Rohn has a section in their catalog for unguided towers which includes Rohn 25.
They call for something like 2.5’ x 2.5’ x 4’ of concrete for the base. I’m not
sure I really want to be up 35 feet on that, but it has been in their
literature for as long as I can remember. I am sure many folks have built one
of these, and would love to hear opinions on ways to make it safe. I suspect
this is what the original poster was referring to. Not all of us can have tall
towers - sometimes 35 feet will have to do, and extensive guy systems can be
problematic on small city lots. So, the question really is how do we put this
stuff up and make it safe? Is this where you were heading, bcarling?
73,
Jack B, W6FB
> On Jan 29, 2015, at 8:19 PM, Roger (K8RI) on TT <K8RI-on-TowerTalk@tm.net>
> wrote:
>
> On 1/29/2015 6:57 PM, Grant Saviers wrote:
>> 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.
>
> Or use a pier pin base with solid lefs. Easy to make and not expensive.
>
> 73
>
> Roger (K8RI)
>
>>
>> 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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>
>
> --
>
> 73
>
> Roger (K8RI)
>
>
> ---
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