Hi! I built this circuit according to your circuit diagram. The halls sensor detects the magnet and generates a pulse which is present in Pin 1 of the CD4001. But there is no pulse coming out from pin 3 of the CD4001 and so the rest of the circuit beyond this point is not working. I already double checked all the physical points of the circuit board to be sure it was not a mechanical failure.  Then I also tested your circuit diagram in a simulator and came up with the same non-functioning result. I cant understand why the project is not working here but it does work in your video. Can you offer me some advice please?

Excelente! I've been looking for an application like this for quite some time now. 

The strength of the "kick" can have a small effect on the timing. I once worked on a related projected where the object  kick came from discharging a capacitor that charged while the object was moving back and forth. For just the right size cap and time constant the whole thing acted as a form of negative feedback stabilizing the timing. You might want to give this a try for fun.

Very cool, I love it that you did this with an analog circuit. Nice work!

thanks for your comment !

A magnetic pendulum is something I have high on my wishing list to build a more precise version of a Bulle-Clock. Do you plan to include a potentiometer to vary the time of the magnet for better control of the timing?

Hi ! The frequency or period of the pendulum is determined mainly by the length of the rod/chain and the gravitational force. The electromagnet has a minor effect on the period. Regards!