Quote Originally Posted by bigsi View Post
Your pneumatics have to develop more force than the spring to be able to compress it - so there must be an argument for just using the pneumatics and not bothering with the spring!

Si
Thats right, agreed. The main argument for the spring rather than pneumatics is the simpicity of the air system required to close the spring when compared to the air system required as a flipper. For an effective flipper using LP pneumatics you would require a buffer tank, large bore fittings and qev etc, basically you need a system which is optimised for flow and that takes up space.

On the other hand, if you use a spring, you get instantaneous power without the related problems of flow etc on pneumatic systems. The pneumatics to close the spring will not be effected by port sizes and flow etc because it does not matter if it takes a couple of seconds to cock the spring.....I think a set up with springs takes up less space and can possibly be more powerful...that said, it is not straight forward to build as it's not something I've seen built, so there's not much help around or build projects from where to take ideas.
I have a CAD design of one, which I'd like to build at some point...but I need to find time for it!