Spring engines and the release of the cords at point a
Drum-and-arm throwing machines with a note on safe release
Several ink studies set out spring or torsion engines built around large drums and sprung, curved arms mounted on inclined timber frames. A block of mirror-script beside the drawings, keyed to a point a, states that the cords at a must all be taken away before the instrument lets go of its forces. The sheet works through how such an engine is charged and then safely discharged.
On this page
Clear the cords at point a before release
The note keyed to the letter a explains that the cords gathered at that point must all be removed before the engine releases its stored force. It reads as a caution about the order of arming and firing the spring device.
Drum-and-arm spring engines
The studies combine a large cylindrical drum with a sprung, curved arm, each carried on an inclined timber frame. Cords and pivots link the drum to the arm so that turning the drum charges the mechanism.