[TowerTalk] Fwd: Grounding connection to tower legs

[Grant Saviers]

Another subtlety is the recent standards requirement for two hole 
compression lugs plus antioxidant between surfaces for all bonding wire 
terminations.  I think the idea with two hole lugs is to prevent 
loosening of a single bolt attachment from movement of the wire, not so 
hard with 2 gauge wire.

Grant KZ1W

On 10/16/2017 5:26 AM, Ward Silver wrote:
>> 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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