[TowerTalk] Cadweld vs other welds or brazing

[Roger (K8RI) on TT]

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.


>
> 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)

As long as the ground wires do not leave the concrete below grade. That 
is often specified in code and/or tower specs.

73

Roger  (K8RI)


> 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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