>I don't recall the conclusion of the discussion on Rohn joint bolt kits
>of late. However, I did have occasion to purchase "real" Rohn JBKs for
>some 25 tower yesterday, and I can confirm that the nuts and bolts they
>now supply are NOT galvanized. They seem to be generic cad plated
>hardware. The last time I bought some "real" JBKs, they were galvanized.
>
>I supposed that is progress...
>
>Jim N6IG
It matters whether you are buying 25JBKs or 45JBKs. The ones for 45G are
galvanized. This has been the status on these bolts for at least the past 2
years. Seems it was the same back in the mid-70s as well, if my memory
serves me correctly . . .
I see in some other posts that we are getting our terms a little confused.
Webster tells me that "galvanizing" is a process of coating iron or steel
with molten zinc. I have also heard of this as "hot dipped galvanizing" and
I have actually observed the process. Quite interesting to watch. Anyway,
Rohn tower sections are hot dipped galvanized and so are the bolts for 45G
and larger tower.
"Plating", on the other hand, is usually an elecrical process where one
metal is deposited on another one forming a protective coating. Usually, on
bolts and nuts, cadmium is plated over steel. I believe that is what we see
in the Rohn 25G bolts and nuts but I don't know for certain that the plating
is cadmium.
My experience has been that hot dipped bolts and nuts seem to last a lot
longer than cadmium plated ones when it comes to resisting rust. I believe
the reason why 25G bolts are not hot dipped galvanized is because the
threads are too fine. The molten zinc would tend to fill the threads and
the nuts would not work very well. Normally, bolts and nuts to be hot dip
galvanized have deeper and rather coarse threads cut into them to allow for
some filling by the zinc. The tolerances are not nearly as good for hot
dipped bolts and nuts as for plated ones since the electrical process of
plating is much more controllable than the dipping process.
Some one recently posed the question as to why the Rohn 25 bolts were fine
threaded and I don't ever recall hearing the answer to that question. If we
knew there was a good reason for that, it would probably explain why they
use plated instead of dipped bolts and nuts.
There is another process for getting zinc onto the sruface of steel bolts
and nuts but I have only heard of it being used at one place. There is a
tower company in Salem, OR called Microflect and they have developed a
process for coating large steel bolts with zinc by putting them into a large
drum with powdered zinc and a bunch of hard ball-bearing-like steel balls
and rattling the whole works around for a while. The result is amazing!
Beautifully coated bolts with a very smooth and even finish. I don't know
how small the hardware is that they can use this process on. 25G bolts may
be too small. I have only heard of this process so I may not have the
description completely right. I have seen the finished bolts, though, and
they are beautiful. I suspect they are COSTLY! Microflect makes huge
broadcast towers and I have tried to talk them into making sections that are
compatible with Rohn 25G, 45G, 55G, etc. They aren't very interested. They
biggest objection they have to doing it is liability. They see us hams
mixing Microflect and Rohn sections, which I am certain we would do. They
then see a tower composed of mixed parts failing and them being sued even if
the failure was a Rohn part. So once again, a good company will opt out of
helping us because the judicial and legal systems make the process simply
too risky. (Lots of my personal comments about the legal system edited out
here . . . )
Stan w7ni@teleport.com
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