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bike hubs

07/22/2007 2:31 AM

I need some explanation and diagrams on bike hubs: freehubs, internal gear hubs, whatever you have.

I am planning to use them to have a variable speed drive on a windmill.

Check these other questions to understand the situation:

Redesigning windmills to use screw pumps

How to design a screw pump?

Is there any way to make them switch automatically?

I want my system to maximize the torque when the wind blows at less than 10 km/h and to minimize it when it is over 40 km/h.

I think I can use something similar to bike hubs to control the drive from the floor, at the base of the windmill, with a cable.

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#1

Re: bike hubs

07/22/2007 6:34 PM

Hi Gussosa - A small type of auto transmission might do. or you may consider a fluid drive. With cost being an issue you may have to look at a V belt pulleys where the pitch can be adjusted while running. it is made of 2 halves where the distance between the halves are increased or reduced. The traction of a belt is on the side.

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#5
In reply to #1

Re: bike hubs

07/23/2007 2:52 PM

That is simular to the old Bridgeport milling machine, if you incorperated a governer like the old steam engines, this could be used to control the pulley halves thus controlling to a certain degree the output shaft!

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#2

Re: bike hubs

07/23/2007 6:57 AM

IMHO-

using actual bike parts would not be a good idea.....not built to handle the torque needed to drive a generator with a usable output.

However, if you have machining capabilities, you could probably copy the ideas behind the bike systems and build beefier units. Look into Sturmey-Archer multi-speed hubs.

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#6
In reply to #2

Re: bike hubs

07/23/2007 4:03 PM

That's exactly what was in my mind when posting this question.

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#3

Re: bike hubs

07/23/2007 9:40 AM

Simply not enough infos given.

What sort of generator are you looking at? AC or DC?

What Voltage output? 12volt, 24volt 48volt 110volt 220volts or what?

How many watts maximum?

What speed does the generator need to be turned at to achieve its correct output?

What speed will your windmill turn at when at the bottom and top of its wind speed ranges?

Will you have any control over the angle that the windmill blades have to achieve some speed/power control?

Are you (and your neighbours!) prepared to accept the noise levels made when generating in a good wind? It will be even worse if a gearbox is turned as well......

Have you made plans on what to do with the dead birds as they get hit by the blades?

What about the damaged humans if it is not mounted high enough? (the noise will be propagated further, the higher you have it. The best winds are higher than most houses......)

Make sure you design a fool proof method to turn it out of the wind, stop it and hold it stopped for maintenance & repair....and when you want to sleep.....!

I am sure that I have not asked all the needed questions, but it is a start.....

I personally feel that a gearbox of any sort, is an unacceptable extra load that needs to be turned = loss of efficiency.

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#7
In reply to #3

Re: bike hubs

07/23/2007 4:05 PM

This is not an airgenerator, it is an airpump. This a windmill used to pump water.

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#4

Re: bike hubs

07/23/2007 1:42 PM

Bike hubs are NOT the way to go. As an ex-bike racer and a mechanical engineer (see the avatar), bike hubs are designed for a pure vertical load with very little allowance for a side load. (For the purists, yes there is a side load while turning or going though a curve, but the primary loading is vertical. As for power loading, a bike racer can put out a consistent 350 watts (about 1/3 horsepower). (I hear the engineers and cyclists screaming at this one.) Still, the maximum load is about 1 horsepower which would be suitable for a windmill that would likely be suitable only for a small household. If you ran an air-conditioner and washing machine you may not be able to even run light a bulb. A refrigerator and air-conditioner would be out of the question.

Graham Obree used washing machine bearings for his record-setting 1 hour bike ride. The relevance is that a person on a bike can put out just about the power of a washing machine. Any more power would probably destroy the bike parts.

Competitive Go-Kart parts would be in about the right power range, but the racing transmissions may be too pricey.

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#8

Re: bike hubs

07/23/2007 5:07 PM

Especially because you want an "automatic" gear selector, you should look into Continuously variable transmissions. Especially the pulley type.

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#11
In reply to #8

Re: bike hubs

07/26/2007 11:48 AM

How do you automate a pulley transmission?

Sorry, but the only place where I had found info on transmissions is HowStuffWorks. There isn't any book on the subject in my uni's library.

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#12
In reply to #11

Re: bike hubs

07/26/2007 11:49 PM

I can't seem to find a good pic, what you are looking for is used on snowmobiles & scooters. centrifical weights & springs cause the drive [ as opposed to the driven ] pulley to shift, different weights & springs the "program" rate@ which the shift happens.

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#14
In reply to #11

Re: bike hubs

07/30/2007 12:15 PM

Here is a pic on HowStuffWorks. http://auto.howstuffworks.com/cvt2.htm

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#9

Re: bike hubs

07/24/2007 12:32 AM

You might consider variable pitch blade, similar to a helicopter.

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#10
In reply to #9

Re: bike hubs

07/24/2007 5:21 AM

This idea is similar to a proposal I made earlier, that the pitch is altered not a gearbox. Pitch has the possibility to change speed without placing extra loads onto the power source, just slightly more complicated if you do it well.....

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#13
In reply to #9

Re: bike hubs

07/27/2007 1:09 AM

It has been rolling around in the back of my mind for a while now, that a wide blade made of thin, flexible plastic, rigid only on its lead edge, could be designed (cheaply, I might add) that flexes relative to wind pressure, in effect creating a self-regulating, passive variable-pitch blade.

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#15

Re: bike hubs

03/14/2008 10:30 AM

Are you still working on this project? I recently saw a fan on a car that is used for drag racing. It had flexible blades that grab lots of air at low engine speeds. But flatten out as engine speed increases, lowering power consumption. Would this work in your application. These fans pull good air till about 2500 RPM. Then they pull regressively (?) less air up till over 6000 RPM. What speed will your turbine spin at?

Another thought. We purchased a fire truck with a hydraulic powered generator. The engine can run any speed between 600 and 2500 RPM, and the generator power remains constant. The engine turns a hydraulic pump and produces hydraulic power. This hydraulic power turns a hydraulic motor that turns an alternator that produces 60 hertz. This is accomplished by means of a variable speed and displacement hydraulic motor. With a wind speed generator creating a variable voltage signal, and that variable voltage signal used to vary the hydraulic motor's displacement, you should achieve your request all automatically. And all without an outside power source. www.harrisonhydragen.com is the site for the company. They have been doing this for over 20 years that I know of. Hydraulics are great when done correctly. Self lubricating as well. Check their site and think of the reduced complexity of the finished product. Good luck.

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#16
In reply to #15

Re: bike hubs

03/14/2008 1:48 PM

Hi Bob

I have abandoned this project for a while due to lack of funds but I thank you a lot for the ideas. I will keep you informed if I ever make it to make this design real. As far as I can immagine, the variable angle fan, the variable speed pulley and the hydraulic transmission are the only viable alternatives here.

Best wishes;

Gustavo

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Users who posted comments:

Andy Germany (2); bob c (1); charlie_r (1); Garthh (2); gussosa (4); Hendrik (1); Mr. Truman Brain (1); mrhippo2 (1); Munky (1); Thor (2)

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