[TowerTalk] Rebar Cage

[Bob Otto]

Hello Ted,

I thought the previous advice from Steve, K7LXC, to contact the
manufacturer regarding the rebar requirements was pretty good advice.
I know many people just throw rebars in the hole and figure "that's
good enough". Rebar cages for free standing towers are much more
critical than for guyed towers as the stresses presented to the
concrete are much different.

When I recently put in the base for my Heights Tower Systems aluminum
free standing tower, I used the plan provided from Heights.  It called
for a rebar structure that was 3" from the outside of the concrete in
all planes (sides, top, bottom).  It also called for layers of #4
rebar spaced 12" apart except the top four layers which were 4" apart.
There also were vertical rebar members spaced no more than 18" apart.

After constructing the cage and placing it in the hole I make about
four connections using clamps to various places on the rebar cage.
Next I placed #4 solid copper from each clamp to a 6' copper clad
ground rod placed in the very bottom of the hole.  I made sure that
all the "wire ties" used to tie the horizontal rebar to the vertical
rebars were tight so there would be a good connection.  I also put a
clamp on the rebar welded to each tower leg and ran #4 solid copper to
the same ground rod in the bottom of the hole.  If I had it to do
again, I'd have put several ground rods in the bottom of the
hole....but I guess one is MUCH better than none!  <G>  These ground
connections were not to replace a good tower leg ground, they were in
addition to the planned tower leg grounds.

Hope this information helps.

73 from.......

Bob Otto
N8NGA@one.net
Cincinnati, Ohio

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Wednesday, November 01, 2000, 11:31:18 PM, you wrote:

TJW> Am fixing to put the 55 foot free standing crankup back up...Whats the
TJW> rule of thumb for building the rebar cage to go in the hole....At the
TJW> previous QTH I bent it around the uprights but have heard a couple guys
TJW> say that was a lot of extra work and not necessary just to take straight
TJW> horizontal pieces and tie them together at the corners...Whats the
TJW> consensus????Also how many Vertical and horizontal pieces would be best,
TJW> hole is about 4.5 feet squre by 5.5 deep...Also see something in U>S>
TJW> Tower catolog 3/8 O Tie Bars @ 24" O.C.....Have no idea as to what they
TJW> are refering to and didn't use it previously just some VERY large
TJW> washers at the bottom of the anchor bolts....Thanks,
TJW> Ted K9HUH    "HUH"

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