[TowerTalk] Cadweld vs other welds or brazing

[David Gilbert]

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.

Although I have solid copper ground wires cadwelded to the base section 
buried in the concrete foundation, I was reluctant to risk the annealing 
action that MIGHT occur on the tower legs above the foundation, so the 
additional ground wires that I fastened to those legs (I wanted to be 
able to demonstrate after the fact ... if needed ... that the tower was 
grounded)  were done mechanically.  I used half of a galvanized pipe 
ground clamp and bolted it to the tower leg, attached the ground wire to 
the wire lug, and then spray painted the entire connection with 
galvanizing spray.  No hassles, no worries.

73,
Dave   AB7E




On 4/26/2014 2:05 PM, Roger (K8RI) on TT wrote:
> On 4/26/2014 1:00 PM, Warren Wolff via TowerTalk wrote:
>>   My Tower guy wants to CadWeld my copper to the
>> legs of my AN Wireless tower.  This worries me.
>
> I'd pass on CadWelding directly to tower legs. CadWelding melts a goof 
> portion of the base metal and alloys it with the copper and the 
> Aluminum in the CadWeldinf material.  It makes a very good electrical 
> joint, but would severely weeked the portion to the legs that is 
> melted. It also heats quie ab=n area areound the weld to red hot, 
> which slowly cools.
>
> I don't know the temper of the legs, but any present temper is likely 
> reduced.    I would neither heat the legs to a temper reducing dull 
> red, or hotter, nor would I allow holes to be drilled the the legs and 
> particularly no holes in galvanizing. ROHN specifically warns against 
> drilling out tight fitting bolt holes, or using the bolt to thread its 
> way in. To enlarge the holes, use a long taper pin with a gradual 
> taper. This will open the hole enough to allow "sliding" the bolt in 
> and leaves the galvanizing in tact! You may have to drive the taper 
> pin in from both directions.
>
> As a general rule, for tower legs, don't heat, don't weld, and don't 
> drill.
>
> 73
>
> Roger (K8RI)
>
>>
>> Warren
>> W7WY
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