On his pages Earl Morse discusses the Colt disc axial engine and shows a newer prototype by Joe Ritter (steam happens #19). He provocatively suggest one might rework an automotive ac compressor as an engine. I've been putting some thought and research into this. (With all the stuff online its amazing how little information there is on how they actually work). Suffice to say, there are (at least) two distinct kinds of swashplate compressor, and its very difficult to work out which designs would be best to try to adapt. Adapting would mean using the pistons, swashplate, drive shaft and casing (and bearings etc), but building new valve systems - probably rotary plates like hydraulic motors, driven by the drive shaft... Before I bite the bullet and buy a couple to play with, I have a nagging worry that the swashplate mechanism, as implemented in automotive ac compressors, might not be reversible - In the sense that you can't drive the output shaft of a worm gear. Does anyone have any advice on types of ac compressors or reversibility? Or any other observations/opinions? Utube is full of two stroke IC 'conversions' etc. I don't want to pursue an adaptation that is more difficult and less useful than building one from scratch. thanks!