[ATM] Collimation bolts and torque

["Alan K. Henderson" <alankh@ev1.net>]

Refer to this diagram:

http://users3.ev1.net/~alankh/Cells.gif

(Drawn to scale. The mirror has a quarter-inch bevel all the way around -
note the odd shape.)

These are cross-sections of mirror cell designs I've been doodling. The cell
itself looks something like a tailgate; it is designed to allow for the wide
placement of the collimation bolts, allowing for better fine-tuning. The
image on the right applies that design to a typical mirror (I was too lazy
to erase the bevel), and the second design applies it to my mirror. Not only
is my mirror twice as heavy, but the center of gravity is farther away from
the collimation bolts - putting both more weight and more torque on the
bolts.

Question: is the increase in torque significant enough to consider a cell
design that places the collimation bolts closer to the mirror's center of
gravity? The third design adds about a pound to cell weight (an extra 14" of
steel tubing) but results in roughly even amounts of torque on either side
of the point where the collimation bolts join tailgate to cell. This is
probably overkill - if the torque increase is significant enough for worry,
something in between the second and third designs would suffice. Any
thoughts?

Note also that the third design reduces the height of the entire assembly by
an inch, since the tailgate overlaps the cell.

Alan K. Henderson


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