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Forum Index : Other Stuff : Building a Prony brake
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Well I've just about given up testing my windmills in the wind, cause I dont have any wind here. My neighbor has good wind, in fact every one else in my neighborhood has good wind, I can see their trees blowing about. My tree's dont move. "You got a dirty great hill blocking your wind mate" I've been told. So, until I move to a better place, I'm going to do bench testing only. I needed a Prony brake, so I can accurately measure power and efficiency. Add a couple of meters and I would be able to plot power/RPM/voltage curves. I used a DC 130v treadmill motor and controller. This is the result. 
The pulley on the F&P shaft was from the treadmill, I found it didnt give enough reduction in RPM, so I ended up using a spare F&P hub as a large pulley. 
Heres a closer look at the bearing. 
Tomorrow I'll calibrate the thing, work out some bearing losses, and start testing. I have some batteries so I can test for 12/24 and 48 volts, I can experiment with the cap conversions, and test my staggered stators to work out the cut in speeds of each stage. Jolly good fun 
Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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sPuDd Senior Member  Joined: 10/07/2007 Location: AustraliaPosts: 251 |
These might help you with your wind deficiency Gizmo: 
sPuDd.. It should work ...in theory |
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fillm Guru  Joined: 10/02/2007 Location: AustraliaPosts: 730 |
The utilux clip bearing housing , that is a classic Glenn  . You might find that the scales are very hard to see the small differences in power , Big w has cheap digital scales and they zero at the touch of a button. Good to see the results when its up and going PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
[quote=Phill]You might find that the scales are very hard to see the small differences in power , Big w has cheap digital scales[/quote] In my experiments with a De Pronybrake/dynamometer on the lathe, I too used analog kitchen scales. The pointer moved wildly during tests, one had to average by eye the reading. This is easy to do with analog scales, but impossible with digital scales, where the numbers jump rapidly around but one can't see trends or averages. This is one case where analog, despite its (perceived) lower accuracy, is better than digital. Peter. |
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Perry Senior Member Joined: 19/11/2009 Location: Posts: 190 |
Have you had any luck with this? I am interested in doing the same. I also have the unlucky distinction of a wind turbine hobby in a location that has no wind. I feel your pain. Perry |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Perry I had a problem with the belt slipping if I tried to draw any mor ethan 200 watts from the F&P. If I increased the belt tension, the F&P hub I was using as a pulley would deform. So I took the hub into a mates workshop and machined some groves to match the multigrove belt I was using. 
Thats as far as I got. I havn't had a chance to try it out, but I will in the future. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Dingdoc Regular Member  Joined: 23/09/2009 Location: AustraliaPosts: 76 |
Hi Glenn Have you considered using a magnetic damper on the end of the torsion arm to stabilize your readings on the scales? It would be pretty easy to add with just an aluminium vane between a couple of strong magnets. Trev |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Thats a good idea Trev. I have a bunch of hard drive magnets that will work perfect. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Perry Senior Member Joined: 19/11/2009 Location: Posts: 190 |
Have you thought of using the 2 fish scales and a belt method? It is usually what I think about when I envision a prony brake. It seems like it would be more forgiving of the various 'bump' readings a spring scale might experience. Perry |
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