That is a strange design. It will work if you use spherical ball joints, but even then it will tend to rip them out when the arm bangs on the post, which it will tend to.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
For spherical joints, I recommend GM Part No. K5208. These are upper ball joints and are easily available from Chevrolet. Tell Jimmie that Bob sent you. He owes me another ride.
Ps.: Your arm is not rotating about a vertical angle.
pps. If you can find a ring bearing for the lower mount, we can fix you up with a hub unit bearing for above, GM Part No. 1585 1077
This jib crane is self-centering. Perhaps it was intended to swing that way? You can put a shock absorber snubber on the column to stop the jib arm. I will get you a GM part number for a snubber.
You could tip the column so center of rotation was vertical ( no self centering) or with the upper end of the axis leaning slightly toward the middle of the intended working arc.
If there are (understandable ) concerns that that a leaning column would look "weaker" or just goofy, then offset the upper pivot to accomplish the same thing.
Is the intent that the upper bearing will handle all the vertical load? Realistically only one bearing will handle the axial load anyhow.
The load/reaction arrows are pointing in directions that confuse me.
What are the magnitude of the reactions, and how often and how far will the arm be pivoted??
Jokering:
As mentioned above, the centers of rotation of the two different sets of bearings should be on the same vertical axis, or you get some very funny/difficult forces/reactions and motions of the boom. You would be better off making the vertical axis of the lower bearing the common axis, and moving the top bearing to the left, onto that axis. Then, you need a thrust bearing at one of the two locations (top or lower reaction point) to pick up the vertical loads.
Alternatively, you could leave the top rotational bearing at the top/center, add a thrust bearing for vert. loads. Then, at the lower location add a reinforcing/running ring to the column o.d. and use two cam rollers 15 or 20̊ each side of the boom center line, to pick up this horiz. reaction and keep the boom centered on the column.
Google ‘jib cranes,’ there are many manufacturers/designers of these cranes and there are many minor variations of the general theme. Some of the variations will have to do with exactly what you are trying to accomplish, with this crane, in you design/plant.
Do you mean the lower bearing? Well, I just happen to have some idler pulleys mounted on ball bearings that are just right for your application. I recommend the ones without the tensioners and with the smooth face designed for running on the backs of the multi ribbed belts. Jimmie uses these; I will get the part numbers if this is what you had in mind?
For the top bearing, I rest my case with the hub unit bearing recommended previously. It has axial and radial capacity.
Did I miss what the design loads are?
10s, 100s, 1000s, or 10,000s of pounds?
I think some capacity for static and even a little dynamic misalignment is required for the upper bearing, and probably the lower rollers as well.
Hence O'brien's use of a spherical roller for their upper bearing ( fully self aligning) , and the crowned rollers (to prevent edge loading) for the lower.
If none is provided, the mountings, housings, and even the bearings themselves may be sorely taxed, from which no good can come.
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