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Show ALL Forums  > Science/philosophy  > A question about windmills      Home login  
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 caffeinejag
Joined: 1/7/2006
Msg: 1
A question about windmillsPage 1 of 2    (1, 2)
In the typical horizontal windmill why only three blades?

Just remember all the old windmills in the westerns had like 20 blades.

I know that in the very large windmills the blades are quite long and this means that the tip of the blade has to be travling at a very high rate increasing the stress on the blade. This also means that the blades have to be made to withstand this stress. Would more blades of smaller length provide as much torque as the standard large three blades?

Just curious.
 aaamm
Joined: 7/5/2009
Msg: 2
A question about windmills
Posted: 12/25/2009 8:27:18 PM
Don Quixote successfully killed the ones with more.
 endlesslift
Joined: 12/31/2009
Msg: 3
A question about windmills
Posted: 1/3/2010 10:36:48 PM
Yes, it's just the cost and strength of materials that influences the number of blades.

You get different number for different size and types of windmills though. Different materials, different purposes and all that stuff.

Dutch windmills have lots of blades and the big commercial ones come out with three.

I worked on designing a small one and I looked at a 4 blade to simplify hub construction and cut costs.
 LeCutter
Joined: 2/25/2009
Msg: 4
A question about windmills
Posted: 1/6/2010 5:47:28 PM

Don Quixote successfully killed the ones with more.


Don Quixote exists to remind us of both the futility, and nobility, of tilting at windmills. The Don is one of my heroes.

This is my fave print, Lyceum Don Quixote ....

http://www.art.com/products/p10029378-sa-i788530/william-james-nicholso-lyceum-don-quixote.htm
 *Starstuff*
Joined: 11/6/2009
Msg: 5
A question about windmills
Posted: 1/7/2010 6:27:48 PM
My favorite Quixote is Picasso's version.
 aaamm
Joined: 7/5/2009
Msg: 6
A question about windmills
Posted: 1/7/2010 6:38:00 PM
^^^^^Is that the one of just his head? I should Google it.

Lyceum Don Quixote is nice because it does have the windmill in the picture.

I had a couple carved wood figures of Don and Sancho. But, sigh, I decided to part with them as I have also parted with all my books about Don.

Holland Michigan has a few windmills, but they don't have the solar ones last time I visited there.
 yna6
Joined: 1/21/2007
Msg: 7
A question about windmills
Posted: 1/8/2010 9:06:57 AM
Why do they build windmills with only three blades? As with almost ANY question of "why don't they....?" the answer is money!
It is cheaper to build them like that, and still have them perform up to expectations. Adding more blades adds more costs, but does not proportionately increase the windmills efficiency. Therefore, a cost analysis would show that a three bladed construct would be the most economically viable.
 coveredinpaint
Joined: 7/13/2009
Msg: 8
A question about windmills
Posted: 1/8/2010 9:27:01 AM
I think the blades are longer in order to provide more leverage to turn the turbine. And there are probably only three due to weight/balancing issues.
 endlesslift
Joined: 12/31/2009
Msg: 9
A question about windmills
Posted: 1/8/2010 11:14:39 AM
Actually the longer blades work well because the outer part is moving very fast.
 xlr8ingmargo
Joined: 7/28/2009
Msg: 10
A question about windmills
Posted: 1/8/2010 11:45:10 AM
Longer outer parts moving faster?
Man my brain just went into the gutter but there wasn't any room left...
Gotta be me.
 xlr8ingmargo
Joined: 7/28/2009
Msg: 11
A question about windmills
Posted: 1/8/2010 2:18:07 PM
I've learned a lot off these threads.
As far as the latter part of your post it depends on what kind of mood I'm in!
Longer is always better...
 endlesslift
Joined: 12/31/2009
Msg: 12
A question about windmills
Posted: 1/10/2010 10:56:51 PM
windmills have mood?
 nipoleon
Joined: 12/27/2005
Msg: 13
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History
A question about windmills
Posted: 1/11/2010 2:19:57 AM

Longer is always better...

When asked how long a man's legs should be ?...
Abraham Lincoln answered, " Long enough to reach the ground ".
 xlr8ingmargo
Joined: 7/28/2009
Msg: 14
A question about windmills
Posted: 1/11/2010 3:27:51 AM
No just chicks that can blow (maybe enough air to make a wind mill function, or should I say fukction). Extended "blades" that reach optimized performance levels are always an asset especially if they can reach the ground (well maybe not).
Windmills are awesome when you look at them through my eyes.
 endlesslift
Joined: 12/31/2009
Msg: 15
A question about windmills
Posted: 1/13/2010 12:03:00 PM
I am interested in creating an open source windmill design.

I was figuring if it were made out of common materials that would be cool.

I was thinking that an egg beater type would be a good choice. Also I was thinking of 4 blades to simplify the hub assembly.
esentially
Any ideas?
 scorpiomover
Joined: 4/19/2007
Msg: 16
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History
A question about windmills
Posted: 1/13/2010 12:44:35 PM

In the typical horizontal windmill why only three blades?

Just remember all the old windmills in the westerns had like 20 blades.

For a horizontal windmill the number of blades may vary between one and forty. Mills for power generation normally have two or three; mills for pumping water require more.
http://web.me.com/paulscott.info/maths-of/windmill/howmany.html

The graph indicates that the amount of power generated increases with the number of blades, but only slightly. So the benefits of that increased power must be balanced against the increased costs of the extra blades and a stronger supporting framework.
http://web.me.com/paulscott.info/maths-of/windmill/howmany.html

In the old days, people were short of resources, but had plenty of time, and these windmills were their major source of power. So they took longer to make a windmill, but built it to last, and so it could handle the extra blades.

These days, windmills are made primarily to make money, by collecting energy and selling it to consumers. So the main objective is to start making money as soon as possible, by getting up as many windmills up as soon as possible. In addition, because they are commercial ventures, they are mass-produced. Odds on, some will fail, but the minority. So it's cheaper to put up 1000 cheap windmills and then have 50 fail, rather than put up 500 sturdy windmills that cost twice as much, and then have none fail. You've effectively gained the money from another 450 windmills. A cheaper windmill has a less sturdy framework, and cannot support quite as many blades. But you don't gain anywhere near as much in greater power from a sturdy windmill as you would from just building more of them. So, you build more of them. Lots of windmills might be a blot on the landscape. But you're in it for the money. So who cares?
 LeCutter
Joined: 2/25/2009
Msg: 17
A question about windmills
Posted: 1/13/2010 11:51:24 PM
Remember doing the health-hustle in school? Windmilling one's arms and such? They always told us it was good for us. Yet, I question if the damage to the rotators was offset by the excercise and preventing arthritis.
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