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Forum Index : Windmills : Newbie Furling revisited

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WineGuy

Newbie

Joined: 16/04/2008
Location: United States
Posts: 10
Posted: 11:39pm 15 Apr 2008
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Newbie question here:
I'm in the process of building my first wind gen. I plan on creating a plate to mount one of the three different DC motors I have, so I can experiment with blade and tail designs.

I plan on using the furling design and calculations from this site (nice site by the way), but have a few "generic" questions. The answers need to be generic because I don't have ONE windmill, I'm going to use the plate to try out three different windmills.

Specifics:
Generators are between 4 and 8 inches diameter and between 10 and 15 inches long, 4 to 10 lbs in weight.
One of them is an Ametek

Planning on using a 2" post for the top of the tower.

Two bearings and a coupler between the gen and the blades to reduce thrust force on the gen bearings.

Using 4 foot diameter PVC blades for the first trial.


Please remember these questions are from a first timer.
The design is using a plate with a furling tail, mounted on a post.
I am looking for thoughts as opposed to actual numbers.

1) For the purpose of balance, should the post go closer to the blades or the tail, or center of the generator? I know this mostly depends on the relative weight of the blade vs the tail, but it sounds like a good question.

2) Similar question for the other axis. Assuming the edge of the generator is "near" the post, how much of an offset to the tail pivot should be used? Once again a "rule of thumb" answer is good.

3) The design page calculations references 20 degree and 45 degree angles but the pics don't show which is which.
Is the 45 with respect to the horizontal, or with respect to the generator axis?

3) I'm assuming the top of the pole should be approximately one foot above the base of the generator? Is this a good assumption?

Any thoughts greatfully appreciated.

Sure wish I was smart instead of so darn cute!
 
Gill

Senior Member

Joined: 11/11/2006
Location: Australia
Posts: 669
Posted: 12:33pm 16 Apr 2008
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G'day WineGuy,
Here's how I see it, but remember I'm just an old bloke so please don't beat me up if I get too technical.

1) The positioning of the generator is not a matter of balance as the tail weight and length makes it heavier that end. Select your overhang to allow for max blade flexing from the strongest winds. You indicate use of PVC blades so as these have a goodly amount of flex, mount your motor/prop well forward, in addition to this, do like the huge wind generator people do and put a 3 or 4 degree tilt back on your mounting platform to give the blades added clearance.

2)Too much offset needs a very long and/or heavy tail. Not good. Keep it close. For a 4ft dia prop, I'd reckon about 2" at most.

3) The 45deg is in respect to the generator axis, the 20deg is to off vertical.

4) 1ft above? Why? If it is serving some purpose in the design, then whatever it needs. As a general rule of thumb, I try to keep everything as low as possible. The less weight up your pole the better. Also guy wires cannot support higher than the lowest swing of the blades so the lower you can fit tail mountings etc. the less moment of force on the tower. Styling by the girlfriend may override these design considerations however.

Gee I love giving long-winded answers. I hope that's done the trick?

Good luck with your project.

Gill edit: sorry I misread your question 2. I commented on prop shaft offset where you said tail offset. Sorry. There is no need for any tail offset at all, but if your design needs one then that is no problem either.Edited by Gill 2008-04-17
was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
 
WineGuy

Newbie

Joined: 16/04/2008
Location: United States
Posts: 10
Posted: 01:10pm 16 Apr 2008
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Thanks for the info, now for the followup.
I'm going to try to sound intelligent here, so please bear with me.

The 20 degree down angle is so the tail returns to the "home" position. 20 degrees does not seem like a lot of angle. I would have guessed this to be the 45 degree measurement. Doesn't the tail "flop around" excessively with this small angle?

The 45 degree with respect to the gen axis angle; I assume that this is to keep the tail from crashing into the blades when it furls, correct? Question becomes, how do you make a tail that goes straight back when you have to mount it to a plate that is on a 45 degree angle?

Any thoughts would be appreciated.


Sure wish I was smart instead of so darn cute!
 
woofnumber0
Newbie

Joined: 26/04/2008
Location: United Kingdom
Posts: 10
Posted: 08:00pm 25 Apr 2008
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Hey i read so much maths on these forums.setting angles the easy way .my method hinge the tail with bearings top or bottom or any other method.Fit a sat jack arm dangle the wire down wait for a good wind.test current, or say hey mibbye thats sping kinda.and ajust the dangle.WOOFO
 
woofnumber0
Newbie

Joined: 26/04/2008
Location: United Kingdom
Posts: 10
Posted: 11:58am 26 Apr 2008
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The tail fin im on about,NOT THE ARM
 
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