Here you go red devil.
This is running on 120 PSI and it cost a small fortune (at least for this old man) to have it built from scratch. It could be much lighter and much more suitable for the application, and it is positive displacement.
That is the reality of innovation these days.
Like an alternator you control the engines speed by varying the load which increases or decreases the resistance to air flow.
Built and operational with video proof Dec 20, 2009.
regards
Mech