From: John Vede Dudgeon 
To: atm{at}shore.net
Reply-To: John Vede Dudgeon 


Larry,

I have recently become somewhat familiar with generating PLOP cells, and
tried to build one to your RMS parameters. I cannot get RMS error to
1.5e-06, the closest I get is 4.08716e-06, or 1/122.33 waves RMS, which
isn't too bad.

One problem I have with the 36 point cell in PLOP is placing the support
bars on the outside triangle points in two different rings, with three
rings total support. If you could manage this, I think you could get better
RMS values, but not down to 1/333.33 wave. The difference is not trivial,
but may be many orders of magnitude less than other error inputs. Below is
the 54 point cell text file (and 36 point) I originally designed for my
30" plate glass 1" thick f6 Cassegrain mirror cell, tweaked for
your parameters. I have pilfered a couple of good ideas for cell pivots
from the list, and hope to reduce the degrees of freedom/slop in axial
motion to the minimum.

Your parameters produce RMS error of 8.97294e-07, or 1/557.23 waves RMS
error. I have very little experience here, but it seems that other design
features and material constraints will be the limiting factor in use.


John


Plop text (copy and enter into text box on "Edit as Text" tab)

;JV Dudgeon
;This is a conventional 54 point cell with support radii and angles
;optimized by PLOP. Pyrex glass mirror diameter (762 mm), thickness
;(40 mm), focal length (3048 mm), and secondary size (127 mm) are
;fixed design elements.
diameter 762
thickness 40
density 2.23e-06
modulus 6400
poisson 0.2
focal-length 3048
n-mesh-rings 30
rel-support-radii 0.236309 0.501197 0.702185 0.880619 num-support 6 12 12 24
support-angle -0.000344064 29.9997 14.9996 29.9997 basis-ring-size 6
basis-ring-min 0
obstruction-diam 127
optimize rel-support-radii 0 0.1
optimize rel-support-radii 1 0.1
optimize rel-support-radii 2 0.1
optimize rel-support-radii 3 0.1
optimize support-angle 0 0.1
optimize support-angle 1 0.1
optimize support-angle 2 0.1
optimize support-angle 3 0.1
part triangle 6 point 0 0 point 1 0 point 1 11 part triangle 12 point 2 0
point 3 0 point 3 23 part triangle 6 part 0 0 part 1 0 part 1 11 part bar 3
part 2 0 part 2 1



;JV Dudgeon
;This is a conventional 36 point cell with support radii and angles
;optimized by PLOP. Pyrex glass mirror diameter (762 mm), thickness
;(40 mm), focal length (3048 mm), and secondary size (127 mm) are
;fixed design elements.
diameter 762
thickness 40
density 2.23e-06
modulus 6400
poisson 0.2
focal-length 3048
n-mesh-rings 24
rel-support-radii 0.401155 0.825991 num-support 12 24
support-angle 0.00196028 10.002
basis-ring-size 12
basis-ring-min 0
obstruction-diam 127
optimize rel-support-radii 0 0.1
optimize rel-support-radii 1 0.1
optimize support-angle 0 0.1
optimize support-angle 1 0.1
part bar 6 point 0 0 point 0 11
part bar 12 point 1 0 point 1 23
part triangle 6 part 0 0 part 1 0 part 1 11 part bar 3 part 2 0 part 2 1


///\\\///\\\///\\\///\\\///\\\
John Dudgeon
University of Hawaii at Manoa
Department of Anthropology
Department of Cellular and Molecular Biology 2424 Maile Way
Saunders Hall, 346
Honolulu, HI  96822

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