Spring engaged clutch and spring engaged brake designs are only indicated for applications requiring the clutch or brake to remain engaged when the air supply is removed or fails.  A fail safe holding brake would be one example.  Another example can be seen on our Applications page where a spring set brake was used on an Universal Studios attraction.   Additional links:  spring set flange mount brakes, spring set NEMA frame brakes, end of shaft mount spring set clutches - regular duty and heavy duty.  Air engaged clutches and brakes are more suitable for cycling applications.  If there is any question which is best for your application, contact Mach III’s engineering department for a quick answer.