ST wrote: snip ..
3. The original design is started by gravity alone. The motion wheel, because it IS balanced, must be given an initial push.
4. I have designs with and without springs...they all work.
Yes, because it is balanced it must get a push start - it is how you do that which is important. It should imitate real world as far as possible.
Other elements can act like springs also because sometimes they have elasticity quotients to deal with. Try replacing them with generic cord-to-cord and look in >Properties. A dampener is usually required.
Usually I use either a weight pinned to it to induce torque which then falls off - using say a rod connection - in Properties>Active When uncheck this box and put in an equation t<0.5 which means time is less than 0.5 seconds. It will disengage after half second and fall away.
Or I add a force vector element (constraint) and do the same with the Active When box.
I think the point is in the Energy Budget scenario.
If it is balanced and stationary, and you have accounted for any and all PE's, then that is the start condition. Add to that the RKE/momentum, whatever given and it should at best maintain that oscillation speed.
IF it accelerates then things get more interesting - because if it accelerates it has more RKE of KE Translational or whatever - if this is GREATER than the ACTIVATION Energy given it to start movement then it is officially a weird result *grin*.
Good luck, look like such a simple concept needs a quick real world build if it passes muster with the usual sim idiosyncrasies covered.