In a message dated 96-06-09 21:35:06 EDT, you write:
>What's the conventional wisdom on using torque arms? Are they
>really necessary? I'm building 125 ft. Rohn 45 tower guyed in three
>places with 18 sq. ft. of antenna/mast wind load. (Not sure
>of the torque due to the antennas).
Hi, Kris --
A non-engineering answer is definitely! Handling torsion forces is a
significant challenge for any tower.
1. Do what the manufacturer says; Rohn says use the guy assemblies.
2. Using Rohn's guy assemblies (torque arms) allows a secure
attachment for the guys (as opposed, for example, having them looped around
the legs where you have the forces being held by the diagonal welds).
Imagine a force big enough to pull the leg out, bending it and possibly
breaking a weld or two. This would not happen with a guy assembly.
3. The guy assemblies allow the forces to be spread across the faces of
the tower instead of just a leg. (See 'big force' above.)
4. The current guy assembly allows Rohn towers to comply with the
TIA-222-E structural tower standards. Lack of guy assembly makes them
non-compliant and probably has an impact on their rated wind load figures as
73, Steve K7LXC