 20/04/2008 : 21:45:58
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Hi ghurd
I am also contemplating on making a hub with 5 pvc blades, maybe 750mm long, with a fair bit of torque for my new generator, I will use the wooden ones while In portugal, but here due to my location, maybe the pvc ones, just have to get the alternator now, everything else is ready.
cheerio
super windy |
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super windy
Junior Member
195 Posts |
Posted - 22/04/2008 : 16:15:07
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I finally managed to get the balance spot on, and changed the bycicle bearings to a old drill chuck it isn't soo sensitive but it works really nice.
cheerio
super windy |
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assembled wooden blades/little video
