Pimoroni micro metal gearmotors with extended back shaft pimoroni com0800 this 501 ratio micro metal gearmotor from pimoroni can achieve up to 420rpm and its small size makes it ideal for small robot platforms or other light mechanical loads it has a 3mm diameter d shaped output shaft which is 9mm long and a 1mm diameter back shaft which is 45mm long the back shaft is a great spot to install an encoder to track the motors speed and position it is part of a range of motors that are all t