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
************************************** See what's free at http://www.aol.com.
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|