Automatic Chicken Coop Door - The Poultry Butler
mechanical_clutch

A unique mechanical clutch connects the door to the worm drive. The clutch holds the door securely to the worm gear resisting the prying action of a determined predator. However, if an obstruction prevents the door from closing the clutch will slip preventing damage to the motor and circuitry. Clutch tension is adjustable and the only maintenance required is periodic lubrication.