upper cage weight ?

[GrahamL]

I'm building a 12" (f5) truss dob atm .. lots of fun so far
I'm looking at the upper cage atm with regard to how much weight
is acceptable .. the ground board/box , alt bearings and mirror box are all a double laminate of 12mm ac ply.. yes its a little bulky but it is strong and still fairly light .. I could use the same for the top but am unsure if the little extra weight will be an issue .. at a guess the upper cage with focuser board will be a little over /under 4 pounds , with the secondary
and focuser still to be added to that .. to much ??

many thanks

[Blue Skies (Jacquie)]

When I redid our club 17.5", I realised that the secondary cage was going to end up a little heavy, mainly due to the finderscope. Rather than building the mirror box higher to counterbalance it, I planned to use a virtual counterweight, or spring counterweight. It works well, but I also had to add some lead to the bottom half to make it a bit more even. iirc the ratio is 3 times as much weight has to be added to the bottom half to counterbalance the extra weight at the top.