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@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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