[TChad]

Nice.

[dr_lew]

Yes, very clever. The magnets are doing double duty as electrical contacts. The current flows through them and the included wire coil. This current doesn't affect the magnets directly, but they interact with the field produced by the current in the coil to propel the "train".

so, representing the magnetic polarity of the magnets on the end, and the coil in the center, it has to be

+- -......+ -+

to run to the left, or

-+ -......+ +-

to run to the right.

-+ -......+ -+ and +- -......+ +-

won't go anywhere. I'm out on a limb here! But that's got to be right.