Go to Otherpower.com Home Page Go to Forcefield Shopping Cart Go to Wondermagnet.com Home Page
Front Page - [Homebrewed Electricity-- (wind) (solar) (hydro) (steam) (controls) (storage) (mechanical)] - Classifieds - Site News
Everything - Newbies - [Remote Living-- (housing) (heat) (light) (water)] - Rants & Opinion - Diaries - Our Products
First Genny,....up and running | 23 comments (23 topical, editorial)
Re: First Genny,....up and running (3.00 / 0) (#11)
by CmeBREW (smke833f@hotmail.com) on Fri Jul 25th, 2008 at 09:41:27 PM MST
(User Info)

I hate to reverse myself, but I just realized that was my OLD initial way of thinking when I said:

"However, to be honest, I worry about the 'stiction' problem pitching forward.  It Seems to me it would be MUCH less of a problem pitching backward. But I could be wrong."

I actually would rather choose FORWARD pitching for numerous reasons as Flux and others have said. I've seen numerous commercial mills pitch forward, so it must have advantages.  
-Hope your design works out well!



Re: First Genny,....up and running (3.00 / 0) (#17)
by CmeBREW (smke833f@hotmail.com) on Sun Jul 27th, 2008 at 07:30:10 PM MST
(User Info)

Interesting. I think I see now.  So, starting at anything much more than 5+ degrees would be a big, slow drag.  It would turn slow like a water pumper until a bigger wind finally came along to turn it backward momentarily to a decent angle, then it would go back to a slower drag in a short time.

I was sorta thinking that a coarse 25 degree angle would help in start-offs and 'take-offs'. (getting to the point of cut-in)

But now I see that starting at 4 or 5 degree (blades almost straight up and down) as the other's say would allow the prop to 'coast' (keep spinning a decent rpm) very well when the small wind breezes go down to almost nothing.  Which is what you want for low wind performance.

I did not know that at zero degrees the blades can keep going. That is good to know.

So the backward pitching goes from the 'normal set starting point' of 4 or 5 degrees to, say, NEGETIVE 5 degrees to basically 'air brake' when a big wind gust comes.

I am thinking of trying to do this for my small 6 footer. (but at a 700rpm or so since it is small)  

- I had one small observation though--

I could be wrong, but I was looking at where the blade pitch axis is on his blades (up near the top upper side of each blade), and it seems to me that that placement would be more suitable for blades that pitch to feather forward.
Could that axis placement actually counter resist pitching backwards??
I would've probably put the pitch axis a little BELOW the center of the blade to pitch backwards easier.  (maybe I'm looking at it backwards?/ It turns Counterclockwise right?)

 

[ Parent ]



Re: First Genny,....up and running (3.00 / 0) (#18)
by TomW on Sun Jul 27th, 2008 at 08:30:04 PM MST
(User Info)

CME;

It even gets more "fun" when you discover terms like apparent wind. Suddenly your pitch isn't really relative to the true wind. And its constantly changing.

In order to get a grip on prop pitch I had to think in terms of screw threads. a fine pitch takes more turns on a screw to go into the material than a coarse pitch. The wind being the "material" a prop screws through. Finer pitch on prop [more flat] lets it rotate more times and faster for a given "length" of wind.

Not very refined but helps keep it strate for me.

Tom

"Education consists mainly of what we have unlearned."--Mark Twain
[ Parent ]



Re: First Genny,....up and running (3.00 / 0) (#19)
by rpcancun (hobbyshopmx@hotmail.com) on Sun Jul 27th, 2008 at 10:07:21 PM MST
(User Info)

Yes youre correct I placed the spar one third the way back,...so the wind is pushing it to feather, that was done as a kinda failsafe if the springs broke or softened the wind would try to feather the blades so it can run wild,...i have to take down the blades and do some adjusting ill get ya some pics...

Thx

Rob

[ Parent ]



First Genny,....up and running | 23 comments (23 topical, 0 editorial)

Menu
· create account
· How to use the board
· FAQs
· search the board
· Google search the board
· Old Otherpower Board

Login
Make a new account
Username:
Password:

Powered by Scoop
You must be a registered user to post here. It's easy and free, and the link is on the upper right side of your page.
All trademarks and copyrights on this page are owned by their respective companies. Postings are owned by the poster, but may be deleted or moved at the ADMIN's sole discretion. The Rest © 2003 Forcefield.
You can Email the board ADMIN here. PLEASE include the username you signed up with!