[TowerTalk] FW: UST Sheaves

[Matt]

I have serviced the bearings in several of my crank-ups for the last 15
years by drilling a small hole in the side shield of the bearing just large
enough to allow insertion of a grease gun needle fitting - essentially a
hypodermic needle with a grease fitting on it.  I think they sell them at
auto parts stores to refill things like CV joint grease boots without having
to disassemble the joint.  Anyway, I just remove the pulley, pump the
bearing full of new grease till the old grease all squeezes out around the
perimeter of the side seals, clean up the mess, and reassemble the pulley.
In the case of older bearings that have become stiff, I flush them out
thoroughly in the parts washer first while working the races and they loosen
up pretty quick.  The side seals are not 100% effective which allows solvent
to get inside and thin the grease.  I also flush the bearings out in the
washer after drilling the needle hole to remove any metal shavings that may
fall to the inside of the seal.  Just be sure to pump the bearing full of
grease after washing with solvent. 

Hope this info is useful and good luck.

Matt
KM5VI



-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Bob
K6UJ
Sent: Thursday, September 01, 2016 10:03 AM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] UST Sheaves

That's interesting.  With the correct selection, possibly lifetime
bearings..........
I would love to have sheave bearings with a little grease fitting so I could
grease them as I do the other grease fittings on the tower.   We 
discussed this
in the past but couldn't come up with anything.  After replacing two sheaves
after they froze up I would like to improve the stock design if possible.

Bob
K6UJ


On 9/1/16 6:36 AM, charlie at thegallos.com wrote:
> <snip>
>> Will take them to my local machine shop and have new waterproof 
>> sealed bearings pressed in as we discussed earlier.
> <snip>
>
> I sort of worry about the idea of any kind of ball/roller bearing in what
> is basically a static situation
>
> One of the big issues they found in cars was there was more damage done to
> a car's wheel bearings when shipping them on trains than actually running
> them.  The vibrations/shock on the bearings in a fixed location caused all
> sorts of issues
>
> Believe it or not, in intermittent motion use (we aren't constantly
> cranking our towers up and down), Bronze bearings can be great BUT you
> have to keep them lubed!!
>
> What is often used today, and properly designed is probably the best is
> some of the exotic  PLASTIC bearings.  Going to one of the thin wall
> plastic bushings can give you GREATER load without creep, and will NEVER
> have to be lubed.  Think of it as "reinforced Teflon", but some of the
> plastics are way better than that, all the way up to things like
> torlon/vespil etc (which are insanely expensive)
> If you are going to get a Sheave re-bushed, I'd look into some of the thin
> wall plastic bushings out there, and then bore the bronze to just fit the
> new bushing in there, and run that.  Never need lube, picking the right
> product, and you'll never have an issue
> (Picking the right product = knowing the load on the bearing - so if you
> know the weight of the tower/antenna etc and the diameter of the
> bearing....)
> Look at igus.com (just first I found )
> Heck, depending on load, something as simple as acetal (aka delrin) or
> glass filled/reinforced acetal is probably enough (or even glass/Molly
> filled nylon)
>
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