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[TowerTalk] Aluminum towers -- can you really "walk one up"?

To: towertalk@contesting.com
Subject: [TowerTalk] Aluminum towers -- can you really "walk one up"?
From: Bill N6MW <billsstuffn6mw@comcast.net>
Date: Fri, 20 Mar 2015 17:20:47 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Data: I had a 30' Universal Al tower weighing ~60#. Antenna + rotor was ~55#. One none too young guy could walk the bare tower alone up easily. Not true once the weight was on top. However, 2 pretty strong guys + the older guy (probably also without the older guy) could walk that up without much trouble.

Alternate: For one older guy alone the not so well know and not so famous Non-Falling Derrick method was invented to raise and lower the whole thing with relative ease. This avoids the worrisome falling derrick feature that requires you to attach the tower to a vehicle and then drive that vehicle ever so carefully (on a dusty soil hillside in my case). (http://n6mw.ehpes.com/TowerRaising.pdf)


Calculated Data (which are not data at all, of course): The calculation of the force needed to walk up a tower may not be as quite as simple as it immediately sounds. It is pretty easy to find the perpendicular-to-tower force needed to provide the moment needed to tilt the tower up given the lever arm where you are lifting (which changes with angle). However, once the tower is tilted up substantially,a force perpendicular to the tower is no longer a matter of just lifting up. The pure upward force needed then goes up like the perp force/cosine(angle) unless you can tilt your body to that angle, which you can't at any significant angle. For example with the numbers from above example, ignoring tower taper to be conservative, at 45 degrees (worst case for that perp force), and for 6' walkers, the perp force needed is 212# but that requires you to lift 301# if you just lift up (~ 2 strong guys?). Furthermore, for angles above 45 degrees the required up force steadily increases. However, once you get closer to finished you can just supply a more nearly horizontal pushing force to get the job done. For example at 75 degrees, a horizontal force of 110# will get you the needed 106# perp force since you are nearly at perp here. Just how much horizontal force a person can manage, and without having their feet slip, will come into play.

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