My 140' Rohn 65 base is 4x4x2 ft. PE engineered. So 3' of concrete is a
bit much, check the Rohn catalog. The most important thing with a base
in concrete is the legs go through it and into some gravel for
drainage. I've seen many legs split by water freezing in them.
I wouldn't go as far as "3/4 ply and broomsticks" but the loads from 30'
won't need much of a base for 2000psi soils. It's all in the catalog.
Grant KZ1W
On 1/29/2015 10:10 AM, Wilson wrote:
I think you are being led around by the short hairs.
How did you decide a 27’ tower needed to be in 3’ of concrete?
For practical purposes there is no bending and no horizontal load at the base of this
tower, assuming it is guyed, of course, which –25 must be.
You could stand 30’ of 25 on a piece of 3/4” plywood and three broomsticks and
have a fine installation!
The guywire and anchors are your real design hotspots, so a reasonable estimate
of overturning moment is necessary.
With it, you figure the worst guyline load and that gives you an anchor
capacity requirement.
You may have the perfect place for some screw in anchors, or an ideal place to
display some heavy yard art!
Yes, you’ll have a little horizontal load due to drag on the tower itself, if
it’s in the clear, so maybe use rebar or pipe instead of the broomsticks.
I have a 2’ square pad and a tilt plate for mine (40’) and it’s overkill. The
tilt plate is great for antenna maintenance.
And are you required to tell them all about the antennae to be installed?
The less you tell them, the better, since you’ll be changing eventually anyway.
WL
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