[TowerTalk] Lateral Forces on Tower Base?

[George T. Daughters]

hi all,

do a thought experiment with me.  imagine a 50 foot tower, guyed part 
way up, say at 25 feet. the guys are absolutely perfectly 
equally tensioned, and not stretchy.  (remember, this is an 
imaginary tower)  now say that there is a big antenna at the top.  
now let the wind blow.  as others have already pointed out, there 
will be lateral forces at the base from the wind on the base sections 
(the bottom 25 feet) but there will also be much larger lateral 
forces (in the opposite direction to those arising from the base 
sections) due to the big antenna and the top sections of tower.  it's 
like a lever with the fulcrum at the guy level of the tower.

if anyone doubts this, i suggest the following REAL experiment:  
build a tower about 50 feet high, guyed at 25 feet, with a big 
antenna on top, and a  free-floating, well-lubricated base...  
say a smooth steel plate on dry ice.  build this installation more 
than 50 feet away from anything you care about.  now, when the wind 
blows (even a gentle zephyr) DON'T stand anywhere near the thing.  
the lateral forces at the base will kick the base out (toward the 
wind!) and the whole works will come down!

sorry... a long winded, but i hope understandable, demonstration that 
there ARE lateral forces on the base of a tower.

73,
  
George T. Daughters, K6GT

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