It is a little hard to say without seeing a sketch of what you are
talking about. I would consider tapered roller bearings for that
application, since I think that you would have substantial thrust on the
bearing. (The thrust would be the 400 pounds plust he weight of the
arm.) I would be tempted to use a tapered roller bearing top and bottom.

One possible concern would be that the whole thing would move too
easily, that it would swing when you did not want to, especially if the
pivot was not exactly vertical. This would be more likely with ball
bearings than bushings. With 400 pounds you could probably dispense with
bearings altogether, and just use bushings. You could use a bushing
with a shoulder as a thrust bearing on the bottom, and a regular bushing
on the top. This should be relatively non-critical in terms of assembly
tolerances. A self-lubricating bushing could be a simple and inexpensive
answer.

How can you support the whole thing on one bearing? Wouldn't you need
an upper bearing and a lower bearing?

Somebody will probably answer who knows how commercial cranes of that
type are made. I make no claims to being an expert on bearings.

Richard


Steve B wrote:
I am going to put about 400# on the end of a support that I want to swivel.
I figure I am going to use a #8 grade bold in a vertical position. This
will rest on one ball bearing.

I have seen these ball bearings used in weld on hinges for large wrought
iron gates. The weight rests entirely on these bearings, and there is a
zirk fitting.

What hardness are the ball bearings? Do you think the combination of the
two would be a lifetime application? I think this would be a very workable
thing, even if I just use a hinge intended for wrought iron use, and mount
the vertical shaft one or two inches offset, just to get it to ride on the
bearing.

It's for the bottom pivot point for a davit hoisting mechanism.

Thanks.

Steve




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