[TowerTalk] Cadweld vs other welds or brazing

Sun Apr 27 23:26:44 EDT 2014

On 4/27/2014 9:19 PM, john at kk9a.com wrote:
> I would not be overly concerned with corrosion from drilled holes.  The zinc
> will still protect exposed metal to some extent and you could always apply
> cold galvanizing to the hole. I have had to elongate many poor fitting tower
> accessories and I have yet to see a corrosion problem. That said, I see no

As I always have 3 taper pins to align the sections, it's faster to just 
hit them bit harder  till the bolt fits, rather than having to get the 
drill and drill motor as they are already there.
  (Using the taper pins usually saves 5 minutes or more and is easier 
and does not damage the galvanizing) I drive the taper pins in the small 
holes and the larger bolts usually just slip right in.ROHN use two size 
holes.

I also use existing bolt holes to hold ground wire clamps.

> reason to add holes when there are already bolt holes at the tower base
> where a ground lug can be fastened.

ROHN is very specific about the practice of drilling out galvanizing, or 
even threading bolts through tight holes. It could render the difference 
between insurance coverage, or not.  In the case of liability, or 
peripheral damage to your house, out buildings, or neighbor's buildings 
or injuries and that could be substantial.  Insurance companies are 
looking for more and more reasons not to pay as the industry is 
hurting.  I prefer not to give them any excuse.

Insurance companies have very long memories (records). When I lived in 
Breckenridge, I installed TV antennas on the side. It was good, easy 
money, until the main jobs left were 2 and 3 story houses with steep 
pitched roofs.  I had installed one on my own house.  They questioned 
the installation until thy found I did it for a living.

Years later, I took a Direct hit to the tower (before the ground system 
was finished. I lost a 2-meter rig, all the coax connections at the top 
of the tower, and a new computer (less than a week old). The first thing 
they asked, "Didn't we replace that antenna for you?".  I had to explain 
that was 3 houses ago, a TV antenna, and this was a much larger and more 
expensive ham antenna that was OK<:-)). The differences including what 
was a major ground system to them.  (Several hundred feet of bare #2 and 
about a dozen 8' ground rods.)  As I built the computer, I had to get a 
quote for the parts and time to build from another builder,  He charged 
more for time and parts.

I think I will stick with ROHN'S guidance, whether it's a CYA or common 
sense.  They are the manufacturer and the insurance co will likely go 
with them.

I've climbed many towers that had no corrosion but I've climbed towers 
that had only the paint holding 2 of the 3 legs holding the sections 
together as well. Only luck and fast reflexes kept me from riding 30 
feet of tower down.  They looked good, but only luck kept me alive

I did a lot of climbing until nature dealt me a bad hand, called a 
stroke.  As my left hand is only partially useful, the insurance won't 
cover me climbing, or flying airplanes any more.

I stick with the statement:

Drilling holes on thin, galvanized tubing invites corrosion. Yours is an
exception.*  I would suggest that anyone who plans on drilling, or welding to
a tower leg, first contact the manufacturer before proceeding.*

73

Roger  (K8RI)

> John KK9A
>
>
> To:	towertalk at contesting.com
> Subject:	 Re: [TowerTalk] Cadweld vs other welds or brazing
> From:	 "Roger (K8RI) on TT" <K8RI-on-TowerTalk at tm.net>
> Date:	 Sun, 27 Apr 2014 14:56:48 -0400
>
>> On 4/26/2014 10:00 PM, David Gilbert wrote:
>> I would agree with everything in that post except for the part about
> drilling holes. I own an AN Wireless heavy duty 70 foot tower, and every
> factory brace on it is held fastened to the legs >with 5/16 inch
> bolts/holes. In addition, when I purchased the tower I specifically asked
> Dan (who was then the owner of AN Wireless) what the constraints might be
> for drilling holes in the >tower legs, and his answer was that holes of the
> size normally used to receive bolts would not materially weaken the legs at
> all. It's pretty much the same physics that allow us to drill >moderately
> sized holes in floor joints and roof trusses without decreasing their load
> rating.
>
> You have a tower that was designed to allow for drilling the legs for
> braces, most tower are not and particularly towers constructed of galvanized
> tubing.
>
> These towers are designed to use a minimum of material and depend on shape
> for strength.
>
> Drilling holes on thin, galvanized tubing invites corrosion. Yours is an
> exception. I would suggest that anyone who plans on drilling, or welding to
> a tower leg, first contact the manufacturer before proceeding.
>
> ROHN specifically tells users not to drill out bolt holes, let alone, drill
> new ones.
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk