EMPLOYEE WAS HELPING EMPLOYEE TURN THE GEAR BOX IN ORDER TO LINE BOLT HOLES IN THE DRIVE GOG AND BUSHING. EMPLOYEE WAS SQUATTED ON HIS LEFT KNEE WITH HIS RIGHT KNEE JUST UNDER THE MOTOR BASE. HIS RIGHT FOOT BEHIND HIM. WHEN THE BELT ROLLED IT TRAPPED HIS RIGHT LEG UNDER MOTOR BASE. WAS RAINING.