First off, check the counterweights – if they're off you’ll get wobble, not rhythm. Use low‑friction bearings and keep gear teeth smooth; rough teeth bite and ruin timing. Test at a slow speed before you crank it up. Make the frame rigid – don’t let the joints flex. Match the motor torque to the load, and if you feel vibration, look for resonance – add a bit of damping or shift the mass a little. Simple fixes, no fuss.

Sounds solid. Keep an eye on the alignment—if anything’s off even a millimeter, the whole thing can go off‑beat. When you hit that lower rpm, let it settle, then bump it up. You’ll see if the pad does the trick or if you need more mass. Good luck, and keep that rhythm tight.