The figure demonstrates the vacuum clutch system. This kind of clutch utilizes the existing vacuum while in the motor manifold to work the clutch. The vacuum clutch is made of a reservoir, non-return valve, vacuum cylinder with piston, and solenoid valve.  The springs keep the flywheel going ahead or backward https://clutch-plate27021.verybigblog.com/32308249/details-fiction-and-clutch-plate