Hello All: I just finished this little air engine this morning. It surprised me upon starting just as I hooked up the air line to it. I was prepared to adjust the valve timing and oil the linkages but it seemed to run very well.
I printed the plans off the web, [http://npmccabe.tripod.com/mccaberunner.htm] This site has several small projects to build and this is one of the students choices if I understand the write up. This was quite a uncomplicated engine to build and most things on it are not critical so it would be a good starter engine and possibly even easier than a wobbler, but still fun to build and add to my shelf.
A few liberties were taken in my version in that I added ball bearings on the shaft and did some soldering of rods into homemade clevis connectors. The valve is a piece of brass soldered onto the valve rod at the appropriate location for the stroke of the rod. The exhaust is directed out along the rod to the clevis on the rocker arm. It runs on quite low pressure, in the video it is running on a 40psi supply with the control valve closed but leaks some (which is why I could scavenge it out of the dumpster).
I'm happy with it-----don