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Forum Index : Windmills : Cogging: Floating hub solution?

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domwild
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Joined: 16/12/2005
Location: Australia
Posts: 873

Posted: 12:27am 08 Mar 2008

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Guru Michael Lawley (ecoinnovations) sells or used to sell F&P based mills using a floating hub (?) to get around cogging and this is my interpretation of what is meant by it (and I haven't got a clue!):

The F&P shaft is 25.0 mm and therefore fits a metric ball bearing very nicely. The imperial pipe size for the prop hub is 41.9 ID, so close to the 42mm required for the bearing (25x42x?). Have no lathe, so I filed it!

The prop then is attached to a flange connected to the pipe via a BSP thread, the pipe is supported by two bearings on the shaft. The prop is attached via two steel strips to the pipe flange. Blade is 1.5m radius to get the torque for an uncogged F&P.

The idea is to allow the prop to spin up without turning the rotor, then the hub should engage with the F&P shaft somehow. This was achieved via a bolt hitting a spring-loaded hinge.

It works if there is a separation of the bolt from the hinge, which in the best case is one rev or 360 degrees. The worst case is direct contact (0 deg.) and the wind slowly winding up the spring leading to repeated turning and stopping of the rotor on the shaft.

The spring should absorb any shocks from star/delta switching or gentle/full braking. I may not use any furling and chose instead to use electronically driven braking as PVC props IMHO stall anyway and do not overspeed. The breaking is used to reduce the load on the tower during gales.

The testing is nowhere complete, there are only two PVC blades (bad!) instead of three, the tower was only a three meter (10') effort and there is "she who must be obeyed" and demands a restoration of the house and not playing with my mill! But do not hesitate to comment on it; this method is called a floating hub, I suspect and is not a product of my overly fertile imagination.

I may have to keep you in suspenders for a while as a photo will follow unless i am prompted after pressing "Post" for an attachment. I will learn, have patience!

Regards,

Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up.

Winston Churchill

domwild
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Joined: 16/12/2005
Location: Australia
Posts: 873

Posted: 12:46am 08 Mar 2008

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Friends,

As I do not have my own webserver and therefore cannot give you a URL for the photos of the solution (?) but if you are interested in the photos, pls access the following:

Somehow get into my photo uploads of domwild at www.fieldlines.com and click on

hingespring.jpg

and others hanging around. Hope that helps.

Cheers,

Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up.

Winston Churchill

Gill

Senior Member

Joined: 11/11/2006
Location: Australia
Posts: 669

Posted: 04:33am 08 Mar 2008

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Dom,
Have tried to understand your design, but typical of academic descriptions that are perfectly clear to the describer, is confusing to the interpreter. So I could well be wrong in what I understand. A plan, sketch, circuit diagram or photo is of great help.

I cannot see how the prop will unwind back to the start position when stopping. Perhaps I have it wrong.

To add a photo you have, click the 2nd icon from the right (tree with up arrow) and follow the prompts. The usual hints of keep file size small and press [enter] for a new line between pics is also good.

or

Go to your pic on the other web site and 'copy' the address, come back to this one and press the tree icon (no up arrow), them 'paste' the address in the box.

or

Link to the pic on the other site by copying it's address as above, then coming back here and pressing the 'world & chain' icon. First box write a word like 'SEE HERE' next box paste the address.

Hope that's helped.

Edited by Gill 2008-03-09

was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ

Tinker

Guru

Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 02:28pm 08 Mar 2008

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Dom, the bolt idea gives you not enough spin up IMO.

How about the following idea I have seen used in some (not wind mill related) machinery.

Find a suitable clock spring and attach the inner end to the shaft and your floating hub to the outer end.

With no wind the spring will unwind the floating hub. Wind will start turning the propeller and in turn start winding up the spring. This can be many full turns, depending on your spring. As the spring gets wound tighter the magnet rotor starts turning gradually and couple fully when the spring is wound up completely.

You could try those springs used in pedestal drills to return the spindle, they're pretty tough.

Mind, I have not tried that idea, perhaps somebody here will shoot it to pieces

Tinker

Klaus

brucedownunder2
Guru

Joined: 14/09/2005
Location: Australia
Posts: 1548

Posted: 08:28pm 08 Mar 2008

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Philm has done this.

Maybe you ask him to explain his idea,I've seen it --It works just perfect ,think he uses a fine spring off a brush cutter or something.
after the mill stops it "rewinds" and comes to rest,then when the wind blows ,it it spins up ,engages, and whammo , away it goes.

Bruce

Bushboy

KiwiJohn
Guru

Joined: 01/12/2005
Location: New Zealand
Posts: 691

Posted: 07:19pm 09 Mar 2008

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Maybe a 'Bendix' mechanism from an old starter motor could be used? They were on some cars and trucks where the pinion was mounted on a helix so that when the motor started the pinion was thrown into mesh with the ring gear. Might be on some modern vehicles too for all I know.

You could put the helix on the shaft and fit the pinion to the turbine hub. Use your light spring to wind the turbine backwards to one end of the travel then when the wind starts I think there would be a couple of turns until the pinion hit the end of its travel and started turning the genny.

domwild
Guru

Joined: 16/12/2005
Location: Australia
Posts: 873

Posted: 10:18pm 09 Mar 2008

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Friends,

Thanks for all the suggestions. And thanks to Gill to explain to me how to ad pics on this forum. This is my first attempt.

The problem for me is that without a lathe or better workshop I cannot build anything sophisticated.

Regards,

Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up.

Winston Churchill

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