Good Morning All, and I am reading along this with interest given past
posts
as to the what/where of properly using worm-gear type clamp products.
Ward ... please note that some suppliers DO seem to suggest their use?
http://www.polyphaser.com/products/grounding-and-bonding
On the other hand, and from the daily calls/email here as to "can I do
this or
should we do that?" with various clamp products, there are many many
design
factors that really need to be properly considered with this topic.
So given the various present unknowns here (clamp type, bandwidth,
thickness,
type of materials and so on) I can't fully agree or disagree with your
statements
as to the use of worm-gear clamps for such applications. But it is
interesting ...
Basically this topic comes down to risk management. And as one who in
times
past did things poorly and suffered the consequences in the form of
canceled
insurance, and extra work/time/investments to overcome the root causes
....
I would suggest each person understand their specific risks, study
appropriate
sound technical information (such as Ward's book!) to decide what to
do there.
73 de Billy, AA4NU
Disclaimer if needed: Product Manager - Ideal Clamp Products.
------------------------------------------------------------------------
*From: *"Ward Silver" <hwardsil@gmail.com>
*To: *"Reflector" <towertalk@contesting.com>
*Sent: *Monday, October 16, 2017 7:26:02 AM
*Subject: *Re: [TowerTalk] Fwd: Grounding connection to tower legs
> Why would the hose clamp blow apart? I have used this method for decades
and have had multiple direct lightning strikes.
The mechanical forces on a conductor carrying kilo-amp currents from a
lightning strike can be extreme - many pounds per foot of conductor. (This
is described by Ampere's Force Law.) That's why codes require ground
conductors for lightning rods and antennas to be secured to a building or
support structure. (This was news to me, too.)
Basically, the conductor experiences a huge jerk which would destroy
either
the conductor or whatever is trying to secure it - like a hose clamp. So
it would be more accurate to say that the hose clamp is not rated to
withstand the force experienced by the ground conductor and is not blown
apart by the current. It's the mechanical force.
If hose clamps have been used and the tower has taken hits without
damaging
them, then the ground conductors are not for whatever reason carrying
enough of the current pulse to generate damaging forces. Or maybe the
configuration of the conductor was such that the force was weaker than it
could be. i.e. - you got lucky :-)
I'm no different in that I've used hose clamps over the years for similar
applications and got away with it. No more. As long as we're in True
Confessions mode, I've used braid from old coax (outdoors, even!) and
soft-soldered strap and braid to ground rods. No more of that, either.
Live and learn, especially now that I live back in the lightning zone
(Missouri) with towers on a high spot.
So the advice is just to use the right stuff for the job. It's not that
expensive (a lot less than your insurance deductible, that's for sure) and
has been engineered to minimize corrosion and handle the mechanical
requirements of the application.
I also got a question about CadWeld and those are great for ground
electrodes but I would never use them on the tower itself. It may be
possible to safely weld a connection to a tower but I wouldn't do it to a
tubular load-bearing leg, not to mention the dissimilar metals
involved and
all that. I wouldn't want to weaken a cross-brace either, especially when
there are other options designed for that exact application. Maybe someone
with broadcast tower experience could weigh in on that. I repeat, for us
hams, just buy the right stuff and and do what the manufacturer says.
73, Ward N0AX
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