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Re: [TowerTalk] Photos of a Crank Up Positive Pull Down mechanism?

To: towertalk@contesting.com, ab7r@cablespeed.com
Subject: Re: [TowerTalk] Photos of a Crank Up Positive Pull Down mechanism?
From: K7LXC@aol.com
Date: Thu, 5 Apr 2007 17:31:29 EDT
List-post: <mailto:towertalk@contesting.com>
 
In a message dated 4/5/2007 9:02:52 A.M. Pacific Daylight Time,  
towertalk-request@contesting.com writes:

>  I've also wondered about the positive pull down.  I  have 
an old Hygain manual for their electric winch (I don't 
have the  electric winch though) and it shows how to run 
the positive pull down  cable.

>  If I recall correctly, the cable runs from the bottom  of 
the 3rd section down to a pully at the bottom of the 
second section  up to the top of the second section.  This 
is repeated with another  cable from the bottom of the 4th 
section to a pulley at the bottom of the  3rd section and 
up to the top of the 3rd section.

>  How  does this create "positive pulldown" when it is still 
gravity that brings  the sections down when lowering with 
the winch?  Is it the weight of  that 2nd section that is 
being used to help pull down the lighter 3rd and  4th 
sections?
    
    Don't over-think it. It's basically a cable  attached to the bottom of 
the top section since that's the one that's  prone to hang up. The trick is 
having it pull at the same rate as the  crank-up mechanism in reverse in order 
to 
be automatic. 
 
    You could do the same thing yourself by just  attaching a cable to the 
bottom of the top section thru a pulley at the bottom  of the tower to get the 
cable to turn horizontal and then using a comealong or  another winch on it 
when it gets hung up. Not very elegant but it'll work.  Remember you'll only 
need 
it if the wind is blowing. 
 
    Building some sort of automatic way to do  presents some complications 
that you may not be able to solve. Remember the  ones that use it currently 
have 
a drum with both cables attached to it so  that they go up and down at the 
same rate. 



 Cheers,
Steve    K7LXC
TOWER TECH 



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