Beauty and the Beast requires a gate to “magically” open and close. This is the mechanism we used to achieve this effect. Compressed air extend the rod of the cylinder, and the attached chain causes the sprocket to turn a fixed distance (in this case, 90°). The pivot point of the gate is attached to the center of the sprocket, so that every time the cylinder extends and retracts, the gate opens and closes.
The structure of the gate was 1″ or 1″x2″ box tube steel, and the rods were 3/4″ conduit (to minimize weight).
The cast finials were tack welded to the conduit.
This drawing shows the different components of the mechanism: blue for the cylinder, green for the angle iron and chain, and red for the sprocket.
This drawing shows the placement of the mechanism in relation to the closed gate.
The scrolls on the finished gate were lauan cutouts. The gate opened offstage, or toward the camera.
A close-up on the mechanism hidden in the rocks at the base of the gate.