I recently "re-found" this engine after something like ten years. It has no bearings, the piston is iron, the cylinder and boiler are ordinary plumbing copper tube, the valve assembly is made of three pieces of brass. The flywheel is made of steel pipe filled solid with.. lead! I don't think you'd see that kind of thing today in shop class. :)
So I just had to make it rotate things like different fans and, finally, an old hard disk motor. Surprise! I got enough voltage to illuminate some LED's. Alternating current. Puts quite a strain on the machine to produce some 2-3 volts...
Seeing this engine rev up I can only wonder how fast it would go if it just had three tight-fitting bearings.. Now there's awfully lot of clickety-clak and vibration.
My next engine will have a somewhat larger and slower piston, as it will have this piece of solid iron for a flywheel. This beauty along with the sturdy aluminum frame was ripped off from an ancient 9-track recorder I found in the dumpster. Notice the solenoid-operated clutch, it will make the rubber wheel on the left press hard on the main axle. Will make for some nice robotics (connecting / disconnecting rubber bands).