From: "Jim Miller" 
To: ,
        
Reply-To: "Jim Miller" 


and that's why spider vanes made of wire have paired wires. it's much more
efficient to let a vane in another axis resist the twisting forces than
make an arbitrarily stiff vane do that work.

there are lots of examples on the net. www.jtmiller.com is mine for a
"three vane" wire spider. the 5" separation of the wires on
the hub prevents the twisting movement that would be seen by a
"vane" orthogonal to the wire pair.

have fun

jtm

----- Original Message -----
From: "Orion105" 
To: "'Jim Miller'" ; 
Sent: Thursday, February 20, 2003 9:08 AM Subject: RE: ATM Spider design
rules of thumb


In the limit, a spider "vane" could be a single wire; i.e. its
width would be zero.  This would not withstand the twisting movement I am
concerned with.

Ado



> -----Original Message-----
> From: Jim Miller [mailto:jim{at}jtmiller.com]
> Sent: Thursday, February 20, 2003 4:14 PM
> To: Orion105; atm{at}shore.net
> Subject: Re: ATM Spider design rules of thumb
>
> In spiders that I'm familiar with the "vane" are
> not responsible to restrain
> twisting since other vanes are resisting
> movement through tension that would
> otherwise be twisting the vane you are
> considering. You can use wires rather
> than vanes which are tensioned to provide the
> support. An offset four wire
> pair spider will offer the best support
> available.
>
> jtm
>
> ----- Original Message -----
> From: "Orion105" 
> To: 
> Sent: Thursday, February 20, 2003 4:15 AM
> Subject: ATM Spider design rules of thumb
>
>
>
> Are there any rules of thumb regarding the
> length to width ratio of
> spider vanes.  I see them made quite thin (10:1
> or higher) and quite
> thick (4:1 or so).  I guess you need width to
> stop rotation of the
> diagonal, but how much is optimum?
>
> I have seen spider vanes that taper in width
> markedly from the outside
> of the UTA to the hub.  I have even seen a
> design that goes the other
> way.  Is there any advantage in tapering?  It
> seems to me that
> resistance to twisting is proportional to the
> width of the vane and so a
> tapered vane would be only as good as its
> narrowest point.  Is this
> right?
>
> Ado
>
>

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