In a message dated 12/18/2007 6:51:54 P.M. Pacific Standard Time,
towertalk-request@contesting.com writes:
> I am constructing a tower base and have tried to read about the subject as
much as possible. I have a few questions which I hope can be answered via
this forum.
> Tower is Triangular 3 x 7 M sections Crank Up tower tilting over at 2
meters. Soil is a solid Red Clay soil. What I could gather is that the base
should at least be 1Meter deep (Form soil level) so the hole I dug is 1M x
1,7M x 1,17M and then about 150mm of concrete will be above soil level - the
bolts used to tie down the base will be approx 100mm above the concrete.
Gather from where? The LXC Prime Directive is always to "DO what the
manufacturer says." What do they say? In the absence of manufacturers info,
have an
engineer verify the load and calculations. You may have someone who can do it
in your local radio club.
> My question is about the cage. I am using 16mm Re-Bar. I have read that
the
rebar cage should be around 300mm away from the side of the Concrete block
to ensure its away from the soil at the bottom and sides.
> Is this correct?
Yes. You don't want the rebar touching the dirt. Over time, the moisture in
the soil will attack the rebar and it'll exfoliate rendering it useless.
> Secondly I have read that the cage is made with binding wire or cable ties
and not welded.
> Is this correct?
Yes. Most rebar is made from scrap metal and the exact composition is
questionable so trying to weld to it is difficult. Tying it is the correct
method.
Sometimes rebar can be brazed but you need to know what you're dealing
with in order for it to be successful.
> Now my towers' base gets tied down with 3 threaded bolts of 1 meter each
> Do I weld these three bolts to the cage? If not how is it connected? I
know
that somehow the 3 bolts must be electrically connected to the Rebar cage
for earthing purposes.
It's easier to weld the anchor bolts together into one fixture and then tie
it to the rebar cage. That way you can level it regardless of whether the
cage is plumb or not. To make the bolt fixture, attach the bolts to the tower
base and then have a welder tack weld them together on the top and the bottom;
rebar is fine for the bracing. This way the tower is guaranteed to fit the
bolts and they won't come out of alignment during installation.
> Lastly I see many drawings that the ends of the vertical bars of the cage
are bent - why is this and is it really necessary?
Don't know. If that's what the manufacturer says, then I would follow it.
Getting that engineer involved might get you an alternative design.
Cheers,
Steve K7LXC
TOWER TECH -
Professional tower services for hams
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