Equipment: Maxwell's top.

What it does: The top will roll around the spiral. This is because the resulting torque causes the top to push against the wire and so maintain the rolling. The top is composed of a flywheel mounted on a pointed shaft. The shaft is arranged so that the center of mass of the whole top is as nearly coincident with the point of the shaft as possible. If the top is spun with the stem of the shaft free, the top will be in neutral equilibrium and will spin without precessing. If the top is spun with the stem of the shaft in the wire spiral the stem will roll around the spiral.

Concepts Demonstrated: Forced precession.

Classroom assembly:

1. Place the top in the stand so that the point of the shaft is in the metal cup and the stem of the shaft is in the spiral.
2. Thread the string through the hole in the shaft and wind it around the shaft.
3. While holding the base, quickly pull the string free. The top will spin and roll around the spiral.

Cautions: None.

Setup Time: Short.

Difficulty: Straightforward.

Visibility: Medium. This demonstration is appropriate for small classrooms.

Related demonstrations:

References: PIRA 1Q50.90
Sutton M-191; DHP Mu-13
Laithwaite mentions the top on page 59 of "The Engineer Through the Looking Glass". He describes the top as "a nineteenth century toy that has been almost completely forgotten", but does not call it a "Maxwell's top".

Original Construction: Purchased from Lee Valley Tools.