Re: [ATM] Plop Flop II The Sequel

["James Lerch" <jlerch1@tampabay.rr.com>]

Jay,

Here's my take on how to build a 27 point cell based on Plop results.  BTW, for
reference we used plot to create this cell for a 22" F/6 made from 3/4 edge
thick plate glass (I highly recommend against this type of project, but it does
'OK' on low powers)

http://lerch.no-ip.com/atm/Projects/Ron_Cell_Small.jpg

So here's how I do it...

#1 Run Plop's automated cell design

#2 Once complete, click 'Graphic Plots / Cell Parts' and figure out how to print
it for future reference on how the finished cell should look

#3 click 'Graphic Plot / Part Dimensions'
    A) Get some graph paper
    B) For each part, draw the triangle full size to create a fabrication
template
    C) Mark the support points and CG (in red)
    D) For a 27 point cell, you'll need three of each part
    E) Fabricate the parts, making them slightly larger than the template so you
can assemble it

#4 Once you have all the part cut, got to the "Edit as Text" Tab, find "Var
radius0-2".  Multiply these values by your mirror diameter.  Draw these three
radiuses on the back of your mirror, this is where the support point for each
cell part must coincide.

#5 Stack / assemble the cell parts up, and the only remaining variable is the
angular spacing between the three separate stacks of support triangles.  Simply
adjust the stacks until the spacing between the inner three triangles is equal.

BTW, in the image I referenced, you will see small ball bearings embedded in the
silicone.  This is a BAD idea!  The problem is the silicone shrinks a little as
it cures.  If the pad of silicone is not centered on the bearing, once cured it
shrinks, causing uneven pressure on the support points.  This uneven pressure
was easily seen in this super thin 22" optic.  We re-glued the cell using
spacers that were removed after the silicone cured, which worked much better.

Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)

"Anything that can happen, will happen" -Stephen Pollock from:
"Particle Physics for Non-Physicists: A Tour of the Microcosmos"

" Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent. "
                                                           Calvin Coolidge


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