Each of the three galvanized legs of my new tower bolts to galvanized
steel coming up out of the concrete base. There are multiple bolts per
leg. I intend to add stainless steel tabs (like a washer) to one of the
bolts at each of the three legs. The "washer-like" tab will extend out
into space sufficiently to be drilled with a pair of holes to accept
bolts which will be used to secure copper strap in a clamping
arrangement to maximize contact area. Short of using zinc strap (never
actually considered), I haven't thought of a better way to control
dissimilar metal corrosion. My experience in marine electronics has
included this sort of arrangement to good advantage and effect.
The galvanized tower will only contact stainless steel and the copper
strap (you could use wire if preferred) only contacts the stainless
steel. ...and now comes the part where experienced folks have
differed. Some use water proof coatings over all areas of contact of
dissimilar metals and some don't. Most of these applications were
seagoing and subject to salt encrustation. Fresh water rinse on the
unprotected connections was advised to the operators but as you can
imagine that didn't happen in all instances. Personally, I lean toward
coating the connections.
Yes, this is anecdotal evidence and was not published in a peer reviewed
journal specific to the area of interest. There is no warranty expressed
or implied as to the the fitness of purpose of any of the above which is
offered solely for entertainment purposes to adults except were void due
to local laws. ;) ;) YMMV
Patrick NJ5G
On 10/16/2017 6:44 AM, john@kk9a.com wrote:
I am not aware of any clamp for attaching copper strap to a tower leg
other than a hose clamp and shim. Polyphaser sells a modified hose clamp
just for this purpose. Why would the hose clamp blow apart? I have used
this method for decades and have had multiple direct lightning strikes.
John KK9A
To: Reflector <towertalk@contesting.com>
Subject: Re: [TowerTalk] Fwd: Grounding connection to tower legs (Kevin
Stover, AC0H)
From: Ward Silver <hwardsil@gmail.com>
Date: Sun, 15 Oct 2017 21:35:32 -0500
Use a proper clamp designed to connect copper wire to galvanized tower
legs. For Rohn 25, the clamp is part number R/CPC-1.25 and I'm sure there
is a larger one for Rohn 55. A local electrical supply house will also
have clamps for connecting copper to galvanized pipe. Ask for it and
follow the installation instructions regarding how to prep the surfaces
and any other cautions. If you can't get the special clamp, you can also
use bronze grounding clamps over the stainless steel shim. Do *not* use
stainless steel hose clamps - they will blow apart under the stress of a
lightning strike. You spent a bazillion dollars on the tower, protect it
with the right non-corroding materials that are rated for the job.
73, Ward N0AX
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