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

Why not use Timken tapered bearings, or maybe a ball thrust bearing? Regular
ball types will not stand too much end thrust.
Walt
"Steve B" wrote in message
news:P1_vf.7134$JT.426@fed1read06...
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

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




--
http://www.fergusonsculpture.com
Sculptures in copper and other metals

Richard Ferguson wrote:

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



--
http://www.fergusonsculpture.com
Sculptures in copper and other metals

A pair of standard small trailer axle bearings should handle the load
just fine and are like $10 for numerous sources.

The problem with the ball/roller bearings is you need to somehow shield
them from the weather so they don't rust solid since they can't be
painted like the steel frame can. The ball/roller bearing will likely
also allow the thing to swing too easily which will make the alignment
more critical so you aren't fighting a tilt and any gusts of wind might
be a problem.

I still think a couple thick steel washer disks sandwiched around a
thick bronze bearing washer would be a better solution. With a grease
groove turned in the mating surfaces of the steel disks and a couple
zerk fittings tapped in so the thing can be greased it should last
nearly forever and be pretty weatherproof. It would also provide more
friction than ball/roller bearings to make the thing more stable /
controllable.

Pete C.

"Richard Ferguson" wrote
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.

The pole is 2" x 2" x .250", and is 15' long. The whole 20' piece is 91#,
plus the weight of the hoist, about 25#, then plus the load, so around 250#
sitting on the base.

The pole will have a pin coming out of each end to keep it in whatever I
finally decide to use for a mounting. I believe I can find a squarebore
harrow disc bearing with a 2" opening for the middle standoff.

I like your suggestions about a tapered bearing or a bushing. Will go to
the bearing place, and I am sure they can hook me up.

I was just looking for a quick easy way with the single ball bearing idea so
the load would sit right on one ball.

Thanks

Steve