The 1/8 brushless motor rules are being updated slightly to clarify some of the parameters that are already in existence. These rules don’t effectively change anything, they’re simply to better define motor construction requirements that are already in place to avoid leaving loopholes open that could disturb the market.
Maximum overall length is 77.00mm measured from the mounting face of the motor to the furthest most point of the end bell, not including solder tabs, lead wires, sensor plug and housing, or original manufacturer’s logo or name. Motor mounting holes must be on 1.00- inch (25.40mm) centers.
Motor stator maximum outside diameter is 39mm.
External shaft diameter shall be 5mm (.197 in.). It may only be either a 2 pole or a 4 pole design with a maximum 12-slot stator.