[TowerTalk] crank-up tower safety

[Al Williams]

My just posted message wasn't completed--I cliked on "send later" thinking
that the computer would put the message in a place where I could retrieve it
to finish.

The next question.

The tilt-raising cable is at an angle of 23 degrees from the plane of the
tower. Is the required force along the plane of the cable to lift the 900lbs
equal to 900/.39=2308 pounds (900/sin 23degrees)?

With a 2:1 mechanical advantage of the pulley the force is reduced to 1154
pounds assuming 100% efficiency of the pulley.  The specification for the
winch max load is 1500 lbs for the first layer of the cable on the pulley
and 700 lbs for the top layer.  With the amount of cable furnished by Triex,
the winch was just beginning the third layer.  I estimate that the winch is
capable of about 10 layers.  At the third layer, the max load calculates to
about 1260 pounds.  This is very close to the required force and the force
required to
overcome the loss in the 2:1 pulley has not been included.  There is another
pulley in the
tilt-raising cable that wraps around all but about 85 degrees of the pulley
for another loss.

This ends the safety question but I have another question.

The winch specification claims a 41:1 max mechanical advantage.  The 1154 lb
force
required should be reduced to 1154/41 = 28 pounds.  This is far from what I
had to use.
The winch uses a 5.1:11 gear ratio.  The gear teeth are approximately at a
radius of 3/4" and the winch handle is 11 inches long.  (11/.75)(5.1)=74.8
which isn't too far off from
their 41:1 considering the guess at 3/4" gear radius.

All comments will be appreciated--This is a great reflector!

k7puc



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