Thanks George. When I heard about this hinge I originally envisioned "two 
crossed wires" in two round rings... and no matter how I spun those rings 
around in my head I could get them to work as a hinge.  Now that you have 
explained it, I understand-- It is the same type of hinge that is commonly 
used on model airplanes for the vertical and horizontal rudders.

Thanks-- Steve PSN San Jose,  Aptos Calif.

-----Original Message-----
From:	George Harris [SMTP:gjharris@..............
Sent:	Saturday, November 23, 2002 4:37 PM
To:	psn-l@..............
Subject:	Re: Another horizontal boom/mast pivot to consider

From George Harris:

The Fletcher type joint is probably similar to the one which consists of
two round elements connected by flat tapes in such a way that the tapes
cross in an "X" between the rollers.  The joint has the unusual combination
of no friction, and no torque due to the fact that as one tape unrolls, the
other
end rolls up so there is no net energy used in bending the tapes.  The 
tapes
must be intension (obviously I guess), but their thickness is not important
as long as they are working within the elastic limit.

----- Original Message -----
From: "steve hammond" 
To: 
Sent: Saturday, November 23, 2002 8:28 AM
Subject: RE: Another horizontal boom/mast pivot to consider


> I'm looking for info or a drawing of a Fletcher joint and that may not be
> the correct spelling of Fletcher. It is a joint with two rings and two
> cross wires and has zero friction.
> Thanks --
> Regards, Steve Hammond
>
> -----Original Message-----
> From: meredithlamb [SMTP:meredithlamb@..............
> Sent: Friday, November 22, 2002 10:00 PM
> To: psn-l@..............
> Subject: Re: Another horizontal boom/mast pivot to consider
>
> Hi all,
>
> I read plus's and minus's into this topic.....ball v/s torsion pivots.
>
> Perhaps a part of the aspect of a torsion pivot is that it likely is a
> type of somewhat unstable double pivot pendum in essense, one
> at the top (of the mast) and the lower torsion wires flexible movement
> itself.  There is a name for such, but a brief search engine search
> yielded nothing for the moment.
>
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