The last one is my work horse It is a double acting crosshead type engine of my own design it has a bore of 1.250 and a stroke of 1.750! I built it to run slow and strong ( the ports feeding the cylinder are only.097)It runs at about 500 RPM on 70lbs. of air pressure and it is hard to stall it by hand ! It is shown hooked to a 1/3 scale power hacksaw built from Ron Hofmann's casting's kit( I built this saw for Ron and am writing a review on the kit for him) this engine runs backward for the saw and is not reversible so I had to twist the belt 1/2 turn to get the saw to run right!