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


John Vede Dudgeon wrote:

>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
>
>
>
Thanks John!!!  The 54 point looks like a true winner, but the complexity
of making such a beast may keep me limited to the 27 point design, which
others have indicated it totally adequate.

Lawrence Sayre

--
My philosophy, in essence, is the concept of man as a moral being, with his
own happiness as the moral purpose of his life, with productive achievement
as his noblest activity, and reason as his only absolute.

Ayn Rand (in the appendix to 'Atlas Shrugged')

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