[TowerTalk] Recommendation for mast on bottom mount

Jim Jarvis jimjarvis at verizon.net
Mon Sep 18 01:59:09 EDT 2006


W3GM used bottom mount rotors on all of his 100' 25g towers.

The actual mast and the 'torque tube' were of different material.

He used thin-wall irrigation tubing, 100' of which weighed maybe
20 lbs.  No idea what % of that was carried by the rotor, and what %
might have been hanging from the thrust bearing.  The load was
light, in any case.

The effect of this was to allow the arrays.. 3 el fullsized 40, for
example...
to rotate in the wind somewhat, taking peak loads off the rotor. I think he
turned the 40m array either with a tailtwister or a ham-4.  In the time
I operated from there, maybe 4 seasons, I never remember a major rotor
problem.

n2ea





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