From: Dale Eason 
To: atm{at}shore.net
Reply-To: Dale Eason 


I have been giving thought to how I will build the truss for my 16"
f5.  I already have an 8" f8 truss scope and think I understand it
pretty well.  I designed it using Grape finite analysis about 5 years ago. 
It has lived up to the Grape simulation.  I am trying to make the 16 incher
an ultra light.  Keeping the truss tube weight down is important.

It seems to me that in the standard 8 tube truss for a Dobsonian
alti-azimuth mount that only the left and right sides need to be very
strong as they carry the weight of the OTA load against gravity.  The left
and right pair only help to keep the OTA from rotating and aligned left and
right  to the mirror when the OTA is pushed by a sideways force.  Usually
that side force is much smaller than the altitude force.  Thus I think that
the upper and lower trusses can be made out of much smaller diameter tubing
saving a lot of weight.

I know that some have gone to a 6 tube truss but I'm not really ready to do
that yet because I can't figure out how to attach it to the square mirror
box.  I guess I should look closer at Mel's pictures.

Anybody have any thought about reducing the left and right truss diameters?

Dale Eason

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