[TowerTalk] Rohn 25

[Hank Lonberg]

Blake:
I beg to differ with you.

Using TIA/EIA 222-F wind loading criteria and 70 mph wind velocity (min.
recommended) a 40 foot section of Rohn, 25g un-guyed and cantilevered will
develop a moment at the base of 7200 ft-lbs at the base. This is without an
antenna load, just the tower itself. The published allowable moment for 25g
,by Rohn, with a 1/3 increase for wind loading duration is 6,720 ft-lbs. At
40 feet it is clearly overstressed. How do you say that this is ok and that
Rohn fully supports this?

Regards
Lonberg Design Group, Ltd.

Hank Lonberg, P.E.,S.E. / KR7X
President

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Blake Bowers
Sent: Saturday, January 29, 2005 12:53 PM
To: TowerTalk at contesting.com
Subject: Re: [TowerTalk] Rohn 25

Actually, Rohn fully supports the R25 up to 40
feet as a self support.    

Aside from that however, 60 feet they do not support,
and supporting an inverted V would be an absolute 
no-no.  

I have seen R25 at 60 feet self supporting a lot 
however, and they do fine, again without an inverted
V pulling on it.


> I'd guess about 12 feet :)
> 
> The 25 isn't designed to be free standing, though I've seen them up to
> 30 or so with no real trouble if the base is good.  
> 


_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.

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