Re: ATM Briefcase string scope

[John Swenson <johnswenson1@home.com>]

I finally got the carbon fiber tubes installed in the "simulator". The
results are quite a bit better than the threaded rods, they are quite a
bit stiffer and don't buckle until MUCH higher forces (and they are a
lot lighter). 

The resulting truss is quite stiff to sideways forces, but giving it a
good whack (the old whack test) causes some oscillations that last quite
some time. If its oscillating SOMETHING has to be giving, it doesn't
seem to be the string, that 450 plus is incredible. After some careful
observations it looks like it is a combination of the bottom plywood
plate bending and the turnbuckles and screw eyes bending. The screw eyes
I can replace with holes drilled directly in the wood blocks, but the
turnbuckles are going to take some thought though. (Or maybe I should
leave it alone, the forces necessary to get it to flex are MANY times
greater than what would cause the scope to move on its axis)

After working with these carbon fiber tubes, I'm getting pretty excited
about their uses. It occurred to me that the I could make the entire
secondary cage (ring) as a carbon fiber truss arrangement. My
preliminary tests show it would stronger and more stable than the
plywood ring and quite a bit lighter (and much cooler looking!) but a
bit more expensive and take more time to construct. 

Does anybody know the best way to join the ends of the tubes together in
such a truss arrangement? Right now I'm overlapping the ends and
wrapping them with carbon fiber tape and putting several drops of CA
glue on the tape (sort of like the lashings I used to do in Boy Scouts).
It seems to work but looks sort of "unprofessional". Just butting the
end of one tube up to another seems like a much weaker joint. The tubes
are only a couple of inches long so fairly thin ones are quite strong. 

This project has turned into a lot more experimenting than I had
originally intended, but I'm having fun!

John S.