RE: [ATM] Testing the limits of ATM technology

["lou krajci" <loukrajci@comcast.net>]

>From: "Daniel Bakken" <dan@runway.net>

>...For
>example the truss tubes currently at 1.125" diameter are probably
>undersized, although it does function, just not stiff enough....

For such a size scope...and the 'long' f/ratio you have...something more
like a Warren truss (or something like the Warren truss) may be called for.
See:
http://overton.tamu.edu/aset/krajci/
specifically:
http://overton.tamu.edu/aset/krajci/scope-design.htm
and mostly
http://overton.tamu.edu/aset/krajci/truss.htm
and especially
http://overton.tamu.edu/aset/krajci/truss-analysis/truss-analysis.htm
for some structural analysis of some truss ideas....what I call the X-brace
or double X-brace is similar to a Warren truss.  Use of such a design may
allow you to use shorter free lengths of truss tubes (to eliminate 'floppy'
tube syndrome)...and (in a Warren truss design) if you scale the truss
member cross section to match the expected load...you'll use thinner truss
tubes in the upper part of the Warren truss (saves on weight and wind load
and balance issues) and thicker tubes on the bottom of the Warren truss
(which is where they are needed).

Note the warning I put at the bottom of:
http://overton.tamu.edu/aset/krajci/truss-analysis/truss-analysis.htm
that stars with:
"Also, if you want to design your own 8 member truss, here is a warning..."

Also see:
http://overton.tamu.edu/aset/krajci/dobsonian/dobsonian.htm
for ideas on:
- an upper ring (lower wind profile than a cage)
- having the focuser in a 'not low profile position' (to improve baffling,
which also keeps wind profile down)
- damping material on spider vanes (wind proofing)
- damping material on (inside and surrounding) truss tubes (wind proofing)

I hope this helps.

Tom Krajci
Albuquerque, New Mexico
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