[TowerTalk] Tack welding rebar (N3AE)

[Dr M J DiGirolamo]

Shawn,

  I went through all this a few years ago.  I have posted many photos of the
entire sequence (including the answer to your question #1).  You can start
here, then snoop through them all..

 
http://s287.photobucket.com/user/Apostle10/media/Rebar4.jpg.html?sort=3&o=78

  If you have any questions or comments, feel free to contact me, Mike at
w4xn dot com

73,

Mike, W4XN
http://www.w4xn.com


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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