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DaViD

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Joined: 14/01/2009
Location: United States
Posts: 120

Posted: 05:08am 27 Mar 2009

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Actually that would only be 100 microns differance on each side of the shaft which would be really ideal for a grease packed bearing. Any less play would probally cause excessive friction and scarring of the pipe?

If your not living on the edge your taking up to much space!

montyLalor

Newbie

Joined: 17/12/2008
Location: Australia
Posts: 21

Posted: 06:30am 27 Mar 2009

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Okay, time for my first post. I've been lurking around reading all I can from all you Learned Ones for about three months now.

The prompting for my response is the fact that these blades are a perfect candidate for the self-feathering hub I've been designing in my spare time.

It'll take me at least two generations of 3d solid modelling before I machine a prototype (my first concept weighs about 10kgs! but is just to get the fundamentals down pat first).

Thanks Janne for the input regarding off-the-shelf bearings in a previous hub of yours. I had pondered the wisdom of using roller/taper bearings as blade feathering mounts. I might investigate plain bearings or something like a phosphur-bronze bush set as an option for my next cad model.

I'd say as a rough guestimate, that I'd need to get the hub down to a weight of about 4-5kgs so that I had a 2.5m diameter assembly weight of about ten kilos.

Anyway enough rambling. I have hair to pull out and monitors to swear at. (It's called drafting.)

Nice work Gizmo on sorting the blade's supply. A few month's hard work finally paying off. Gold.

I can't say when I'll be needing a couple of blade lengths, but I will need 'em. Christmas is my loose goal at the moment.

Luke

"So are you doin' this project to make us money or cost us money?" she asks again...

oztules

Guru

Joined: 26/07/2007
Location: Australia
Posts: 1686

Posted: 12:25pm 27 Mar 2009

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Janne,

Using the entire 22mm rod length (maybe 800mm long) up the inside of the outer (exhaust tube) is perfect for the Jacobs application. Most time is spent fully locked "in", and when it does turn, it slides as well. It is the best journal/system for this kind of thing. Some slop is necessary to allow air to move out of the cavity, and not act as a piston when it moves in and out (and around). It need only be an agricultural fit..... even excessive slop won't effect this system markedly.

The big / massive return springs keep the slop biased both radially and planar, and provided the spider is using good ball joints, I can't see any degradation to the system from sloppy exhaust/rod unions

.........oztules

Village idiot...or... just another hack out of his depth

Janne
Senior Member

Joined: 20/06/2008
Location: Finland
Posts: 121

Posted: 12:55pm 27 Mar 2009

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Hi oztules,

I didn't realize it was the jacobs pitch system that was thought in here

Though i don't have any experience with that kind of pitch mechanism, it would seem likely that the rod&pipe bearing should be good, like you stated. The spring neatly also takes care of the centrifugal load of the blades, which imho is the nr. 1 killer on "normal" pitch control hubs.

heh, agricultural fit, does it include an installation with 20lb hammer too? ;)

If at first you don't succeed, try again.

My projects

Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5119

Posted: 06:34pm 28 Mar 2009

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Well they are flying.

I'll write up the build in my diary tonight. This is a dual stator F&P windmill with staggered connections and a 2.7m diameter tubine. The winds are very light today but its started a few times and I've see a couple of amps so far. I've set the blades at 5 degrees.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

DaViD

Senior Member

Joined: 14/01/2009
Location: United States
Posts: 120

Posted: 04:06am 29 Mar 2009

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Looks really good! I know you said winds were light but did you notice
any flexion of them?

If your not living on the edge your taking up to much space!

GWatPE

Senior Member

Joined: 01/09/2006
Location: Australia
Posts: 2127

Posted: 11:40am 29 Mar 2009

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I am surprised there is no twist yet. Maybe on the next set. Is there much distortion of the section when twisted? Have you felt how much effort is requires to twist the blade? The tiplets add a distinctive look.

Looking pretty neat so far.

Gordon.

become more energy aware

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5119

Posted: 12:21pm 29 Mar 2009

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No twist on this set. All I had was a hair dryer and it didn't have enough heat. Besides this profile has a wide angle of attack and I'm starting to think twisting would only give a tiny gain in performance. On the Windcharger windmills they use this same profile with no twist either. I will buy a heat gun and try twisting a smaller diameter set in the next few weeks. This set was just to see how easily I could put a turbine together.
No flexing, the exhaust tube up the middle makes these very rigid.

I've started a diary on the build.
http://www.thebackshed.com/windmill/forum1/forum_posts.asp?T ID=1657&PN=1

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

niall1

Senior Member

Joined: 20/11/2008
Location: Ireland
Posts: 331

Posted: 01:17pm 29 Mar 2009

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hi Gizmo

only noticed now from the pics that your winglets are down wind ... sweet , good luck with the testing

Edited by niall1 2009-03-30

niall

SparWeb

Senior Member

Joined: 17/04/2008
Location: Canada
Posts: 196

Posted: 07:37am 31 Mar 2009

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How about twisting the blade before fastening it to the pipe? To have consistency you need a kind of lever that rotates one end and holds it as you drill the holes, etc., but as you put in screws/rivets you end up with a fixed twist in all blades. Of course if you tried it yourself in your hands and found that there could be kinking or warping then why bother...

Have you flown that F&P with other blades before?

Steven T. Fahey

DaViD

Senior Member

Joined: 14/01/2009
Location: United States
Posts: 120

Posted: 11:22am 31 Mar 2009

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Hi Glenn, We stripped some paint off of a pipe bollard cover made with PVC using a heat gun and it made it really brittle so be careful when heating them.

If your not living on the edge your taking up to much space!

Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5119

Posted: 10:18pm 31 Mar 2009

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Quote Have you flown that F&P with other blades before?

Yes, this was part of my 6 blade windmill put together in 2007 http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?T ID=744&PN=1
It worked good until it threw a blade a few months ago.

I plan to done some testing with twisting in the next couple of weeks.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

SparWeb

Senior Member

Joined: 17/04/2008
Location: Canada
Posts: 196

Posted: 06:05am 01 Apr 2009

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[quote=Gizmo]I plan to do some testing with twisting [/quote]

...DROOL...

Steven T. Fahey

gabbro
Newbie

Joined: 14/06/2007
Location: Australia
Posts: 4

Posted: 11:32am 09 Apr 2009

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Hi all,

As these blades have no twist does that mean they would lend themselves equally well to VAWTs? Or do VAWTs require a different shaped aerofoil altogether?

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5119

Posted: 12:49pm 09 Apr 2009

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Hi gabbro

I've had emails from Wes ( the man behind these blades ) asking the same question. Short answer, yes they would work. The curve in this profile means they would work for a Darrius/H rotor with a diameter of 500mm to 800mm. A larger diameter would need a flatter profile, which could be achieved by heating these blades on a flat surface ( BBQ? )

Couple of links about profiles used for larger diameter lift type verticals.
http://users.xplornet.com/~rmanzer/windmill/mzr-2_design.htm l
http://www.anotherpower.com/gallery/airfoils/naca_0012
http://purrfectcatshelter.org:8080/James/darrius/

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

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