[TowerTalk] Cadweld Question

[Mark Robinson]

Subject: Re: [TowerTalk] Cadweld Question


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>>I was looking at the Cadweld procedure and was wondering if it is possible
>> to use my oxy-acetylene torch to heat up the cadweld material instead of
>> messing with pyrotechnic chemicals.
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> That's the nice thing about CadWeld (TM). They are neat, easy, and clean. 
> They are safe to store and safe to use when the directions are followed.
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>> What is the base material that they use to join the rod and copper wire?
>> Maybe I could just braze them together using a brass filler rod.. Any
>> thoughts on this?
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Roger wrote:-

> I have on occasion brazed cable to ground rods, but it  takes a lot more 
> skill than CadWelding. I'd pick CadWeld any day over brazing.  Unless you 
> have plenty of experience with a torch I'd stick with the CadWeld.
>
> For brazing the cable needs to be absolutely clean with solid copper being 
> much easier than even coarse stranded. With coarse stranded you first need 
> to fill the stranded cable with the brass to a bit either side of where 
> the joint will be made.  Then heat the top of the ground rod and apply 
> enough brazing rod to completely coat the top.  Then the brass filled 
> cable. Use lots of flux and get the brazing rod in as early as possible. 
> Due to the thermal conductivity of the copper it's not unusual to see most 
> of the brass *fall* out of the cable just as it starts to bond to the 
> ground rod.
> At this point it is very easy to burn the copper which makes refilling 
> almost impossible.  In addition you need to have the proper size tip on 
> the torch for the size cable and ground rod.  Being different material the 
> ground rod and cable heat at different rates, different thermal 
> transmission, and different melting points. The copper, due to the thermal 
> tranmission characteristics takes more heat, but it also melts far easier 
> than the steel. In addition the melting point of copper is not all that 
> far from brass, relatively speaking. So, you end up trying to braze the 
> brass filled copper to the steel ground rod without melting the brazing 
> out of the copper in the process.
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> With solid copper, using lots of flux, heat and wet the cable with the 
> brazing material. Wet the top of the ground rod in the same manner, then 
> with a bit of practice join the two brass covered surfaces and fill any 
> gaps with brazing rod.
>
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Maybe I should cut a rod down and practice attaching a short length of 
copper wire and see how it goes.

Would wrapping with wire and or clamping and soldering be a better bet than 
brass brazing?

Mark N1UK G3ZZM