Planar-flow spin casting is a rapid solidification process used in the manufacture of thin, metallic ribbon, and foil. Liquid metal is solidified against a cool, rotating wheel which absorbs the super heat and latent heat of the metal. Industry typically implements an actively cooled wheel. However, validation of unsteady models requires observations from unsteady experiments. Experiments from our laboratory with an uncooled wheel show different temperature–time traces at different positions. Given a specified heat loading, a full conduction model predicts temperature fields within the wheel as they evolve with time. In this paper, we obtain reduced-order conduction models which take account of the various relevant length- and time-scales, with guidelines as to their validity. Model validation compares against measured temperatures from our casting machine. Finally, the model is modified to include internal cooling of the wheel to predict steady state behaviors. Spin casting can freeze molten metal sufficiently rapidly to achieve metallic glasses for a number of alloys whose properties in that state enable ultra-efficient energy conversion devices, alloys of increasing importance to energy conservation/harvesting.