| This Inertia Apparatus is at Kenyon College. I have been looking
at it since 1964, have often wanted to include it in an experiment, but
have never found the right place.
An improved version of the apparatus is shown in the ca. 1930 catalogue of Improved Physical Apparatus for Advanced Laboratory Work of the Gaertner Scientific Corporation of Chicago, a firm dating back to 1896.
A mass fastened to one end of a thin string wrapped around the rim of the disk gives the rotating system an angular acceleration. A disk of specially-prepared paper is attached to the face of the disk, and a stylus on the end of the vibrating tuning fork traces a sinuous line on the paper. The rack and pinion arrangement at the base of the tuning fork allows the radius of the track to be changed for subsequent runs
The sinusoidal track acts as a timing device, and makes it possible to obtain a record of angular position as a function of time, from which the angular acceleration can be obtained. This can be obtained from the angular acceleration obtained from the applied torque and the value of the moment of inertia of the system supplied by the manufacturer.