From: "Tom Krajci" 
To: 
Reply-To: "Tom Krajci" 


From: Ross Sackett 

>Oh, ugh.  Both cells look a little nightmarish to me,
>especially the one with the long springy outer
>triangles.

That's why I asked for feedback and comments.  ;-)  Yes, the skinny
triangle idea is not good for more than one reason (Nils mentioned another
reason).  I've since updated more info and diagrams to my page at:
http://overton.tamu.edu/aset/krajci/cell-12-pt/cell-12-pt.htm

>Wouldn't a PLOPed Hindle-style
>("Hitler-era") 16 point cell be simpler to build and
>support the mirror better?

Hopefully my examples (with help from Nils) show more practical
applications of a 12 point support that are not difficult to build - only
beams in some examples.  Easier to build than a Hindle 18 point support? 
Actually it looks, in terms of moving parts and arrangement/layering of
them...to be identical...just that it uses 12, not 18 points.

Will it support better?  I'll let PLOP answer that.

>Since when did support points become an endangered
>species in need of such radical conservation?  I
>remember a thread a couple of weeks ago about the
>macho  appeal of building the ultralightest ultralight
>on the observing field, inviting a lot of hemming and
>hawing about other reasons to build the beautiful
>creatures, too (low wind resistance, lone-nerd
>portability, etc.).

My main goal here is to go through a design exercise and learn how to
design better mirror cells.  (Actually, for my 16 inch CCD scope...I only
need a six point support for a 1.5 inch thick mirror....but some day I'll
scale up to a larger mirror, and then I'll need more support points, with
more layers of pivots.)  If you want to...you can think of my webpage as a
design sketchbook that I'm making public...warts and all.  As my knowledge
gets better, I'll make improvements to the webpage.

As I stumble through this process I'll try and strike a balance between
complexity of the cell, and number of support points.  I will not put the
design criteria of 'absolute minimum of support points' above mechanical
simplicity of the cell design.  (Although I'm not afraid to design an
asymmetric cell that may look strange at first glance.)

>Ok, I guess I finally need to build that one-masted,
>carbon-epoxy 18" with the 5-point cell and
>teflon-sheet groundboard I've been designing :)

Got any diagrams you care to share with us?  ;-)

Tom Krajci
Tashkent, Uzbekistan


-+-
Outgoing mail is certified Virus Free. Checked by AVG anti-virus system
(http://www.grisoft.com). Version: 6.0.419 / Virus Database: 235 - Release
Date: 11/13/2002

--- BBBS/NT v4.00 MP