[TowerTalk] HyGain Crankup Tower HELP

[Doug Rehman]

> McMaster Carr has sheaves.  You can get them with bronze or 
> even sealed ball bearings.  For the 1/4" cable, they are only 
> 2" diameter however.

I would be very concerned about using 2" diameter sheaves for 1/4" wire
rope. It's been a little while since I researched it, but I believe the
minimum recommended size is around 4.5" or 5" for 1/4" wire rope.

There is an email in the archives
(http://lists.contesting.com/pipermail/towertalk/1998-January/011959.html)
where someone replaced 3/16" wire rope on a crank-up with 1/4" wire rope.
The 1/4" wire rope failed prematurely (after a year or two). He examined the
failed wire rope in a lab and determined it had been prematurely weakened by
running over pulleys/sheaves that were too small. 

Doug
K4DDR