Description: A flywheel is mounted on a pointed shaft which is supported in a metal cup. The shaft is arranged so that the center of mass of the whole wheel is as nearly coincident with the point of the shaft as possible. Ideally the wheel will be in neutral equilibrium and will spin without precessing. If the wheel is spun with the stem of the shaft pressing against the wire spiral the stem will roll around the spiral.

The top is spun by means of a thread wrapped around the shaft. The wire spiral may be removed to demonstrate the top with no torque. The windup string or another object may then be held on the shaft.

Brief explanation: the top rolls along the wire. The resulting torque causes the top to push against the wire and so maintains the rolling.

The top is sold by Lee Valley Tools who provide a description in their catalogue: Maxwell's Top ( with thanks to Lee Valley Tools for permission to use this document).

Cautions:

Concepts demonstrated:

Setup Time: Short

Difficulty/Commitment: Straightforward

Visibility: Visible in 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".