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First Genny,....up and running
By rpcancun, Section Wind Posted on Fri Jul 25th, 2008 at 05:36:38 PM MST
:)

Well it's finally up, not much wind to test though,.. after 100' plus of 12 gauge wire from tower to shop there was a good voltage drop,.. I was reading 6-8v in low wind after rectifier, but it does turn very slow, blades are for test puposes only and are on pith control and they are 1 foot wide by 6 foot long, with the pitch hub its around 14,foot diameter
Rotors are 14" 1/2 steel 12 2x2x1/2 mags per disk, coils are 16g 180 turns.
(9) coils,...if i where to go 16g two in hand would that mean to get the same volts it would be half the turns (90)?
Thx
Rob

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

Re: First Genny,....up and running (3.00 / 0) (#1)
by christopher on Fri Jul 25th, 2008 at 12:48:00 PM MST
(User Info)

no for the same volts you would need the same number of turns,but that would make the coils twice as thick.I would first look at the blades they look to wide at the tips and to much angle for any speed.

Re: First Genny,....up and running (3.00 / 0) (#2)
by Flux on Fri Jul 25th, 2008 at 12:55:53 PM MST
(User Info)

Those blades look more suited to a water pumper. The pitch looks to be nearly 45 deg. the tsr will be not much over 2.

You will have no starting trouble with no iron in the alternator, drop the pitch down to 5 deg or less and try again.

Two in hand will only let you use 90 turns and you will need to run it twice as fast to get the same volts.

Sort the blades out, don't go messing with the alternator at this stage.

Flux

Re: First Genny,....up and running (3.00 / 0) (#3)
by Flux on Fri Jul 25th, 2008 at 12:58:53 PM MST
(User Info)

Forgot to mention that there will be no volt drop on the line below cut in. You have that one to face if you ever get it over 12v.

Flux

[ Parent ]

Re: First Genny,....up and running (3.00 / 0) (#4)
by TomW on Fri Jul 25th, 2008 at 01:01:40 PM MST
(User Info)

rp;

Well, this makes 3 of us who think your prop needs more work before the alternator.

Awful coarse pitch to see any speed and you need speed.

Could be the photo angles too but thats how it appears from here.

Glad to see you got it flying even if it needs a bit of tweaking.

Good luck with it.

Tom

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

Re: First Genny,....up and running (3.00 / 0) (#5)
by rpcancun (hobbyshopmx@hotmail.com) on Fri Jul 25th, 2008 at 01:38:29 PM MST
(User Info)

Ok thx guys yes its at 45 degrees, better slow than too fast i can repitch them very easily,...i just need a couple freinds to bring it down.. ok so we will try them at what 30 degrees?

Thx

Rob

[ Parent ]

Re: First Genny,....up and running (3.00 / 0) (#6)
by Flux on Fri Jul 25th, 2008 at 01:43:13 PM MST
(User Info)

Try 5 deg, that is more in the sort of range you need.

Flux

[ Parent ]

Re: First Genny,....up and running (3.00 / 0) (#7)
by rpcancun (hobbyshopmx@hotmail.com) on Fri Jul 25th, 2008 at 01:47:21 PM MST
(User Info)

Hmm ok...maybe i did it backwards its starts at 45 but as speed increases it will reduce pitch all the way to 0,...so should I start it at 5 and have it increase pitch with speed?

Thx

Rob

[ Parent ]

Re: First Genny,....up and running (3.00 / 0) (#8)
by roadranger (Road Ranger at G Mail dot com) on Fri Jul 25th, 2008 at 01:57:01 PM MST
(User Info)

Yep - you got it backwards :-)

[ Parent ]

Re: First Genny,....up and running (3.00 / 0) (#9)
by rpcancun (hobbyshopmx@hotmail.com) on Fri Jul 25th, 2008 at 04:09:21 PM MST
(User Info)

I got it very backawrds its starts at 45 but as it goes faster it goes all the way to 90 (I had my 0 degrees wrong in my head) 90 degrees is like a feathered prop on a multiengine plane minimum drag, thats kinda what i wanted so if there was any heavy wind the blades would cut right thru..

Time to readjust and see....ill try 5 deg like flux says.....

thx

Rob

[ Parent ]

Re: First Genny,....up and running (3.00 / 0) (#14)
by MattM on Sun Jul 27th, 2008 at 01:01:21 PM MST
(User Info)

I thought 9º was closer to the pitch you wanted. I've played with various angles from 45º all the way down to 15º and can honestly say less is more in the case of a wind turbine. But 5º sounds awfully little even for a relatively low chord blade such as his.
----------------------------- Go Huskers!
[ Parent ]

Re: First Genny,....up and running (3.00 / 0) (#15)
by ghurd on Sun Jul 27th, 2008 at 02:13:59 PM MST
(User Info)

Many people think 5 degrees is awfully large.

You should start looking up the definitions of some of the big words before disseminating more bad information. Again.

[ Parent ]

Re: First Genny,....up and running (3.00 / 0) (#16)
by TomW on Sun Jul 27th, 2008 at 03:08:54 PM MST
(User Info)

G;

You should start looking up the definitions of some of the big words before disseminating more bad information. Again.

Good point!

Tom

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

Re: First Genny,....up and running (3.00 / 0) (#10)
by CmeBREW (smke833f@hotmail.com) on Fri Jul 25th, 2008 at 08:09:03 PM MST
(User Info)

Wow, that looks really good Rpcancun! Very professional looking.
A 16 footer with variable pitch-- talk about ambitious!
It is interesting and somewhat unusual.

It is my understanding that with variable pitch blades you can design it to go EITHER direction with the pitching. You can pitch forward ,or like you did, you can pitch the blades backward all the way to straight up and down which is what I always called zero degrees like you do. It seems to me it would be easier to design the pitching to go back like yours does instead of forward, BUT Flux and others have told me in the past that pitching Forward is more reliable for controlling in high winds and less 'Tower loading'. (Stress on the pole/tower)

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.

Perhaps you could start at less of an agressive angle-- like perhaps 25 degrees. It just makes me wonder if it isn't getting somewhat stuck at 45 degrees or so in very low wind, and it can't turn fast enough to begin to furl back (pitch) toward the steeper angles to really get going???

Can you tell us if you used the common method with 'Arm Weights' in order to pitch the blades using gravity as the rpm increases,, or did you use something different like your 'slide mechanism pitching'?
Can you quess what the fastest rpm it has acheived so far in the winds??

I was also wondering:
Did you purposely WANT to make a big, slower (visually 'controlled and safe looking')mill? And is this why you chose to make the variable pitch control blades?
Or did you do this because you thought it would make more power in lower winds?
Was it simply "Looks"?
It makes me curious as to why you chose this design and method of control.

- Very good work. Thanks for showing us your progress with pictures.
-Sorry for so many questions. It is just very interesting to me.

Re: First Genny,....up and running (3.00 / 0) (#12)
by rpcancun (hobbyshopmx@hotmail.com) on Sat Jul 26th, 2008 at 01:01:54 PM MST
(User Info)

Thx...

Yes i built it to be a slow machine,..I use to live in palm springs Ca.
and we have huge windfarms...they all turned very slow and slow = less vibration, noise, damage etc.
at least thats my 2 cents...

as far as variable pitch ive had that idea for more than 10 years
maybe finally i can get it to work....its a very simple design using the blades as counter weights with centrifugal force, im trying to make it as failsafe as possible...

i made a model its here in the board somewhere its exactly how i made the mill,...but its kinda fun testing this thing out it has its flaws but this is just a prototype thats why the blades are just flat plywood, the nice fiberglass blades come later when i get some more info on what is needed maybe tapered for more speed like flux and tom w have mentioned...its a work in progress....

as far as pitching what ill probably end up doing is have it start at 5 degrees and as it speeds up, have the pitch go to 0 placing the bottom of the blades into the wind (which is more stress on the tower and blades)
right now they pitch from about 5 degrees and as they go faster the pitch increases,...(less stress on the tower and blades) it's all trial and error now...

Thx

Rob

[ Parent ]

Re: First Genny,....up and running (3.00 / 0) (#13)
by Flux on Sat Jul 26th, 2008 at 02:03:10 PM MST
(User Info)

Slow is nice, but it is relative. Tsr6 or lower is probably something you can regard as slow especially with the common scheme where you go towards stall at full load.

Those commercial machines are likely to be faster than this, but because of the large diameter the rotational speed will be low.

Going much lower than tsr5 makes the alternator big and costly and the blade solidity rises rapidly and stress may not fall much.

If you pitch to stall I doubt that going to 0 will be sufficient unless you have a large stalling load from the alternator. Most blades will run well at 0 but may not start well. I suspect you may need to go negative, but the angular movement is way less than pitching to feather.

Flux

[ Parent ]

Re: First Genny,....up and running (3.00 / 0) (#20)
by rpcancun (hobbyshopmx@hotmail.com) on Mon Jul 28th, 2008 at 07:59:56 PM MST
(User Info)

Well theres some more pics...it's binding a little where the nut presses onto the spring,...i think i may need a bearing there but lets see how this works, after re adjusting and greasing everything the pitch bounced back pretty well, the good thing about using threaded rod is that i can reverse the blades very easy, gonna make some lighter airfoiled blades next after i see how it behaves,....what kinda taper would you guys recommend?

I wanted to stay with straight angles so i was thinkin maybe at 1/3 the way down taper to 6".....

Thx

Rob

[ Parent ]

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 ]

Re: First Genny,....up and running (3.00 / 0) (#21)
by small time on Wed Jul 30th, 2008 at 09:07:07 PM MST
(User Info)

I WAS LOOKING AT YOUR DESIGN AND WAS THINKING HOW DO U KEEP THE PITCH THE SAME FOR BOTH PROPS IS THERE SOME THING I MISSSED? IT SEMS LIKE THE ONE ROUNDING THE BOTTOM WILL HAVE MORE G FORCE AND IN TURN PITCH MORE VS. THE TOP? JUST A THOUGHT.

Re: First Genny,....up and running (3.00 / 0) (#22)
by Tritium on Wed Jul 30th, 2008 at 09:40:08 PM MST
(User Info)

Small Time,

No need to yell. (all caps is considered yelling)

Thurmond

[ Parent ]

Re: First Genny,....up and running (3.00 / 0) (#23)
by rpcancun (hobbyshopmx@hotmail.com) on Thu Jul 31st, 2008 at 12:12:13 AM MST
(User Info)

prop pitch was independent of each other, because i was shooting for low rpm so I wasnt to worried about it,..now it seems I may have to tie them together,....I have some ideas...

Thx

Rob

[ Parent ]

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

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