From: mjc5{at}psu.edu
To: atm{at}shore.net
Reply-To: mjc5{at}psu.edu


At 10:05 AM -0700 8/20/03, Jon Bishop wrote:

>I like your idea of using superballs as springs. Since the movement is
>not that great it should work fine. Can you give us more details?


        What I did on my first cell is easiest to explain:


        The cell was constructed of a circle of plywood, and a second
piece that was cut into a Y shape. The y shaped part was what actually held
the mirror.

        On the "Y" shape, I drilled a hole in each leg, near the end
of the Y. In this hole, I placed a captive nut. After RTV'ing the mirror to
the cell, the cell was supported onto the circular piece by three knobbed
screws, which stuck out the back of the cell.


        Now we come to the Superball part. I used balls that were
about an inch and a quarter. I cut them in half, and glued them to the
circular part of the cell, immediately between the adjustment bolt and the
center of the cell.


Some bad ascii art showing one of the adjustment bolt areas side view:


        _________________   Y shaped portion of cell

Bolt       ||  /---\   Superball half
        ___________________ Bottom of Cell
           ||
        |------| knob

        The superball material has worked well It has a very good
tradeoff between stiffness and springiness. It holds the bolts right where
I leave them after collimation.

        Remember to put the adjustment bolts in an area where they
won't contact the mirror.

        As for the choice of material, I would suggest metal over
wood. My original cell was meant to be more of an experiment, eventually
making a metal cell, but the darn thing has worked so well, even with three
point support (it's a full size blank) that I just kept it as-is. It has
held up since 1999, so I'm pleased.

        - Mike -

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