Mirror cell: Adding more points?

I have a standard 9-point-support 16" cell and a 16.5" f/4.5 1"-thin quartz mirror.

Although there were a few old posts on the ATM List that this is actually fine, I'd appreciate suggestions on improving the cell. Is there a way (physical and geometric designs) to add another layer of points without completely rebuilding the cell?

Appreciated, -- William

If you float a triangle with three points at each of the 9 existing points you will have a 27 point floation cell. Check the Kreige & Berry book for instructions.

Walt

Thank you everyone for replying!

The geometry looks fairly standard, though the outer pads are not quite equally spaced. However it is possible to fit a 7"-per-side regular hexagon over the triangles using smaller or tapered pads placed nearer the corners.

I took some (not extremely precise) measurements: (R = radius from center of cell)

cell rim 8"R (16" ID; I'll probably cut away most of it)
triangle outer vertices 7"R
triangle outer pad center 6 1/4"R
triangle pivot bolt center 4 13/16"R (this is probably important)
triangle inner pad center 3"R
triangle inner vertices 2 1/2"R
pad diameter 3/4"

My options are:
(1) use it as is (after de-rimming)
(2) shift outer pads to form a 7" regular hexagon, inner pads to compensate
(3) add a 27-point layer using existing triangles (won't be optimal a la plop)
(4) replace triangles with bars to make a 6-point cell
(5) replace triangles and make an 18-point cell (I have some old parts)
(6) start from scratch, or commission a new cell!

My mirror box measures 20" square INSIDE.

-- William :S

Michael,

Thanks, yes the existing cell uses bolts and the holes are too big. Not having a machine shop (nor a lot of time) my options are limited. I do have a Dremel and basic hand tools.

I had thought it was 16" when I bought the mirror here, but it turned out to be closer to 16.5". Nobody sells a 16.5" cell. (And the mass produced ones might not be any better.)

Would you happen to have parts you can spare (or part-numbers), that aren't too difficult to make use of?

-- William