The worm

It passed through my mind that the valve mechanism could be designed so that the manifold pressure will not be able to put it in motion "on a whim." It is desirable for the mechanism to be able to resist any reaction applied by the valve pressure. So long as the mechanism is at its endmost position, the motor power supply might be switched off. This is why I opted for the classic worm gear. Pros: The mechanism is irreversible (see above). High gear ratio, hence, high torque at the output shaft (at expense of the revolutions). The mechanism works silently. Cons: The efficiency coefficient is low. The friction resistance is high, hence, the gears emit heat and require lubricating. The gears get to wear out fast. IDE: Autodesk Inventor v.2020