[TowerTalk] New Sheaves for Crank-Up

[Patrick Greenlee]

I have seen Nylon pulleys with wire used on small sailboats with low stress 
on the pulley but never in a high stress application.  I too would be 
concerned with UV degradation with lengthy exposure.  Aluminum alloy with 
wire rope is as chancy as I would want to go.  My preference is steel 
wheels, preferably stainless.

YMMV

Patrick AF5CK

-----Original Message----- 
From: Grant Saviers
Sent: Friday, August 23, 2013 8:00 PM
To: N3AE
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] New Sheaves for Crank-Up

No experience with wire rope on nylon, but you might consider the UV
degradation of nylon as a drawback, particularly since one segment of
the sheave is exposed for long periods. (assuming you leave your tower
up most of the time).

Did the ball bearings seize up and cause the excessive wear?

Grant KZ1W


On 8/23/2013 5:43 PM, N3AE wrote:
> Hello tower experts,
>
> 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've found another source that has what I need in stainless steel (with a 
> bronze bushing rather than a ball bearing), but still curious about the 
> Nylon.
>
> Thanks
>
> Shawn - N3AE
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