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

[Roger (K8RI) on TT]

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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