Notes on SHARP mechanical design

Based on discussions on Dec. 8 between Jeff, Thang, Hua-bai, and Giles

The modular design includes four boxes.  We discuss the design of box 1
(the lowest box) here.  Some of the others will be slightly different, but
the design principles will be the same.

For box 1 the top and bottom must hold optics so need to be precisely
constructed, and the top needs to be located precisely with respect to the
bottom.  This will be done by using vertical posts and also diagonal
struts (see figure 1).  The diagonal strut functionality will in reality
be incorporated into "side panels" that will mostly be open (see figures 2
and 3).

Bottom, sides and top will be approx 0.160" thick.

Bottom should perhaps be even thicker?

Top will be thinned to 0.050" over most of the surface and will have holes
to pass beams as specified by Hua-bai.

Sides will be mostly empty (see figure 3) and will have have threaded
holes for attaching very thin "panels" (.020") that will be painted on the
inside or alternatively may have plastic absorbing squares fixed to the
inside.

Posts will be approx. 0.625" square.  

Note that in figure 2 the posts are drawn to the same thickness as the
sides.  In reality the posts will be thicker. (~.625" vs. .160")

Location of dowell pins TBD.