Re: [ATM] PLOP Assumptions

[Dale Eason <atmpob@yahoo.com>]

Plop assumes the support pad is a point and it
calculates how the mirror will deform around that
point under gravity loading using finite element
analysis. This is based on the material properties of
the glass you choose.  Plop knows those properties and
so can calculate how much droop will happen.  It helps
you discover how many finite points and at what
positions you need to keep the deformation below a
threshold.  In general using small pads instead of
points is a very good approximation and will not
change the results in a bad way.

Dale Eason
--- artbianconi@blast.net wrote:

> I don't use PLOP.  I have reservations about the
> accuracy with 
> which any mechanical device can be built that
> responds in a 
> uniform and consistent manner to changes in force
> vectors. In a 
> car engine perhaps where things are relatively
> crude. But on a 
> mirror mount? 
> 
> In examining the few multi-point cells made
> available to me, I am 
> puzzled by the assumptions some are making in
> defining the size 
> and material used in the pressure pads.
> 
> It would appear that many ATM's are assuming that
> the pad is 
> distributing the force equally over it's entire area
> and the 
> coincident surface of the mirror. Is that
> reasonable?
> 
> Is PLOP assuming that the pressure pad is NOT
> bending under the 
> load and that the distributed loads are uniform?
> 
> Art Bianconi
> Milford, NJ
> 
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> 
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