I am not aware of any other type of clamp other than the stainless hose
clamp type with the shim that is suitable for connecting ground strap to a
tower leg.
Unless there is a bolt available where the strap can be sandwiched between
compatible materials.
> 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 :-)
This is one reason it is recommended that ground leads be run to ALL tower
legs. It divides the current up so that no one lead is carrying all of the
current.
Also the cables coming off the tower share the current as well as the tower
itself.
I have not heard of any of those types of clamps failing due to lightning.
They provide a large surface area of contact with the tower leg for copper
strap.
>but my understanding from Polyphaser folks was these
> are not to be used as primary grounding clamps for heavy conductors.
> These are just to attach some kind of light-duty strap or wire (or
> braid!) to a galvanized pipe, tube, or rod. For the main ground
> connection that is intended to handle the lightning surge, you have to
> use the heavy-duty clamps.
I think the takeaway from this is that a heavy cable should not be put under
the stainless hose clamp device. The reason being that you will not get the
full surface contact with the heavy wire under this type of clamp. They are
designed for strap connections. Other types of clamps should be used for
wire connections.
Never use braid.
73
Gary K4FMX
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
> Ward Silver
> Sent: Monday, October 16, 2017 11:57 AM
> To: Billy Cox
> Cc: Reflector
> Subject: Re: [TowerTalk] Fwd: Grounding connection to tower legs
>
> A quick reply - yes, the stainless steel shim clamps can be used *in
> some circumstances* but my understanding from Polyphaser folks was these
> are not to be used as primary grounding clamps for heavy conductors.
> These are just to attach some kind of light-duty strap or wire (or
> braid!) to a galvanized pipe, tube, or rod. For the main ground
> connection that is intended to handle the lightning surge, you have to
> use the heavy-duty clamps.
>
> A good source of information is usually an electrician or tower
> installer who knows what the local codes are and any special
> circumstances that require particular hardware, coatings, etc.
>
> 73, Ward N0AX
>
>
> On 10/16/2017 11:13 AM, Billy Cox wrote:
> > 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
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
>
> _______________________________________________
>
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