On 3/24/18 11:39 AM, Hans Hammarquist via TowerTalk wrote:
Jim,
So what you are telling me is that it would be OK to use the $3 anchor bolts
for freestanding tower?
No, it's just that you can design something to use whatever components
you want to use. Not every design needs A286 bolts that have been
individually x-rayed for defects.
Regular old Grade 2 5/8" bolts from the bin at Home Depot might well be
more than good enough, depending on the loads and the redundancy in the
design.
I guess I was overly pessimistic when I anchored my tower with 12 bolts into
granite and added guy wires to it. My calculations show that it should
withstand 130 mhp wind with 20 foot^2 on top. Could I take the guy wires off
maybe? It would make it a lot easier to haul up antennas that way.
130 mi/hr is about 40 lb/square foot, so that's a 800 pound lateral load
at the top of your tower, plus whatever the load on the tower itself is.
What did the engineering calculations show? Most guyed towers (as in
"designed to be guyed") have very weak base attachment (if any, beyond
what's necessary to keep it from skidding), and can't take a lot of
bending. they take compression loads, and the guys take the lateral loads.
On the other hand, you're probably not going to be hauling antennas up
in 100 mi/hr winds...
<grin>
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