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Forum Index : Windmills : Help the FNG out
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| AndyL Newbie  Joined: 27/02/2012 Location: CanadaPosts: 3 |
G'day folks 
I must say, after a couple weeks of lurking, I really like this board compared to many of the others... Hopefully you guys can put up with another Frikin New Guy
We just bought our first house, it's in a good position for solar and wind - bald arse prairie right to my front door. Environment canada says 16mph (7ish m/s) annual wind average; winter closer to double that - summer has minimal wind. Category 3 by those other charts. Local utility rules allow grid tie-in with little fuss... Looking to more or less just build one and do it right the first time; PMA doesn't seem right - so I've ordered Hugh Piggott's book... Wondering when it might finally arrive... 
Going to limit myself a bit, <40' tower, 6' diameter, would love to see 1000w - but ok with half that... Question is largely - anyone want to help me work through the numbers? Magnet sizing, wire sizing, winding type, etc - Would like to start ordering up some of these parts, and start drawing things up (while I'm in town with access to the hackerspace's CNC Laser - which makes things much faster - I'm terrible with wood) Question 2 - blade design... Now, having access to a CNC router, and 3D printers, and really - it'd be a simple job to throw together a CNC foam cutter based on the RCZone designs (I've done enough work with composites, and have all the stuff for vacuum bagging). Seems strange to hand carve blades - when I could computer cut them doesn't it? I've seen all kinds of designs - but pretty much all meant for hand carving... Is there an optimized blade design floating around that I can't find in google? Thanks in advance! |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Andy I would use Hugh's book as a bible. Build your first turbine as laid out in the book, and I'll guarantee the process will answer most of the questions and doubts you now have. After that, you'll have a better understanding of what to modify and how it may affect the windmill. I've been down the path of CNC'ing foam blades. Yes its accurate, but very time consuming. Have a look at the chain saw article Oz put together http://www.thebackshed.com/Windmill/articles/ChainsawBlades. asp. At the end of the day, the chain saw made blades will work 95% as good as a set of CNC made blades, but for less money and time. Another option is the GEO222 profile blades, available here in Oz as PVC or Aluminium extrusion, in North America as carved timber blades from Royal Fabrication. These dont spin as fast as the Hugh style carved blades, but offer better low rpm and startup torque. It depends on the alternator and load, but you'll understand the relationship in time. Welcome to the site. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| AndyL Newbie Joined: 27/02/2012 Location: CanadaPosts: 3 |
Yeah I'm just kicking myself for ordering a real book and not a download now :) As it's now onto it's second week waiting to clear customs...  Just wanting to get on with parts ordering so it's not july by the time I can get her finished...
I've looked at the chainsaw blade cut - that's what got me thinking CNC... :) And the more I read on hand carving them, the more I think about machining em... |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
The biggest hurdle with hand/chainsaw made blades it letting go of perfection. Like a lot of people who have used CNC in the past, we know we can build 100 parts that are perfect within 0.1mm of eachother. So when we think about making a set of turbine blades, we expect the same accuracy, but realise we cant achieve that with hand tools, so we look at other options, like buying factory made blades or using CNC. But the fact is, we dont need to be that accurate. A set of 2 meter blades, as in Oz's article, can have differences of several mm, but this wont have any noticable effect on turbine performance. Lumps and bumps dont matter, so long as the blades are the same length within a few mm, follow the same line within a few mm, and same angle within a couple of degree. It's OK if the profile is slightly different between blades, even weight isn't a problem, we can add weight to balance the turbne once assembled. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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