[TowerTalk] Battle of the bearings

[jimlux]

N4NW wrote:
> The problem with the bearings you indicate is that they are not 
> 'thrust bearings!"
> 
> A thrust bearing is a particular type of rotary 
> <http://en.wikipedia.org/wiki/Bearing_%28mechanical%29>bearing. Like 
> other rotary bearings they permit rotation between parts, but they 
> are designed to support a high 
> <http://en.wikipedia.org/wiki/Axial>axial load while doing this.
> 
> 73's
> Tom - N4NW


true. but I think most "ham" thrust bearings are regular old radial load 
ball bearings with the races parallel to the shaft. A standard bearing 
will take a fairly substantial axial load, and the rotation rate and 
duration in an antenna application is miniscule compared to any normal 
shaft sort of application.  The rotation rate is what? a few RPM?

In fact, it might be that the radial load is higher than the axial load 
in ham applications.. put a long mast with a big antenna on it in the 
wind and you develop a fairly high radial load. The axial load is just 
the weight of the mast and antennas... a few hundred pounds perhaps, 
which is pretty small for a bearing that is taking a 2" shaft, no matter 
how the balls and races are arranged.

For ham applications, a decent BUSHING made of something like HDPE 
that's UV resistant might be as good as anything else. A half inch thick 
sheet of HDPE (aka a plastic cutting board) would be a good start.