From: "Tom Krajci" 
To: 
Reply-To: "Tom Krajci" 


From: "Nils Olof Carlin" 

>...To make a good support, I
>believe you need to handle forces in two planes or directions
>simultaneously and independently...

From a conceptual standpoint using two separate methods of mirror support
for the two planes (perpendicular and parallel to the mirror's face) sounds
easy...but two questions:

A.  Do astatic lever support systems use an edge support as well?

B.  What about edge supports for slumped blanks?

>Using the same support points for the two sets of forces has obviously
>worked well enough for you....

Yes, that's because it turns out I was really not pushing the envelope very
much, if at all.

>but predicting the perrmance and the deormations
>to expect may be more difficult yet.....

One of these days I hope we get some sort of analytical tool in the hand of
amateurs to address this problem.

>In conclusion, the edge support seems to deserve far more attention
than
>It generally gets AFAIK, but there are no doubt workable solutions to
>preserve the potential performance of a very well figured mirror. But
I'd >like to have more background, and a better understanding of the
potential >pitfalls, before I'm prepared to accept the assumed superiority of the
>RTV-ed cell.

Based on comments from Ray Desmaris, when he made a very large, thin,
slumped mirror...he used RTV for his attachment method...and no slings.
(However, he made a mirror that was not diffraction limited...which was not
called for in this particular job offer...but Ray seemed convinced that
slings or other edge supports would not work as well as his RTV donut
method.)

See: http://astro.umsystem.edu/atm/ARCHIVES/MAR03/msg00030.html

>One could perhaps start by examining the elastic properties of RTV
blobs, >and go from there to see what forces can result?

Can anyone point me to some data on the modulus of elasticity, poisson's
ratio, etc. for cured RTV silicone adhesive?

Thanks in advance.

Tom Krajci
Tashkent, Uzbekistan


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