It is required to center/align the motor shaft accurately to the gearbox Pilot Shaft.
A “pair of compasses” approach is implemented in order to draw a circle on the Adapter Plate.
The circle is exactly the same radius as the four bolt holes on the motor front face.
A Compass Arm is machined to fit tightly over the Pilot Shaft.
A suitable hole is cut approximately in the center of the Adapter Plate for the Compass Arm.
The positions of the mounting holes for the Adapter Plate is obtained with the aid of the original gearbox spacer plate, used as a stencil.
The four motor bolt holes are drilled in the Adapter Plate on the drawn circle.
The Adapter Plate is fitted to the Motor with four bolts.
The Motor is mounted on the gearbox with the aid of the Adapter Plate mounting holes.
See illustrations below.