David Gilbert wrote:
> WA3GIN wrote:
>> "I wonder how the ball bearings know the difference between vertical and
>> horizontal loads and all the points between?"
> By the configuration and location of the races ...
As well as the bearing design, orientation, and materials. Look at the
orientation of the races and the split in the Ham series rotator. Top
and bottom races are horizontal with the split being perpendicular to
the axis of the shaft. IOW they are for support only and not side
thrust. For one that does both, look at a wheel bearing. It uses
tapered rollers aligned on an angle. Although the TB-3 has upper and
lower races the split is about 45 degrees low on the outside so side
thrust does not force the rollers into the split. Side force pushes the
ball up and away from the split. They will support a load on the
vertical axis but the materials (steel balls on an aluminum race) are
not designed to support much of a load or a good combination to do so.
Put a heavy load on them and the balls will "roll" flakes of Aluminum
off the races. There's a name for the phenomena but I don't remember
it. The best I've been able to get is about 2 to 3 years out of a
TB-3 before the top race is riding right down on the base casting. I
hasten to add, changing out a TB-3 at a 100 feet with over 800# of
antennas and mast is quite an experience (Read lots of work). That is
why I'm replacing the TB3s with DOM sleeves. I think I may try double
oil quenching those sleeves to get a hard surface that will wear
better. What I should do is fit them with Delrin sleeves for bearings.
Oil quenching does two things. The rapid cooling of the surface makes
it hard, while some of the carbon in the oil goes into the steel making
"the surface" high carbon steel. Water quenching makes the entire piece
hard and thus brittle.
How well does this work? A few years back I was shooting at some
silhouette targets with a 9mm. I should have inspected the targets
before starting but didn't. Some one had used a high powered rifle on
the one target and left quite a crater. One 9mm shot went in the crater
on one edge and right back out the other which resulted in it coming
right straight back and got me in the right leg with a lot of force just
scraping the outside of the shin bone. One inch to the left and it would
have busted my leg. Fortunately I was standing at a slight angle and
only lost some hide although it felt like I'd been hit with a baseball
bat. Also fortunate was we were shooting at what would be a fairly long
range for pistols rather than at the typical 25 feet.
I took the targets home and used them as patterns to make new ones out
of 1" thick steel plate which I oil quenched after fabrication. Those
high power rifle bullets only left skid marks on them after that. They
would shatter water quenched targets. BTW these were animated targets
that would move when hit, *sorta* like the ones you see at shooting
galleries, but designed to handle a lot more power. (and a lot heavier)
>> "Always fun to read the various post on this reflector."
> That's for sure ...
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