An elementary treatment of the theory of spinning tops and gyroscopic motion, by Harold Crabtree.

8

INTRODUCTORY CHAPTER

The "Spider tops," which are frequently sold in the streets
of London, consist of a heavy little disc mounted on a spindle
(Fig. xIv.). When the disc has been set spinning a small curved
piece of metal is placed to touch the toe, and at once begins
to slide round it, first the side (a) in
the figure, and then the side (b), the
motion continuing backwards and forwards till the top comes to rest. The
fact is that the toe is magnetic, and
this being the case it is easy to see
that the rolling of the toe on the side
of the metal produces the motion.
But Figs. xv. (a) and (b) illustrate a
_-_a- top, whose spindle behaves in exactly
b ^_^^the same manner as the toe of the
FIG. xIv. spider top, and yet is in no way?magnetic. The action is purely mechanical,
as we shall explain in later pages. It is an attractive top
to watch, especially as it rushes round the corner when it
comes to the end of the coil.'
FIG. XV. (a). FIG. V. (b).
But the most interesting top of all is undoubtedly the
ordinary gyroscope. That depicted in Figs. xvI. to xxI.,
although merely sold as a toy, is nevertheless capable of
illustrating the gyroscopic phenomena which have been so much
made use of in modern mechanical invention. If the gyroscope
is spun as in Fig. xvII. the surface on which it is standing
should be as smooth as possible. See page 49, question 14.
*This top, which is known as a "Gyroscopic Top," can be purchased of
Newton & Co., Scientific Instrument Makers, 3 Fleet Street, London, E.C.,
price, ~1. 6s.