I'm 5'7" and weighed somewhere around 150- 160, give or take (It's been
quite a while) and I'm nowhere near being a paragon of strength,
although I was in good shape. My limit was benching 150#. Military
Press was only a bit over 100#. So, yes, I did weight training, but my
limits were quite modest. Walking the 40' steel tower (25G) up was not
difficult, although it was work. No, I would not have been able to do
it with even a small, 3L tribander mounted.
50 feet took a crew along with the aid of two on the roof guiding a rope
to a couple in the driveway. So a little made a big difference.
By the figures below, I don't think would have been able to raise a 40'
25G by myself.
73
Roger (K8RI)
On 3/20/2015 11:57 PM, Richard (Rick) Karlquist wrote:
On 3/20/2015 5:20 PM, Bill N6MW wrote:
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
I worked out all those calculations and didn't assume perpendicular.
It turns out that the walker should tilt forward at an angle that is
half of the angle of the tower. Thus as the tower goes from 0 to 90
degrees, the walker tilts from 0 to 45 degrees. The worst case force
occurs at slightly more than half way up and amounts to 1.7 times the
weight of the tower for a 40 foot uniform tower. The 1.7 factor
assumes that the walker can somehow always be at the optimum tilt
angle. In the real world, you would have to allow for some error in
this angle, since it is not intuitive. This could increase the force
by 10% or 20% easily. For a 30 foot tower, the 1.7 factor scales
proportionately to 1.275 times the weight of the tower, etc.
It is assumed that the walker's overhead reach is 7 feet.
Anecdotal examples of a given tower being "easy" to walk up merely
describe the physical strength of the walker. I remember a
40 foot mast that two of us couldn't walk up and we got
a football player to do it for us. He did it "easily" by himself.
There are two disadvantages to the non-falling derrick. You can
only have one pull point on the tower, and that pull point cannot
be much higher than the height of the derrick. If the tower
cannot stand the strain of this lift, you have to go to a falling
derrick. I don't understand the comment about the vehicle.
There is nothing about a falling derrick that precludes using a
winch instead of a vehicle.
Rick N6RK
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73
Roger (K8RI)
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