Metronome using SimMechanics

Metronome

I started with the demo of a simple pendulum: mech_spen in MATLAB® and simply added joints and bodies as they exist for the pendulum stand. To get the sliding motion with friction I used a Prismatic joint and used the velocity to compute a force dampening the sliding motion. So my model does not explicitly model the rollers on which the pendulum stand rocks.
Now the problem is that the synchronization does not happen and I am not sure what goes into a metronome that synchronizes the pendulums. Any comments/suggestions are welcome.