[TowerTalk] Foldover calculations

[David Hachadorian]

----- Original Message ----- 
From: "Mike Bragassa, K5UO" <bragassa at consolidated.net>
To: <towertalk at contesting.com>
Sent: Tuesday, January 10, 2006 1:06 PM
Subject: [TowerTalk] Foldover calculations


> Need the calculations / methodology  for how much tower can be added 
> for the Rohn 25g Foldover. Cannot locate in my Rohn catalog.

Specs show 32.5' below the hinge, and 35.5' above the hinge, for a 
total of 68'. At that height, the safe weight at the apex is 100 
pounds, which means that the max allowed moment about the hinge is 100 
x 35.5 = 3550 ft-lbs. If you try to add one more r25 section at the 
top, that would add 40 pounds at a distance of 40.5 ft, which would 
produce a moment of 1620 ft-lbs, which would be ok, leaving 3550 - 
1620 = 1930 ft pounds margin.

If you added another section, it would be another 40 pounds at 50.5' = 
2020 ft lbs, so you would be over weight.

Even with only one section added, you would need two guy levels above 
the hinge, because you can't have 40.5' between guy levels with r25.

Apparently, from horror stories I've heard, there is not much of a 
safety margin on these foldovers. Weight at the top is a limiting 
factor.

Dave Hachadorian, K6LL
Yuma, AZ