This is the electric motor that replaced the original overhead belt-driven drive on the mirror-grinding machine built by George Willis Ritchey at the Yerkes Observatory in Williams Bay, Wisconsin, in the late 1890s. The object is a commercial product, a Dynamatic "Ajusto-Speed" 5 hp 1750 rpm electric motor, model MO 100005-0904, serial 72450-4, with Cleveland right-angle drive. The original grinding machine was used under the sponsorship of Hale to grind a 60-inch mirror initially intended for the Yerkes Observatory. The grinding machine was moved to Pasadena in 1904 to complete work on the mirror; at some point it was transferred to the California Institute of Technology. The Institute then sold the machine to the Lick Observatory of the University of California in 1949. The machine was used for making numerous mirrors over the next four decades and extensively modified over that period. It is not known when the replacement motor was installed, but it was likely when the machine was transferred to the Caltech campus. It was donated to NASM by the Lick Observatory in 1993 and shipped in March of that year.
Gift of the Lick Observatory, University of California.