Hi guys. I need some ideas on making something similar to one of these: http://www.pumpschool.com/images/Cutaway-Classic+.jpg [Broken] Only the one I'm trying to make will pump 200+PSI, and be driven from red hot exhaust. Swept volume is going to be around 4 liters per revolution. I looked into buying one from the boys in china, but they're about 10k for that size, and not even equipped with cooling passages in them, which I obviously need to run it from exhaust gases. My idea I had was to create a 2D end aspect of the lobe rotor, and then use a plasma cutter to create many many pieces that would later be held together by long nasty bolts. Does anyone know how accurate a plasma cutter is for this type of thing? I'm thinking if this needs to be CNC'd from solid steel stock, It would probably cost 20k for the first one, and at least 5k each for more...... I could find roots blowers from old detroit diesel engines, but those were never designed for the pressure I plan to inflict.