I´ve modelled a new spiral with less slope and only one track because this worked better in my case. The spiral is modelled for 12mm marbles (i.e stainless steel balls from car ball bearing).

In my case I´ve used the ccw version with some slight modifications at the machine itself and it worked perfecly. However, the original marble machine may require the cw version, but I did not test the function of my model, which is just a mirrowed version of the ccw.

Great job of Tulio and many thanks to provide this machine