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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