[TowerTalk] Fwd: Grounding connection to tower legs

[Billy Cox]

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. 

----- Original Message -----

From: "Ward Silver" <hwardsil at gmail.com> 
To: "Reflector" <towertalk at 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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