-wall_width = 3;
-
-wheel_width = 9;
-wheel_radius = sqrt(2 * pow(qr_size / 2, 2)) + wall_width / 2;
-
-motor_shaft_radius = 3.7;
-motor_shaft_flat_width = 4.8;
-
-tread_radius = 4 / 2;
-
-module mounting_screw_flat(){
- circle(0.9);}
-
-module motor_shaft_flat(radius, flat_width){
- intersection(){