I've really tried to find something online that's suitable but what I'm after is

I've two concentric circular rings, one of which has a diameter about 10mm smaller than the larger .

The rings themselves are in the region of 300mm diameter.

I'm trying to find a way to connect the two together and allow the smaller to 'slide' in a circular rotational way within the larger one.

I'm also trying to let the 2 rings pivot vertically in relation to each other - the intention being of producing a gyroscopic-esque motion.

diagram of it

What type of bearings/tracks/spindles would suffice?

  • $\begingroup$ Can you add a diagram or picture of what you are describing? $\endgroup$
    – Ian
    Feb 18, 2014 at 15:32
  • $\begingroup$ thanks @Ian I've added one to the question - sorry for the simplicity :) $\endgroup$ Feb 20, 2014 at 16:23
  • $\begingroup$ What kind of load and rotation speed are you looking for? $\endgroup$
    – Mhz4.77
    Apr 4, 2014 at 1:43
  • $\begingroup$ The plan as you have drawn it is not so good. The bearing will have to slip on either the top or the bottom of the groove and it will have to be contained in a groove to prevent it moving from top to bottom in your first image. A Powerball uses the problem to advantage to add rotational torque to the spindle. en.wikipedia.org/wiki/Gyroscopic_exercise_tool $\endgroup$
    – KalleMP
    Apr 7, 2015 at 16:12

2 Answers 2


I think you might need two "lazy susans" in the channel. Shown in green in this image. And then the rider in the channel does not have to be round. In fact it is probably best to rigidly attach to one side of the lazy susan. Now you can put a simple shaft and bearing in the inside ring.

One more note, if the load is not great, and you don't care about cantilevering the lazy susan, you can get away with only one lazy susan on one side.

enter image description here


Been searching for the nearly exact same thing, probably have to build it myself...bearing-in-track was the only way to allow 3 concentric rings to rotate, spin, and tumble independently of each other. My design had a "track" for the bearing to travel in also but an additional track on the outside of the inner ring, with a bearing on either side of the spindle. Got me?

Have found nothing of the sort in 12 years of looking. Any help in this direction will get me exited all over.


  • $\begingroup$ How about two curved tracks with sprocket holes. Like a loose/worn bicycle chain curved on edge. One in the top and one in the bottom of the groove. Then three small sprockets to engage one in the top and two in the bottom to lock each pivot point in place. If you want to make it very complicated you could have synchronized drives (servo/flex shaft) to make sure the pivots are always opposite and use the same drive to move it about or servo assist free movement if you want to make a vomit exerciser. $\endgroup$
    – KalleMP
    Apr 7, 2015 at 16:19

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