[ATM] Re: Second Thoughts on Mirror Support

[mdholm at telerama.com (Mark Holm)]

Well, I know it is the modulus that is needed here, not the strength.  I 
can't vouch for the numbers at the web site.

I really ought to convert all the units to metric and do the problem 
that way.  Then I wouldn't have the problem of pound force vs pound mass 
to add trouble.  (Don't want to smack into Mars!)

Mark Holm

Michael Lindner wrote:

>On Wednesday 04 February 2004 10:17 pm, Mark Holm wrote:
>
>>For small amounts of compression, compressive
>>modulus is often pretty close to tensile modulus, so it is probably safe
>>to  use that number, which is  89.9 ksi  Which means 89900psi.
>>
>
>Hmmm...then I think something's fishy. If I use a compressive modulus of 
>89.9kpsi, then I need a force of 103 pounds just to compress that silicone 
>pad 0.007". That seems excessive, as I think plopping 100 pounds on a 1" 
>diameter silicone pad would do more than compress it by 1/150".  Of course I 
>could be wrong...I'm not that familiar with these constants...
>
>Clear skies.
>