Maxwell’s Dynamical Top

In early 1856, while still at Trinity College, Cambridge, James Clerk Maxwell described a “great top” to his father that later became his Dynamical Top, both of which are pictured below.

The wooden version, without adjustments, was demonstrated to the British Association in Cheltenham, England in 1856. The version made of steel and brass was made by Charles Ramage of Aberdeen, Scotland, and demonstrated to the Royal Society of Edinburgh in 1857.

topsm

This version of the Dynamical Top was made by Harvey and Peak, instrument makers of Beak Street, London in 1885. It includes all the most important features of Maxwell’s Dynamical Top.

It must be remembered that at the time – the mid 19th Century – there was only a rudimentary understanding of the earth’s rotation in space, as well as space itself. The Top was used by Maxwell to demonstrate not only the motion of the body around its axis of rotation, but also the motion of the axis of rotation itself. The top can be adjusted to demonstrate steady spinning, precession and nutation. The colored disc is used primarily to demonstrate nutation, however like the phenomenon top spinners call “warping” it is easy to observe precession also.
The center of mass of the top can be adjusted up and down relative to the contact point using the weight under the colored disc. The nine brass screws can be used to adjust the motion of the disc on the axis to produce varying nutation and precession traces as we as to balance the top. While Iocopo Simonelli normally balances his spinning tops by adding weights, in his Top #23 he used three screws in the rotor to adjust the balance, in the style of Maxwell’s Dynamical Top.

iacopo simonelli #23

The most interesting aspect of the Dynamical Top for me is that Maxwell designed it primarily to demonstrate its motion when NOT perfectly balanced and spinning on an axis over the center of mass, which is the motion top collectors admire most in a spinning top!

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