Advice needed - ballbearing solution for rotating table
Advice needed - ballbearing solution for rotating table
(OP)
Hi all,
Brand new to the forum, lovely to meet you all.
I am currently undertaking a project to build a large round table composed of a series of concentric rings that all spin independently.
The basic idea is, there is a single stepper motor attached the small circle in the center of the table. The center can be spun, which locks into the other rings around them and forces them all to spin either clockwise or anti-clockwise.
Each of the rings of the table will be mounted with progressively larger arms down to a central metal 'trunk', which will allow them to all spin independently. Like those mechanical models of the solar system.
The thing I am struggling with currently is the cylindrical ballbearing solution that will allow the 'arms' to attach down the central trunk, be supported, and also spin freely. I have attached a quick exploded 3D example of the design (except the tabletop is interlocking rings, not circles). The solution I am struggling with is for the 'red' pieces in this drawing.
Any advice much appreciated!!
Cheers,
Jack Colley
Brand new to the forum, lovely to meet you all.
I am currently undertaking a project to build a large round table composed of a series of concentric rings that all spin independently.
The basic idea is, there is a single stepper motor attached the small circle in the center of the table. The center can be spun, which locks into the other rings around them and forces them all to spin either clockwise or anti-clockwise.
Each of the rings of the table will be mounted with progressively larger arms down to a central metal 'trunk', which will allow them to all spin independently. Like those mechanical models of the solar system.
The thing I am struggling with currently is the cylindrical ballbearing solution that will allow the 'arms' to attach down the central trunk, be supported, and also spin freely. I have attached a quick exploded 3D example of the design (except the tabletop is interlocking rings, not circles). The solution I am struggling with is for the 'red' pieces in this drawing.
Any advice much appreciated!!
Cheers,
Jack Colley





RE: Advice needed - ballbearing solution for rotating table
There are some great sleeve bearings made from high performance plastics (PEEK with Teflon) that might work well.
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P.E. Metallurgy, Plymouth Tube
RE: Advice needed - ballbearing solution for rotating table
RE: Advice needed - ballbearing solution for rotating table
RE: Advice needed - ballbearing solution for rotating table
Find the size appropriate here:
http://www.mcmaster.com/#standard-rolling-element-...
Note that the smallest bearing available, for a 10mm shaft, has a rated thrust load over 2,000 lbs. Including the washers (which you will need, top and bottom) you're looking at $6 per part. We don't know your budget, but I have to imagine that's cheap enough.
Each ring would be supported by a machined ring around the central shaft, which you would weld to. Inside this shaft ring you would use a plain or roller bearing, with a thrust bearing between each one to handle the axial load. Simple.
RE: Advice needed - ballbearing solution for rotating table
Ps.: I've started to use these bearings for everything.
RE: Advice needed - ballbearing solution for rotating table
This sounds really great but I'm having some trouble visualizing it... specifically the part about 'inside the shaft ring'. So the machined ring is what I weld the arms onto, and inside of that we use a plain or roller bearing which sits around the central shaft? Where does the linked rolling element bearing come into the picture? Sorry!
@Buggar - that definitely sounds more simple. You mean something like this ?
And they are ok to sustain the axial load if I attach the arms onto them?
RE: Advice needed - ballbearing solution for rotating table
RE: Advice needed - ballbearing solution for rotating table
You have several ply rings with arms
you have a central shaft
You weld the arms to a machined ring. Inside this machined ring and riding on the central shaft goes a plain/roller/ball bearing, depending on your cost and load requirements.
So if you have 5 ply rings, you will have 5 machined rings, stacked vertically on the central shaft. The thrust bearings go in between, to allow the machined rings (and thus the ply rings attached to them) to rotate independently.
I would create a drawing but I don't have the time right this minute- hopefully this explanation is clear.
Buggar's solution is similar to mine- my idea will be cheaper, his idea will have higher load capacity.
RE: Advice needed - ballbearing solution for rotating table
How do you mount the mount the machined ring to the bearing?
Think I may just buy a hub bearing for ease of use, but now I'm just desperate to make sense of your awesome solution!
Thanks so much guys
Jack
RE: Advice needed - ballbearing solution for rotating table
-design the machined ring such that the bearing is a press fit
-design the machined ring such that the bearing is a slip or light interference fit, with grooves for snap rings
-design the machined ring with a lip on the bottom of the internal bore to prevent the bearing from sliding down the shaft
Which method I would choose would depend on the load, cost target, and whether or not you expect the assembly to need to be serviced at some point. A press-fit bearing will handle more load, but will be more difficult to service if bearings ever need to be replaced. Slip fit with snap rings will positively locate the bearing and allow for very easy disassembly/service, but will be more expensive to machine because of the snap ring grooves.
Based on your description, I'm guessing that the loads this assembly needs to reliably support are small. If that's the case, I would use a small lip on the bottom of the internal bore in the machined ring, with the rest of the internal bore sized for a slip fit on your bearing of choice. Gravity will keep the bearing in place.
The hub bearing route is a perfectly serviceable way to go. Using BUGGAR's idea will ensure that your assembly is bombproof. The only advantage my concept has over his would be cost.
RE: Advice needed - ballbearing solution for rotating table
RE: Advice needed - ballbearing solution for rotating table
In regards to this most recent point about moment load and thrust bearings - does using the wheel hub bearing assembly take care of all of this? I imagine it is totally self contained and all I would have to do is mount the inner shaft onto my metal pole and then it can deal with the various stresses that will apply to it following that.
Thanks!!
Jack
RE: Advice needed - ballbearing solution for rotating table
RE: Advice needed - ballbearing solution for rotating table
ps: Jimmie Johnson lets me drive his car if I sell his parts.
RE: Advice needed - ballbearing solution for rotating table
RE: Advice needed - ballbearing solution for rotating table
One final question on the actual mechanics of the wheel hub assembly... so if I mount the inner shaft onto my 'trunk', the outer assembly which is normally what you anchor onto the wheel assembly will then spin and I can attach extension arms onto it? So all I have to do is find a decent wheel hub bearing, and then mount the inner shaft firmly and make sure it is supported and everything is golden... right? :)
RE: Advice needed - ballbearing solution for rotating table
RE: Advice needed - ballbearing solution for rotating table
My suggestion would be to use a machined part, which is pressed on or slips on around the wheel bearing, and not to weld anything to the outer bearing race. If you weld to the race, A) it will be hard to weld because the bearing race is likely a very hard alloy not selected for weldability and B) you WILL warp the bearing race, possibly bad enough that the bearing won't spin.
How big of a stepper are you using? Wheel bearings do have a fair bit of preload designed in, so they aren't super free spinning like a small ball or roller bearing is. Just something to consider.
RE: Advice needed - ballbearing solution for rotating table
Is there some reason you couldn't just put ball supports upside down on the bottom of all the concentric rings and let them all skate around on the same surface plate, separated by simple radial bearings all in the same plane?
Mike Halloran
Pembroke Pines, FL, USA
RE: Advice needed - ballbearing solution for rotating table
RE: Advice needed - ballbearing solution for rotating table
Or simply use a "lazy susan" bearing under each ring. Link
Seven different sizes here Link
je suis charlie
RE: Advice needed - ballbearing solution for rotating table
The ball supports idea is a good one too, I had considered putting the rings on a surface plate but for some reason got to a point where it didn't seem a viable option.. can't remember why though! Maybe worth going back to the drawing board...
I went to some mechanics here in Berlin yesterday and asked if they had any old wheel hub bearing assemblies ('radlager radnabers', if you're interested) and found a few. They seem like they could work quite well... is there any reason instead of welding I can't just bolt brackets into the existing holes in the frame? Where you would normally attach the assembly to the wheel. If I am locking the inner shaft onto my 'trunk', therefore allowing the outer part of the assembly to spin, I figure I can just avoid welding entirely and bolt straight onto it. Am I missing something?
Jack
RE: Advice needed - ballbearing solution for rotating table
RE: Advice needed - ballbearing solution for rotating table
No, there's no reason you can't bolt to the existing flanges, so long as your desired final assembly size is tolerant of that arrangements.
RE: Advice needed - ballbearing solution for rotating table
Seems to be heading in the right direction!!
https://vimeo.com/173743292
The board on top is just representative of the finished flush round table, I will be splitting into multiple pieces (you can maybe see the pencil marks) for the second prototype, before actually CNC cutting the rings and mounting the motor.
RE: Advice needed - ballbearing solution for rotating table
RE: Advice needed - ballbearing solution for rotating table
Only thing I am struggling with now is how to run the wiring through the center of this structure to connect the microprocessor/power supply (bottom) and the stepper motor (top). But it's getting there!!!
Would there be a better way of mounting these rather than bolts and spacers on a threaded rod? I like that because it is easy to assemble and adjust, but it makes the cable run rather annoying..
J