Servo Horn Scotch Crank
This is the crank for the 'SG90 Scotch-Yoke Flapping Wing Rig' kit. It's a 36 x 16 x 6 mm stadium bar with a sunken seat on the back for a single-arm SG90 horn: a 7.5 mm channel plus a 10 mm centre recess. A 6 mm centre hole gives screwdriver access to the horn screw. At the other end, 12 mm from the axis, a 9 mm boss carries a 624 bearing (4 x 13 x 5) on an M4x20 bolt, which sits in a 4.5 mm clearance bore with a captive M4 nut pocket on the back.
mechanism kit sg90 scotch-yoke