Author Topic: Chain Gear Drive PMA  (Read 3213 times)

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Yianie123.

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Chain Gear Drive PMA
« on: May 04, 2015, 02:01:15 PM »
I am sure this asked been asked a million times, but has anyone used gears and a drive chain to drive a PMA?  Lets say that you have a 16:1 or 20:1 where for every 1 rotation of the blade you have 20 rotations of the PMA.  The blades would have to be large but due to friction losses, it may actually move slower, but with more power.  Any opinions, photos, comments will be greatly appreciated.

Mary B

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Re: Chain Gear Drive PMA
« Reply #1 on: May 05, 2015, 02:17:20 AM »
Yes one of the members here made a ferrite magnet PMA that is chain driven. Chris Olsen...

Flux

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Re: Chain Gear Drive PMA
« Reply #2 on: May 05, 2015, 04:17:40 AM »
In low wind areas, a prop with higher solidity may work slightly better than a fast low solidity one but this is marginal and in normal winds a 3 blade prop with tsr from 4 to 7 usually gives the best results and has a much lower thrust on the tower. As this type of prop suits direct drive up to at least 17ft diameter it is the most commonly used. All transmissions have losses so it is hard to beat direct drive in the region where it is practical.

In the early days all commercial size turbines were forced to use some form of gearing, but even those now have reverted to direct drive.

If you are in a marginal wind area, where things are not strictly viable ( average wind speed below 7mph) you may find a benefit from a higher solidity prop with more than 3 blades and a direct drive alternator becomes big and costly and a small ratio speed increase with a chain drive could help. I would only consider a chain, not belts or gears, and to get any efficiency and life out of it the chain needs to be enclosed.

Mary B mentioned the chain drive alternators used by Chris Olsen. Chris was using ferrite magnets and for the same speed a ferrite alternator will be about 4 times the size of a neo one. By doubling the speed this lets him use a much smaller and efficient alternator. It does in this case make sense but remember that Chris is a first class mechanical engineer with all the design knowledge and facilities to build a reliable and efficient chain drive.  To work it needs first class engineering and will not be cheap.

Most of the machines here are designed so that they are easy for home build with limited facilities, other options are certainly possible. The radial flux alternator is almost certainly better than most axial machines but doesn't lend itself to home build as it needs concentric parts and has no tolerance for design errors. If you get the turns wrong with an axial you can change the air gap, with a radial you rewind it.

When you mention large speed increases, yes they can be done, the old water pumper type mill with multi blade fan can produce electricity with a high ratio speed increase, but contra to your expectation the result will be very poor compared with a similar diameter 3 blade direct drive and will have large wind loading problems in high winds.

Many things are possible and in experienced hands may work fine, but the designs devised by Hugh Piggott and the Dans of this board have been perfected so as to be easy to build, give good performance and good reliability, I would stick to something similar as a first step into wind turbine building.

Flux

mbouwer

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Re: Chain Gear Drive PMA
« Reply #3 on: May 05, 2015, 07:02:04 AM »
Flux,

What do you think about avoiding neodymium?

Regards Rinus

Flux

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Re: Chain Gear Drive PMA
« Reply #4 on: May 05, 2015, 09:10:21 AM »
For damp or marine climates there is a good case for using ferrite unless you can find a satisfactory way to protect neos, especially in the open axial designs.

The ferrite alternator will be much larger and heavier, you will save on magnet cost but pay heavily for more copper. For direct charging the ferrite machine can be quite satisfactory at least in the sizes up to 8 to 10ft. , above that ferrite really needs a speed increasing transmission to compete. Again for mppt the speed increasing drive again becomes more attractive to get the full benefits.

Much depends on your ability or desire to get a much heavier alternator up in the air, once it is up weight is of no real consequence.

If you live in a climate where neos present no problem then they do have most of the advanatges.

Flux

mbouwer

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Re: Chain Gear Drive PMA
« Reply #5 on: May 05, 2015, 03:15:16 PM »
Flux,

Thank you for answering us.

There are so many possibilities to think about. For example what Enercon does.
They use electric exited magnets and they are very succesfull.

Rinus

Yianie123.

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Re: Chain Gear Drive PMA
« Reply #6 on: May 05, 2015, 03:45:08 PM »
Does anyone have any pics they can share of a chain drive PMA.

klsmurf

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Re: Chain Gear Drive PMA
« Reply #7 on: May 05, 2015, 04:02:00 PM »
The search engines on the forum are your friends.  :)
" A man's got to know his limitations " ------ Harry Callahan

Flux

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Re: Chain Gear Drive PMA
« Reply #8 on: May 05, 2015, 04:29:38 PM »
This link to Ed Lenz's site shows a very basic open chain drive, it may work fairly well in dry climates but for long life and decent efficiency a chain needs to run in an enclosed bath with reasonable lubrication.

http://www.windstuffnow.com/main/newpage5.htm

I suspect if you use a google search on the Fieldlines site you can find Chris Olsen's chain driven ferrite machines.

Flux

Mary B

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Re: Chain Gear Drive PMA
« Reply #9 on: May 05, 2015, 06:18:04 PM »
Some of Chris's build, I know he had a thread on building the transmission but I didn't do a deep goggle search for it. http://www.fieldlines.com/index.php/topic,146180.0.html