[ATM] Whiffle Tree mirror edge support help needed

[kb7h at onemain.com (Ken Hunter)]

A "whiffle tree" is a device that equalizes and combines forces.

The classic example is the "DrawBar Whiffle Tree" used on teams of horses to
pull a wagon. These are always seen when the cowboy jumps between the horses
to stop them from running away with the pretty girl.

Another example more easily found is the arrangement of an automotive
windshield wiper where the forces along the blade are equalized by support
from a "Whiffle" arrangement.

Ken Hunter

----- Original Message -----
From: "Rapha?l Guinamard" <rguinamard@infonie.fr>
To: "The Amateur Telescope Makers List" <atm@atmlist.net>
Sent: Tuesday, February 24, 2004 2:39 AM
Subject: Re: [ATM] Whiffle Tree mirror edge support help needed


> I'm always confused about the term "whiffle tree" and I don't have
"whiffle"
> in my dictionnary.
> By "whiffle tree", do you speak about the arrangement of triangle/bar in a
> cell or about a type of edge support with no sling like piano wire or
> others.
> So what is whiffle tree?
> Rapha?l Guinamard
> ----- Original Message -----
> From: Mark Suchting <masuch@cia.com.au>
> To: Lawrence Sayre <lsayre@neo.rr.com>; The Amateur Telescope Makers List
> <atm@atmlist.net>
> Sent: Tuesday, February 24, 2004 9:29 AM
> Subject: Re: [ATM] Whiffle Tree mirror edge support help needed
>
>
> > At 07:56 PM 2/23/2004 -0500, Lawrence Sayre wrote:
> >
> >
> > >Can anyone point me to good examples of Whiffle Tree based mirror
cells?
> > >Sites containing pictures would be great
> >
> > Judging from your subject line, I take it you are asking about edge
> supports
> >
> > There is an example at:
> >
> > http://www.nightskyscopes.com/site/std_mirrorcell.shtml
> >
> > Click the small image of the edge support for a larger one.
> >
> > These manufacturers are using a layout favored by Pegasus optics for
> > testing large thin mirrors.  The fulcrums of the two wiffle-tree bars
are
> > at 60 degrees apart , and the pads on either end of each bar span 30
> degree
> > apart. This leaves 30 degree gap between the inner two pads . Adding
> > another four bars in this layout ( for an equatorial mounting layout )
> > would give 12 pads at 30 degree spacing, something which George Ritchey
> > seemed to favor in his famous essay.
> >
> > I've tested this layout with 20" X 1.6" with horizontal axis and the
> mirror
> > figure held very good.
> >
> > For edge support in the telescope I'm more in favor of the piano wire
edge
> > support at 90 degree because it works and is so simple to make . Have
> > tested these on a 16" X 1" thick mirror.  I don't see any good reason to
> > use slings anymore.  Theres not much practical information on the Piano
> > Wire supports on the WWW yet.   Check the archives,    also :
> >
> > http://www.astrosurf.com/altaz/lateralsupport.htm
> >
> > In truth these supports  can either be a `machinists wonder' or a short
> > length of 1.5mm piano wire poked into a wooden block with a little
teflon
> > pad on the end.
> >
> > Hope this helps.
> >
> > Mark Suchting
> >
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
>
>
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.593 / Virus Database: 376 - Release Date: 20/02/04
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/