The Marathon motor used on the Taig lathe is a poor choice for variable speed, even on a variable frequency power supply.? It has a start winding, controlled by a centrifugal switch that will turn on if the motor slows down too much.? This winding is not designed for continuous operation, and will soon overheat.? This motor is designed to operate at a fixed speed, determined by the power frequency.? I rigged up my Taig lathe with a heavier version of the 24 volt scooter motor and pulse width modulated? control used by several people on Unimats.? My motor is a 1/3 hp Dayton 24 volt from an estate sale, connected to a heavy power supply and the usual pwm controller.? The Dayton motor is more powerful than I need for the Taig, but is far smaller and lighter than the original Marathon. It turns up to 4000 rpm, so I only need the slowest 3 speeds on the drive pulley. ? I think a permanent magnet field DC motor and PWM controller will give you the most bang for the buck.? There are several past threads on these conversions for the Unimat, some giving sources for the parts required and the procedures for the conversion.?
Chuck Daldry
