John, try a google search for 4130 chromoly specification. Several hits
will come up.
Beware that the material is usually sold without the final heat treatment
and to reach the yield strength you are looking for, this final step has to
be done.
Your steel supplier should be able have this done or at least let you know
where you can have it done.
You will have to decide just what yield strength you are looking for. Too
little and the tubing can bend; too much and the tubing can shatter under
maximum stress. In our applications, shattering tubing is not good since that
would allow the antenna to free fall to the ground.
100,000 to 110,000 yield numbers seem to be a good compromise. You may find
that using larger diameter tubing with a more commonly available yield
strength may be more economical in the long run.
73,
Gerald K5GW
In a message dated 7/14/2009 5:05:38 P.M. Central Daylight Time,
john@airwave.ie writes:
Folks,
Last winter, I had a stack of a 40m full size beam and a tribander wiped
out
by a storm. The point of failure was the steel tube that I was using which
bent over and caused a knock on affect which destroyed the beams. We have
learn the difference between pipe and tube the hard way.
There are several steel stockists here in Ireland, but they only carry
standard galvanised piping. I have checked the towertalk archives and there
is a lot of discussion there on the merits of Chrome-moly tubing and the
different grades that would be suitable for this type of installation.
However, these seem to be US standards and the steel merchants here are not
familiar with them.
Can anyone point me in the right direction ? If someone has purchased
tubing
for a similar project, I would be very grateful if you could send on
details
of what tubing you have used.
Regards
John ei8ir
For EI7M Group
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