[TowerTalk] : Nube rebar question

[James Wolf]

Kelly,

I can't say how a pier pin is supposed to work, whether it should allow
twisting or not.  In my case, the rotor is down at 66 ft. and I have torque
guys at the rotor and also at the 100 ft. level to prevent twist.  The top
20 ft. of the tower rotates.
But certainly, if the base was imbedded in concrete, it wouldn't be allowed
to twist.

Jim - KR9U


-----Original Message-----
From: Kelly Taylor [mailto:ve4xt at mymts.net] 
Sent: Wednesday, December 17, 2014 11:49 AM
To: K7LXC at aol.com; towertalk at contesting.com; jbwolf at comcast.net
Subject: Re: [TowerTalk] : Nube rebar question

The roof mounting plate, as described, seems to solve a few issues relative
to embedding tower sections or base tubes in concrete < helps prevent water
intrusion into the base, permits re-use of base for other towers, etc. < but
leaves one issue unresolved. At least, it does if I'm reading the
description correctly.

The OP mentioned he uses threaded rod to keep the base from twisting, but
wouldn't you WANT some twisting at the base? Isn't that the rationale behind
using a pier pin instead of any kind of fixed base? In other words,
torsional forces reaching the base of the tower result in nothing more than
slight rotation around the pin rather than becoming a source of fatigue
failure in the legs?

Did I miss something in 20 years of towertalking?

73, kelly
ve4xt