Speed control of spring motor
Orange leaf springs tend to get their neutral position and push violet flange to the left. Centrifugal forces of pink weights tend to move the violet flange to the right when the speed increases and cause the friction at the contact place between brown pad and violet flange. Grey coil spring tends to free accumulated elastic energy and to make the blue output shaft rotate very fast. The said friction reduces speed of the output shaft. Red screw sets position of the pad. Move pad to the right to increase the output speed. This mechanism is used in gramophones. It is possible to replace the gear drive by a worm drive of large lead angle.