RE: [ATM] Use of bearings in (static) mirror cells

["Jerry Reddell" <jerry.p.reddell63@sbcglobal.net>]

I am sure there are forces acting perpendicular to the mirror face IF the
silicone is glued to the mirror edge and IF any movement of the mirror
occurs along the axis. In my opinion, collimination should be independent of
the mirror back and side support system ( In other words the collimation
moves the mirror, side supports, and back supports as a unit so that no
relative motion occurs.). Otherwise don't glue the mirror edge to the
silicone.  Perhaps other, slicker yet elastic materials could be found that
would work better.

Either way, without realistic analysis (simulation)which include the
silicone/material properties and sizes, I am skeptical that properly
implemented glued silicone imparts forces sufficient to cause objectionable
mirror distortion.

Jerry Reddell



-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net]On Behalf
Of Koehler, Steve
Sent: Monday, April 25, 2005 2:02 PM
To: atm@atmlist.net
Subject: RE: [ATM] Use of bearings in (static) mirror cells


Jerry,

> Personally, I like the idea of a cylinder surrounding the mirror with
> silicone inside between the mirror and the cylinder.

One thing I haven't seen mentioned in this discussion is the need to keep
edge
supports from acting perpendicular to the mirror face.  I'm not sure your
silicone edge support would do this very well.

For example, if you collimate by raising or lowering one or more of the back
support pads (or pad groups), then the mirror must slide against the edge
supports without being held back.  (An alternative would be for the edge
support
and back support to be part of a solid unit that is adjusted together in
collimation.  However, then it is necessary to make sure that stresses don't
build up within the unit due to varying expansion factors of different
materials, etc.)

A sling does well at avoiding forces perpendicular to the mirror face, as
long
as it is kept parallel to the edge of the mirror all the way back to the
support
bolts.  Various alternatives exist for two-point edges supports, such as
using
roller bearings, or flexible piano wire studs.  Making the contact points
slippery with something like Teflon also helps.

-- Steve Koehler
   steve_koehler@securecomputing.com


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