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bigkat
Starting Member
USA
15 Posts |
 Posted - 22/03/2008 : 18:23:31
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well... I got it up... and the motor is not going to work... I am only getting 5v at full windspeed... but I got a rig ready for a motor that works...
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gotwind
Forum Admin
United Kingdom
754 Posts |
Posted - 22/03/2008 : 19:17:24
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Good start bigkat.
Those treadmill motors do take more revs to reach cut in than the Ametek generaly.
If you have good wind in your location, you could try shortening each blade by 6".
Alternativly use it as a 6v battery charger. The tail fin shows your creative ability, but should be a little bigger in area in my oppinion.
Keep up the good work, and keep us all posted please.
Ben. |
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bigkat
Starting Member
USA
15 Posts |
Posted - 22/03/2008 : 19:31:19
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thanks for the response gotwind... I am wondering if I could re wind the motor???
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gotwind
Forum Admin
United Kingdom
754 Posts |
Posted - 22/03/2008 : 19:36:31
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I wouldn't advise it, I know Fungus rewound an Ametek motor a few weeks ago.
I haven't heard the results yet, but it is a lot of work.
You are better getting an Ametek 30v DC motor - try eBay.
Ben.
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MattM
New Member
USA
84 Posts |
Posted - 22/03/2008 : 20:40:29
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You are losing some potential in the center. One constant I noticed when toying with blade shapes was that the interior of the blade made a difference in how ultimately fast it can rotate. The closer you can get to the center the faster rpm's seem to be possible. Wider blades at the extreme make a blade more sensitive to wind but the tradeoff is that as it spins faster the blades quickly stall and you reach a premature top end speed. The material is also going to have to support the weight of the blade and more material out from the center is more stress on the blade. By keeping the meat close to the center you raise the potential at the top end of the spectrum. Right now you have one sweet spot in the blade and virtually nothing to garner wind force at the origin and tips. Don't throw out what you have now, you can just move the holes out from where they are now and reduce the length from the inner diameter of the blade accordingly. And remember a sharpened leading edge is not a bad thing.
Ultimately the best blade will draw consistent force across the entire length. But when using pipe like you are doing it will pay off to keep the blade widest near the origin and taper to nothing at the tips.
Go Huskers! |
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bigkat
Starting Member
USA
15 Posts |
Posted - 23/03/2008 : 03:59:38
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Thank you for the input MattM... I will make the corrections when I replace the motor...
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keithw2112
Junior Member
United Kingdom
103 Posts |
Posted - 23/03/2008 : 14:26:00
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hi ya bigkat
well done with the genny looks great for a first attempt i started with a treadmill motor allways seemed to be spinning but hardly ever reached charging voltage switched to the ametek and regurley see 12v plus. looks a pretty good open spot perched on a hill by the looks
anyway dont give up keep trying |
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ghurd
Junior Member
USA
271 Posts |
Posted - 23/03/2008 : 16:02:56
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The inner 1/3rd of the blade only makes about 10% of the power.
It looks like the outer 40% are 'flat' to the wind.
Do they cup into the wind the same as the more center portions?
Maybe consider getting Ben's blade plans.
G-
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bigkat
Starting Member
USA
15 Posts |
Posted - 23/03/2008 : 18:01:07
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ghurd... I snapped a couple of pics to show you... the tips are about 2" in width... with a little cupping...
keith-
oh man... I have a perfect perch on a hill... one day I hope to have atleast 5 ginnys... and should be able to get off the grind with the power portion... :)
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bigkat
Starting Member
USA
15 Posts |
Posted - 23/03/2008 : 18:18:01
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here is a little video that I made also... kinda sucks you can't really tell how fast the blades are moving but it will give you an idea...
http://www.youtube.com/watch?v=wZ3l1kkA9P4 |
Edited by - bigkat on 23/03/2008 19:49:18 |
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MattM
New Member
USA
84 Posts |
Posted - 23/03/2008 : 18:27:01
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Your end of Kentucky looks a lot like my side of Nebraska, along the river. I always think of the Appalachians when I think of Kentucky. Is the state really indicative of your pictures or is that a relatively flat area?
Go Huskers! |
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bigkat
Starting Member
USA
15 Posts |
Posted - 23/03/2008 : 18:42:57
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MattM- I live in what would be call lower highlands of kentucky... the point of when it starts to move from rolling hill to mountains(and I use that term very loosely) because kentucky doesn't start to get real mountains for another maybe 35 or so miles east... but the western side of the state is pretty flat... but I am proud of being a hillbilly!!! :)
I live in Harrison Co... so this will give you a good idea where I live...
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ghurd
Junior Member
USA
271 Posts |
Posted - 24/03/2008 : 02:13:09
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That's what I figured. Sorry. The blades are no good.
The good news is the motor will probably work.
OK. Break the blades in 2 sections. Fat part and thin part. I'll deal with 1 section at a time.
You understand how the wind catches the wide part, making it turn. Simple.
The thin part has no reason to turn one way or the other. Meaning it is not helping.
It is the fastest moving part, and that means it has a lot of drag. It is holding the working part of the blade back.
And it gets worse. In a strong wind, the blade is bent from the frontal force, and the thin section is twisted in the wrong direction. Not only is it dragging in the air, but the faster the wind, the more drag the thin area is making.
The trailing edge (the long straight cut) needs to be in a straight line with the blade bolts.
Also, the most force will be at the flywheel. No reason to make that a narrow weak spot.
G-
A simple sketch I made for someone else years ago. He had the same problem.
This fixed him up...
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bigkat
Starting Member
USA
15 Posts |
Posted - 24/03/2008 : 03:21:51
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righton ghurd... that makes alot of sense... I will try to re-work my blades... but I had a set on there that kinda look like that design... but they're not as wide as that one...
I still only get 5v... so I think that motor is just not going to work...
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MattM
New Member
USA
84 Posts |
Posted - 24/03/2008 : 04:14:11
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Ghurd's example is a good compromise between simplicity and ease of duplication. When you work with pvc it just doesn't pay off to get fancy.
Be sure to check out Gotwind's visitors' pages that have a lot of pvc ideas: http://www.gotwind.org/visitor_1.htm
Air-X is a good example of what you can do if you want to get fancy: 
The blade in this case is not actually fixed in pitch, I am alluding to the general tapering. Air-X uses a nosecone on their turbines, which is why the blade has the thin flange to mount with, otherwise it probably would be wide there, too. Notice how the blade shape's curve is not a straight line. The material is only so strong and so as the blade moves out from the center it tapers on an elliptical curve to the point where the thickness is relative consistent only the last few millimeter of its length. Like ghurd related in his picture, the red line in that case is where your pitch should be nil. The trailing edge in the latter Air-X example actually uses a trailing edge pitch, forming an fairly flat S-shape (ogee) if you look at it from the tip on in. Too bad your pvc is so thick of material that it is not realistic to attach a downward curving trailing edge extension. The blades also thin down in camber as you move from center to tip, another unrealistic expectation for pvc. Camber (front-to-back thickness of the blade) is the least of your worries when working with pvc, because it is virtually nothing in your case. Again, the Air-X is a pretty damn fine blade if one wants to get real fancy.
Go Huskers! |
Edited by - MattM on 24/03/2008 04:35:06 |
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ghurd
Junior Member
USA
271 Posts |
Posted - 24/03/2008 : 04:18:49
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That sketch was just to show the trailing edge, related to the bolts related to the flat area of the hub. Seemed easier than words to explain it. Do Not imply anything into the proportions of that sketch.
Proportions are vital. As is length. It changes with every use. Everything is a balancing act.
Rounding the leading (curved) edge helps. Sharpening the trailing edge helps too (at least for noise).
Might buy a set of Ben's blade plans. Dandy place to start, and may work perfect as they are.
G- |
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new pictures of my windturbine...
