[TowerTalk] UST Sheaves

[Bob K6UJ]

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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