[TowerTalk] Bearings for Axial Load

Grant Saviers grants2 at pacbell.net
Sat Jul 15 22:42:29 EDT 2017

Agree 100% for top of tower mast restraints - use a UV resistant plastic 
or paint it.  UHMW is cheap and almost as slippery as TFE, HDPE/LDPE 
slightly more $ and friction, Delrin/acetal even more $ and friction 
(still low) but a dream to machine, nylon in the ballpark of acetal.  
Most plastic cutting boards are HDPE or LDPE, stack a few.

However, for the bottom bearing of a rotating tower, it probably gets to 
a pretty large piece of plastic and careful engineering to handle the 
load - could be 40,000lbs thrust.

The spherical roller bearing spec request that started this thread is 
rated a 65k# radial but so far no post has offered its axial spec, and 
most likely it will be less than the radial limit.  I did find an SKF 
spherical roller thrust bearing in about the same size (2.9"id) and it 
was rated 135k# thrust.   A different animal, however.

I suspect the RTS bearing is ok for 55G since the max leg compression is 
about 18,000# plus a safety factor.   But specs are lacking for the 
bearing.  One issue I've been told about with rotating towers but never 
done or seen done is how to replace the bottom bearing without taking 
the tower down.

Grant KZ1W

On 7/15/2017 9:57 AM, Charles Gallo wrote:
> This whole thing brings me back to one of my hobby horses.
> Why are we using ball/roller/taper bearings for this use?
> A nice hat section (inverted) plastic bearing (cheap if molded, more expensive if machined due to waste) made of say nylon 66, or even Teflon (particularly if filled) would be way better. They won't fret from vibration, never need lube, designed right won't see sunlight, never corrode , and would probably be less expensive in production quantities (see molded). I could build something that doesn't use solids, but multiple pieces of rod ends that would have more labor, but less material cost
> Ball/roller bearings are great, but are really the wrong thing for an intermittent duty, low speed, weather exposed, hard to maintain environment, with vibration and shock when stopped
> --
> 73 de KG2V
> Charlie
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