I'm planning on building an inexpensive rotating lens speaker, similar to the units used with organs. The design calls for a rotating lens made of 1/4" plywood, about 12" diameter to be rotated at about 5 to maybe 20 rpm. Speed of response is not critical. It might be a nice feature to have it ramp up/down, so an auto mode might be nice also. What I must have though, is a cheap, durable motor and externally controllable speed control.