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Forum Index : Windmills : Lenz2 angle
| Author | Message | ||||
| thefinis Regular Member  Joined: 23/08/2006 Location: United StatesPosts: 53 |
Well I finally got the big wings up and flying on the test tower. My question to those who have a set of these wings flying is this. On the first drawing of Lenz wings with the air deflector in the middle the angle was set above the 90 degree mark at around 80 degrees from perpendicular while the Lenz2 shows the angle below the 90 degree line at near 100 degrees. Was the angle set different because of the deflector or the chord size? Has anyone used different angles? Mine are set at 99 and it would be a real pain to try and change the angle now as I did not make them adjustable. I am having to redo the prony brake as the friction pad is too small for this set of wings but will post results when I have them. Pictures soon. Next project is a real tilt up tower with no climbing that gets above the trees. Finis Texas born and bred |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I used Ed's angles on mine. I know he did a heap of testing to get the best angle, so I'll take his word for it. I put some adjustment in mine, + or - 5 degrees, but found his angle of 99 degrees worked the best. I also tried a 2 wind design and that seamed to work better, but was slightly harder to start and the torque pulses were bad. Ed said he tried the 2 blade and also had slightly better results, so is continuing his research. I thing your 99 degree will be fine. Cant wait to see the pics, how is it performing? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| thefinis Regular Member Joined: 23/08/2006 Location: United StatesPosts: 53 |
I used Ed's angle too but after it was up and spinning I went back over all my files checking and found the angle differences. I know he changed the angle as the wings developed but wasn't sure if it was due to size or altering the configuration. What worried me most was that one was set above 90 at about the same amount as the later one was set below 90. The test tower is in a really bad location for wind but is close to the house and tools for easy blade building. One of the things that keeps biting me in the rear is torque x rpms = power. Big diameter large winged vawts have really low rpms and must make it up in torque. It becomes hugely important to keep low rpms as high as possible because each rev carries so much energy. Makes me want to build a hawt except for furling, turning to face the wind and no real ability to stack turbines. Here are a few pics still no power readings. Hopefully soon will get a chance to redo equipment for some figures. The dark tape is to repair where calves bit the foam board silly critters. Finis 
Texas born and bred |
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windstuffnow Newbie  Joined: 30/06/2006 Location: United StatesPosts: 31 |
Looks good finis, can't wait to hear some output specs on it. It's definately going to have alot of torque! On the angles, here is a diagram that should help clarify the scale and angle... 
Overall, I've found its quite forgiving between 0 and 15 degrees but the best performance is at 9 degrees ( 99 degrees as measured from the back ). |
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| thefinis Regular Member Joined: 23/08/2006 Location: United StatesPosts: 53 |
Thanks Ed you sent me this diagram before so it is in my files. It was when I compared it to the orignal lenz drawing that I got worried. Finis Texas born and bred |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I like the look of that windmill you got there Finis. I could watch that go around all day. Well done. The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| thefinis Regular Member Joined: 23/08/2006 Location: United StatesPosts: 53 |
Hmmm I had not heard/seen that a 2 wing version did better. I could make this like an S rotor with 3(2 wing) layers staggered which should smooth the pulses out like a 3 wing. It would take more supports and extra ends but should take less total material. May have to make a small model and see how it stacks. The wings I have up now have a few quirks from Ed's pattern. I am not sure if the diameter should be taken for id or od. If id then the curve/cup diameter is a little smaller than wanted. The flat section of the wing is about 2-3 cm longer than it should be(2 percent). At the back edge of the wing is a piece of 1.5 inch(3.75 cm) black plastic pipe cut in half that(I hope) acts like a small flap/bump aprox 1.5 cm high. With my luck it will create drag instead of lift. After I get some readings with it this way I change it to a flat piece and try again. Seeing 20 mph winds gusts even in the trees today and center support is flexing when wind above 15 mph. That is not good. I hope I can design a strong enough support setup for these. Some of it may be misadjustment of the trailing edge cables. Tried again to use the friction brake lever but wings won and ate the rubber bushing. Was seeing 20 ft lbs at 28-30 rpm and barely slowing the wings down before the bushing went completely. Wind was around 14-17 mph. Getting some hard pulses and loading/slowing it down did not seem to help. Seems to occur at about 120-180 degrees from dead on to the wind at about the time the curve/bucket quits catching the wind and the flat backside is catching wind but not making power/lift. Finis Texas born and bred |
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