Early in the design iterations for the Balcones 60 MJ power supply different options were considered, from a single machine to modular homopolar generators (HPGs).[1] A multiple machine option was chosen to provide greater system flexibility. Envisioned uses for the power supply were to weld up to 100 in.2 of metal, heat a 100 lb steel billet to forging temperature in 2 to 4 s, and conduct high level electromagnetic gun experiments.[2] A study involving detailed computer optimization compared drum type HPGs to disk type machines. For fixed location (such as large proof of principle laboratory experiments) the higher energy transfer efficiency and lower cost perjoule delivered made the drum configuration more attractive. The compact disk design was better for mobile applications where minimum mass is the primary consideration.[3] The six drum HPGs installed in the underground hexagonal pit in the Balcones lab are shown in figure 1.