Mike Rauh wrote:
> Hello TT:
> How does Rohn compute the guy rod angle? I tried taking the vector sum of
> the guy pretension. That gives an angle that is too low. I didn't consider
> sag; if I did, the angle would be even lower. What gives?
> Mike Rauh, NV7X
I didn't see any responses to your question so I will offer one.
In general, Rohn does not tell anyone how they calculate anything, unless, of
course, your are willing to pay for that service. You might want to ask them
directly, but don't hold your breath waiting for the answer . . .
There is a page in the latest Rohn Consumer Catalog (page HA80) that discusses
guy anchors and some specifications about installing them. It does say that guy
rod slope must be within + or - 1 degree but they neglect to tell you within 1
degree of WHAT or how to determine the ideal slope. Even if you knew the ideal
slope, how could you measure within 1 degree of it in a typical tower
installation? Is it really THAT important . . . ?? I think this is just
another Rohn "escape clause" in case your tower comes down and they want to pass
the responsibility buck back to the installer . . . but then that is just my
personal opinion . . .
I just take a look at the situation on paper (neglecting guy wire sag) and
estimate the average slope of the guy wires to ground. I install my anchors so
the rod slopes at the about the average of the guy wires, as close as I can get
it. Has any tower failure EVER been attributed to guy anchor rod slope being
off a few degrees? In 48 years of hamming, I have never heard of one. Yes,
guys and anchors fail but not because the rod slope is wrong (unless it is WAY
WRONG, like vertical elevated anchor posts, and even then, with proper design,
you can elevate your anchor points just fine).
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