Hand-cranked shell game

[Jon]

GIF and short video of a hand-cranked shell game from Per Helldorff.


https://s3-us-west-1.amazonaws.com/h...shell_game.gif

[Jon]

I still haven't figured this one out. Clever use of moving magnets?

[mklotz]

Suppose EACH cup contains a ferrous ball held to the inside top of the cup by a weak magnet. By moving a stronger magnet concealed beneath the table under a given cup, the ball in that cup is pulled from its restraining magnet and held to the table when the hands are lifted. When the hands come down, the under-table magnet moves away and the ball is sucked back up into its cup.

The rotating circular platter has pins placed at different radii. I think they are the ones locating the under-table magnet.

Just a guess, but that's how I would think about designing it.

[PJs]

Good catch Marv, Thanks! I was wondering my self how the magnet in the hands might work but did notice the little flags on the horizontal disc seemed to be doing something else.

[mklotz]

You can see the flags pressing on a small, movable wooden bar that's under the table.

I based my analysis on the fact that the spherical ball does not roll when it's revealed. Given the vibration induced by the hand-cranked motion, some force must be restraining it; the logical candidate is magnetism.

The gray skirt on the table is not just decorative; it's there to hide your view of what's going on underneath.

[PJs]

You are the Man Marv...and your observation just made me figure out why the pegs are in an elliptical pattern to vary the motion on the lever to move the magnet in a linear motion for each hand. Still can't figure out what that inboard one is for though! This is a good test of critical thinking, imho.