These steam engine plans are used in our "Mechanical Prototyping/Manufacturing" course......part of our Mechanical Engineering Technology AAS degree program at County College of Morris (Randolph,NJ)
The plans are heavily modified from a "Popular Mechanics" article written in the 1940's.....feel free to copy them to a disk (right click anywhere on the image)......we have no copywrite, so feel free to distibute them (just give us credit, as appropriate). My students call this engine "McCabe's Runner"...we've built dozens of them. At 30 psi air pressure(our standard test) we get about 2000 rpm, as measured by our timing strobe. A young lady with no experience built one in three classes that went 3000 RPM! An experienced (but overconfident) tool and die worker in my night class took six weeks to build one and it never got past 1000 RPM. There's a lesson there somewhere.....enjoy!
Construction Notes: (1)be sure that the cranks are 90 degrees "out of phase"...to understand this, bicycle cranks are 180 degrees "out of phase" (2)make the valve rod last....at correct length, the valve will be in "midstroke" when the piston is at top dead center (3)the rocker arm holes should all be ~.125 to ~.160 Not the .250 size shown on the print