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Re: [TowerTalk] Tack welding rebar

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Tack welding rebar
From: N3AE <n3ae@comcast.net>
Date: Sat, 4 Jan 2014 17:50:47 +0000 (UTC)
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
A local metal fab shop a few miles away told me they prefer tack welding rebar 
cages because wire-tied cages don't hold shape well in transit. Not sure I buy 
into that, particularly if diagonal bracing is used, but that's what they told 
me. 

The discussion did raise some questions for this novice tower installer. Hoping 
to put in a base this spring for a UST TX-472 (4x4x7 cage ...probably weighs 
about 250 - 300 lbs). 

1. If the cage is constructed near (not in) the hole, what's the best way to 
rig it for lowering it in with a backhoe? Seems to me that just tying some lift 
straps to the top horizontals at the four corners might pull the cage out of 
shape or pull the horizontals off, particularly if wire-tied vs welded. 

2. There's another rebar cage fabricator further north that has automated 
machinery for cutting and bending. Would it be feasible to have them just cut 
and bend the pieces, toss them in my pickup truck and construct the cage 
on-site? Reason I ask is I'm not sure if building a cage requires measuring and 
cutting as you go to deal with tolerances. I would guess the fabricator's 
automated machinery would hold better tolerances on bend radius and bend 
location than manual tools in the hands of a novice builder. 

3. What's the proper way to electrically bond the tower anchor bolts to the 
cage to get a good Ufer ground? The anchor bolts are galvanized. 

4. Not really a question, but it's annoying that UST requires a 7 ft deep cage. 
From what I understand, rebar stock typically comes in 20 ft lengths. If the 
depth was 6 ft 8 inch, you could get 3 vertical pieces out of that 20 ft stock. 
Perhaps a practical reason for asking about required rebar lap splice overlap 
if you have to extend a length. 

Thanks & 73 

Shawn - N3AE 






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