Agreeing with Roger, having just completed building for a friend a new
cage for a Tri-Ex LM354, I welded the main #8 rods to the tower mounting
flanges (3x3/8x20" HRS). This is the way it comes from the factory and
there is no alternative, so debating weld/not weld is not relevant.
The factory cage also ships from the factory with #3 & #4 rods tacked to
the #8 to provide a strong enough cage to be shipped. This also insures
the base flanges mate with the tower flanges with no additional and
difficult fixturing and supports when pouring the base concrete.
Of course, weldable rebar should be specified, but the entire cost of
all the base rebar was under $100 cut to length by the supplier. We bent
the #3 loops around the #4 extensions to the #8, and then I tacked these
all together. Wire ties are very handy to fixture the assembly for welding.
This all was a superior way to build a cage when compared to the
troubles the wire tied cages gave when installing my two HDX589s. Expect
some climbing on the cage when it goes down 9' into a hole only slightly
larger. (or 6' for the LM354).
My .02,
Grant KZ1W
On 4/13/2014 12:45 AM, Roger (K8RI) on TT wrote:
On 4/13/2014 1:47 AM, Brian Amos wrote:
If you weld it the rod may rust which will cause the concrete to burst.
Rusting requires an oxidation source. Rod protruding from the
concrete, or flux. I'm using Metal, Inert Gas or MIG for short. I'd
not want to use stick welding. These are "tack welds, not true welds.
They are just enough with what wiring I can do with one hand, that I'm
not worried about the cage changing shape before we pour the
concrete. The "twist" is much like we use on aircraft nuts and bolts,
except we are using soft iron and not #20 or 24 SS.
I'm used to sticking the two ends into a tool, pulling a handle that
reminds me of a Ty-Wrap tool. Just about instant twist.
The Iron wire is large enough , #14 I think, that it can be twisted
with regular pliers.
Tack welds are small enough that I'm not worried about changes in
strength.
There are 3 major welds. Those are ones holding the 1/2" X 3" X 25"
ears to the #10 rerod The tower and raising fixture bolted directly
to these.
If we could get the rerod to stay in place we wouldn't need to fasten
it. The rod just serves as a reinforcement for the concrete, although
with the LM470 the big stuff that holds the tower is part of the cage.
I like the idea of everything connected as it serves as a very good
UFER ground. Course that connects to a network of over 600 feet of
bare #2 that is cad welded to 32 or 33 8' ground rods.
Speaking of grounds. I've lost 2 of the big Diamond dual band
(144/440) antennas. I think I've lost a system ground in the shop and
it went to ground through the antenna.
73
Roger (K8RI)
Not
a fun situation as usually the recommended repair is completely
remove the
foundation and replace it. As a foundation engineer I only hear the
failures and what the standard of practice and code say, so maybe it has
worked under the right circumstances. If it has an issue and it was not
built to code the insurance company will not cover you.
Tying rebar is not fun and can be hard work but stout teenage boys will
learn quickly and work for a small portion of what a concrete company
would
charge. I usually offer a favorite meal ajdand tgat is ebough. You may
even find some free and experienced help from your ham club. I know
whenever someone in my club needs help with something that falls
within my
line of work I am more than willing to lend a hand.
Brian
KF7OVD
On Apr 12, 2014 10:42 PM, "Edwin Karl" <edk0kl@centurytel.net> wrote:
Roger,
As part of my mis-spent youth I was an iron worker, worked at it for
about
6 years.
We were referred to as "rod busters" by some. In any event installed
lots
of iron
in the new York area.
Now that I'm retired, I built my own home, not with my hands, but
was the
general
contractor. You can do that in the country ... I did do the reinforcing
myself; so my
driveway, sidewalks, patio, basement walls and floor all have steel
internally. The
also barn has a reinforced concrete floor.
The tower is an AN Wireless 90 footer with a big foundation, rear 3
layers, top bottom
and middle is about 12 feet deep, took 21 yards of concrete to fill the
hole. There is a
section of tower made to go in the foundation which splices to the
rear.
Now I'm saying all this because of a decision I made years ago, if I
had
the chance, this is
how I would choose to build my own home, etc. It might be nit
picking but
the issue with me
probably pertains more to structural iron, like the tower etc. Don't do
anything like welding
which may change the characteristics of the iron negatively. Also
affects
galvanizing etc.
Probably way over thinking the issue, which I usually do.
I also will confess in my day, except where cad welding 1 1/4 rear for
power houses etc,
never saw rear welded. Generally a splice is 20 times the diameter
side by
side and double
tied.Compared to structural, rear is soft, we would bend it on site for
hooks and angles, so I
suspect it's already not too stuff. But as I said initially the bar
reinforces the concrete, which
holds the bar in place.
Sorry for being so lengthy ... but, if there are other issues as you
mention than explain why welding
might be acceptable. We would take columns and beams using wire to
kind of
guy it internally, if
the item has a long way to go or was a difficult pick for the crane
etc.
If you are having the job
fabricated off site it probably could be done either way, if you're
alone
tack welding could work.
I wish you well, and would appreciate hearing from you as the project
progresses.
By the way, 8 or 9 inch lineman's pliers and end cutting nippers are
tools
of the trade, The nippers
work real well when tightening the connection, After a few mistakes,
you
can get the hang of it.
Very 73!
ed K0KL
On 4/12/2014 9:37 PM, Roger (K8RI) on TT wrote:
On 1/5/2014 12:58 AM, Roger (K8RI) on TT wrote:
On 1/4/2014 4:01 PM, Ed K0KL wrote:
I can't stand it any longer ...
And the problem is?
If wired in place or near the hole they work fine. If shipped, or
handled
a lot they seem to come already welded.
As I only have one useful hand, tack welding is faster, easier, and
makes
for a far more secure joint than wiring one with just one hand.
I noted when at my steel supplier, they had a cage, mostly done
that was
all welded. The customer would put it on a trailer, haul it 10
miles or so
and then stick it in the hole with the same dimensions as when he
picked it
up.
73
Roger (K8RI)
Wire ties are fine to keep the rebar touching from bar to band (the
smaller rod surrounding the
verticals or horizontals as it were). It has been used for years on
buildings, roadways, etc. Generally
speaking the concrete holds the connection together, the
connection and
rod make the concrete
strong ...
Order towers with the rebar cage and they likely will come welded and
not tied.
That's been the local experience.
73
Roger (K8RI)
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