The accompanying illustration, Fig. 173, shows how a good-sized gyroscope can be made out of an old bicycle. The turntable A is furnished with a ball-bearing mounting by attaching it to bicycle pedal. The pedal is secured on a stand, to which the pedal spindle is bolted. An ordinary bicycle wheel is indicated at B with its axis extended, by screwing on a pipe in place of the ordinary nuts. At one end of the axis is a hook, C, by which the wheel may be hung and he swung as a pendulum to show the curious path taken when the wheel is spinning horizontally, and also how it resists any change to its plane of rotation. D D are supports with grooves in which the extended axis can rest. Stops E E E are to prevent the wheel from sliding down the groove when its axis is raised toward the vertical. The apparatus is worked as follows:

Fig. 173 - Bicycle wheel gyroscope.

First. Placing the wheel B in between the supports D D, the turntable can he spun round, to show that the wheel remains inert when not spinning; spin the wheel (which can be done by the hand quite fast enough), and on revolving the turntable the wheel rises toward the vertical, as shown in sketch, supporting itself. Reverse the direction of the turntable, and the opposite end rises with similar results.

Second. Remove the wheel from the turntable, and place the axis on one of the supports D D, so that it comes between the stops E E. The other end is held in the hand until the wheel is spun, when it will revolve in the usual manner of gyroscopes, carrying the turntable with it.