360 Newton's Cradle

In short - a Newton's cradle where the ejected element swings around over the top to strike the first element. Ie if you number the elements from left to right 1234, when 4 strikes 3, 1 is ejected, swings over the top and strikes 4, ejecting 2, etc etc ad nauseum.

I've looked but not found an example of this.

Requires a lateral axle (so they are all concentric about a common axle) rather than a longitudinal one, and therefore the elements won't lie naturally in a straight line but will follow the curve of their radii. It will be interesting to see how good the force transfer is along a curved path between the elements rather than a straight one like most NC's.

The yoke for each element would be a two cords forming a Vee, and you simply have successive elements having a more acute Vee so that the cords do not interfere with each other.

Starting this thing could be a bugger, but that'd be half the fun. Also thinking that because the elements will at rest sit in a shallow arc at the bottom, if they're spheres they might slide past each other. So maybe they're better off as short rods with slightly chamfered ends rather than spheres.

Executive upgrade - use a small linear accelerator somewhere along the arc of travel to add a small impulse that's callibrated to exactly counteract the frictional losses. This thinng will have to operate fairly energetically as each element needs sufficient velocity to smoothly travel over the top without slackening it's yoke - and so your air friction losses will be relatively high. Another option is to have rigid yokes on bearings so that you only need just enough velocity to "go over the top" which, when I think about it, would have a cool speed up-slow down effect that would look much cooler than the original concept.