On 8/23/2013 8:43 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.
This is probably more for others than the original poster:
As others have well stated the life problems of Nylon, my question is
why do you want to replace the sheaves? Are they bad, or just the
bearings, or do you want to replace them with something more substantial?
If the sheaves are OK, but the bearings are in poor shape, I'd just
press them out and new, sealed ones in. I assume the originals are
sealed. Changing them only takes a small arbor press. For those not
familiar with pressed bearings, they need to be pressed in and not
tapped in with a hammer. You can do it, but risk damaging the sheave
and giving it a permanent wobble.
Brass was mentioned, but it's usually "Oil light" which is a porous
Bronze, not Brass. If the axle is a good fit and smooth these last
quite well even with an off center load as long as the off axis is not
extreme. OTOH 0.45" is getting pretty narrow for much off center load.
I've never seen commercial bearings of regular brass although I'm sure
they exist. I'd not expect them to be anywhere near as durable as "oil
light", or bronze bearings which you mentioned with SS sheaves.
Unless the originals have a history of problems, I'd stick with them.
It sounds like the hub is already as thick as you can get, so you'd gain
little but appearance with a wider rim.
73
Roger (K8RI)
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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