Subject: George Mount,Acquisition Cam and Flexure Issues
From: "Vern Stahlberger" <[email-masked]>
To: "George Koenig" <[email-masked]>, <[email-masked]>
Cc: "Douglas Toomey" <[email-masked]>, "Vern Stahlberger" <[email-masked]>
Date: Tue, 7 Oct 2003 10:49:14 -1000

Hi,

To get an idea for the structural stiffness of the George Mount
a simulation was done.

A jpg showing the results of the FEA is attached. (georgefea01.jpg)

FEA Model Setup:

1) The Load was taken to be 160 lbs and is acting in the z-direction.
(see triad in jpg.) The load is due to the Acquisition Camera and its
contents, in addition to the large X-Y Stage. This is a worst case scenario,
the case where the telescope would be horizontal.

2) The mounting surface that in practice bolts the George Mount to the
AO Spool, is held fixed in the Simulation Model.

FEA Results:
 
The maximum displacement seen in the FEA Model is .0021 inch
with a top stress of 1540 lbs/in^2

I recall a number .013 inch that George measured. It appears that the George
Mount is not wholly responsible for the flexure. Where does the rest of the
flexure come from? 
The  stiffness of the Structure that holds the POM was analyzed when the 
Acquisition Camera was built. Deformations were found to less than .001 inch.
In this case, a 10 lbs load was assumed for the POM.

Further Comments:

The structures were analyzed not using any bolted joints. If the bolts in the real
structures are not fully tightened, flexures are the result.

A further area to check is the POM and its mounting. Did anything change?

Has this flexure been seen when the Acquisition Camera was in place? Has it
been measured the same way?

Vern