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Advice needed - ballbearing solution for rotating table

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

RE: Advice needed - ballbearing solution for rotating table

How much load is on them? What speed?
There are some great sleeve bearings made from high performance plastics (PEEK with Teflon) that might work well.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Advice needed - ballbearing solution for rotating table

Google thrust bearings. A combination of thrust bearings and radial bearings will accomplish what you need.

RE: Advice needed - ballbearing solution for rotating table

(OP)
Thanks so much for the response guys - so I could weld supports onto the thrust bearings and have that sort of vertical weight and they would be ok? It would only be a few kilos... probably the heaviest would be a 300mm wide ring of 30mm ply at 1300mm diameter...


RE: Advice needed - ballbearing solution for rotating table

Definitely don't weld to any bearings, ever.

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

Stack a bunch of automotive hub unit bearings, each with its own extension arms.

Ps.: I've started to use these bearings for everything.

RE: Advice needed - ballbearing solution for rotating table

(OP)
Wow - thanks everyone. This is so useful

Quote (jgKRI)

"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."

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!

Quote (Stack a bunch of automotive hub unit bearings, each with its own extension arms.)


@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

No, it's more of a double flanged bearing on a splined shaft. One flange rotates and you can hang things from this. You can use a plain shaft instead of splined. I found pictures but couldn't download. I like Moog Part No. 513282; they're for Camaros and maybe too strong for your use. You can get smaller and cheaper. I have used them for children's merry go rounds and to adapt hydraulic motors to drive wheels for construction equipment.

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!"

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

(OP)
Ok that's starting to make total sense now, except one piece.

Quote:

Inside this machined ring and riding on the central shaft goes a plain/roller/ball bearing, depending on your cost and load requirements.

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

there's a lot of ways to skin that cat:

-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

makerjack, I'm glad you've discovered thrust bearings because you will definitely need them. But I'm still afraid of another style of loading: moment load. That's what happens when the direction of your load and your support are not in line with each other, and it can lock up an otherwise good set of bearings in a heartbeat. Thrust bearings are good, but unless they are designed to, they cannot absorb moment loads. That means you will still require good radial bearings in between the thrust bearings. And the best arrangement is always the same - separation of support points. What that means is that you want to make the distance between each of your thrust bearings as large as possible so you can separate the upper and lower contact points of your radial bearings.

RE: Advice needed - ballbearing solution for rotating table

(OP)
You guys are amazing, really. I can't thank you enough.

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

Depending on the exact design, it might very well work as desired.

RE: Advice needed - ballbearing solution for rotating table

Hub unit bearings from a Camaro are good for about close to one g lateral on a 3000 lb car with 26" diameter tires. I'll let others do the math.

ps: Jimmie Johnson lets me drive his car if I sell his parts.

RE: Advice needed - ballbearing solution for rotating table

In support of your point BUGGAR, they are good for MUCH more than that. Think about how much moment load goes through a wheel bearing when, for example, a Camaro cornering at full speed brushes a curb, or hits a small bump in the road.

RE: Advice needed - ballbearing solution for rotating table

(OP)
That should be more than enough for my relatively weightless spinning table then!

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

Basically right. Find a friend at an auto supply store who will show you several in different sizes and get a hands-on feel for the things. For experimental purposes, I use free worn-outs (not legal for re-sale) from, of course, Jimmie Johnson Chevrolet. You may need an internal adapter to mount to the diameter of your trunk or this could be built into your longitudinal spacer.

RE: Advice needed - ballbearing solution for rotating table

Yes.

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

The idea of a post with a bunch of stacked bearings and bent rods seems to have closed your eyes to all other opportunities.

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

Mike H., I was thinking that putting races on the bottoms of the rings and having rollers at the tops of the arms would work out nicely as well, but they all produce a different visual appearance and offer differing resistance to wobble and moment related deflection. The original version seems wobbly though aesthetically pleasing.

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?"

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

(OP)
Yeah I did look at the option of using a lazy Susan bearing, I just hadn't been able to find easily available sizes at the diameter of the outer ring (around 1400mm).

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

Don't forget that your bearings will likely require some form of lubrication, and some arrangement of sealing to keep the lubricant in place.

RE: Advice needed - ballbearing solution for rotating table

Automotive hub bearings are permanently lubricated and sealed.

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

(OP)
You guys have been so helpful, thank you. Managed to find 3 working wheel hub assemblies at various mechanics here in Berlin (after much searching) and here is the super first round prototype of the assembly.

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

Nice! I never considered leaving on the disks for adding brakes. Modern hub unit bearings come with ABS sensors that can be hooked up to measure the speed if you need to.

RE: Advice needed - ballbearing solution for rotating table

(OP)
Yeah that's awesome. Might need to do so if I am struggling to tune up the stepper. You're a legend BUGGAR, the wheel hub suggestion was a life saver!!!!!

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

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