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[TowerTalk] Crankup towers -Reply

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Subject: [TowerTalk] Crankup towers -Reply
From: (Kurt Andress)
Date: Fri, 12 Jun 1998 22:01:48 -0700
> However, my crank-up manufactured by ALUMA-TOWER uses stainless
> steel cable.  BTW, the cable does not support the sections once the
> tower is cranked up.  There is a rotating SS block controlled by a pull
> cable that rotates out of the way while the tower is cranked up, and then
> rotates down under and under a horizontal rung on the second section.
> When the tower is then lowered slightly, there is a notch in the block
> cradles the rung and takes the weight off the cable.  There is also a
> second cable on the winch that functions as a positive pull-down.
> Jim              W4LC

This explains the type of "Cranky" towers that can be guyed. They are the
ones with positive locking systems that transfer the vertical loads from
section to section, without loading the pullup cable. If you can't lock off
all sections and let the cable go slack, don't put guys on it!
Tower guys do a great job of reducing the lateral bending moments on the
tower. Since, you never get something for nothing, realize that the way
that guys reduce the lateral loads is by converting a significant portion
of them into vertical loads that try to push the tower into the ground.
If your tower manufacturer has not provided positive locks and says you can
guy the thing, he has provided you with oversized pull up cable. This means
that you need to pay careful attention to the condition of the cable.
The reason Stainless steel cable is not recommended is because it is not as
strong as the galvanized steel wire rope. Remember that 300 series SS has
the same yield strength as aluminum. 
No kidding!
73, Kurt

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