[TowerTalk] New Sheaves for Crank-Up

[n0tt1 at juno.com]

> I'm in the process of refurbishing an old EZ-Way crank-up and 
> looking to replace some lift cable sheaves which have excessive wear 
> in the ID of the groves. The current 3" OD metal sheaves are sized 
> for 3/16" cable. The sheaves are rather narrow, measuring 0.38" at 
> the rim and 0.45" at the hub where the ball bearing is pressed in. 
> The tower sheave brackets will only accept a maximum sheave width of 
> 0.50", and that's tight. 
> 
> While looking at McMaster-Carr's web site ( 
> http://www.mcmaster.com/#wire-rope-sheaves/=o71onb ), I was 
> surprised to see Nylon sheaves for wire rope applications. For the 
> size I'm looking for, they have the same load rating as the metal 
> sheaves shown near the top of the web catalog page. 
> 
> Does anyone have experience with using Nylon sheaves in the lift 
> systems for crank-up towers? Somehow, this seems wimpy to me, but 
> they do meet my max width requirements and have the same load 
> ratings as similar sized metal sheaves.
 
I have a old EZ-way tower (RBX-50) and NO WAY would I
use any kind of plastic/nylon pulley on that lift system!!!
Sure, the nylon might carry the load when new, but nylon
eventually will get brittle in sunlight/WX and fail under
the load. 
 
Just my 2-cents worth.  :D)
 
73,
Charlie, N0TT