Gravitrax Ferris Wheel

Laying out a continuous run of more than a dozen or so marbles requires they be continuously lifted to a high starting position. One option is to construct a ferris wheel. (Another option, shown on a another page, is a Gravitrax Archimedes Screw.)

I settled on four arms, each with a magnet, and put some Lego Mindstorms to work.

Ferris structure

Rotation is courtesy of a Mindstorms motor with a small pinion, driving the large gear wheel of the ferris structure. The resulting gearing allows the motor to run at 100% power.

Mindstorms motor and gearing

Considerable iteration was needed to arrive at a feeder plate that allowed a reliable pick-up by the passing magnet, and a stripper plate that prised the marble away from the magnet for delivery.

Feeder plate (Feeder.STL)

The feeder plate has a half-unit (5 mm) slope, a small well for the marble, a sloped exit ramp, and a shroud cover for the next marble in line. I found that it was often possible for the passing magnet to pick up two marbles at once.

Stripper plate (Ferris catcher.STL)

It soon became obvious that the stripper plate needed to rest on more than one pillar or tower to reliably and securely strip the unwilling marble from the unwilling magnet, particularly if the ferris was driven at 100% power. And after a little more trial and error, the pate on either side of the stripper was designed to take a couple of marbles as ballast, or another Gravitrax plate to hold half a dozen or more marbles.