Model Steam Engine 1
The McCabe Runner
I saw plans for this model steam engine on a college engineering programs web page, and decided I needed to try it. The page is at this link. McCabe Runner
I started by gathering the materials. Total cost of about $5.00
Knowing it would be the most challenging, I made the steam valve first. It was made from a large nail. Roughed to shape on a bench grinder, then chucked up in the drill press and filed close to size. From there I finished the shape and sizes with emery cloth. A 90 degree bend finished it.
Next I tackled the piston and connecting rod. The piston was made out of piece of 7/16" brass rod. I already had the block bored and ported at this point. I chucked the brass up in the drill press and roughed it close to size with a file. Then using emery cloth I finished the diameter to have .005" clearance in the reamed bore of the block. A .045" hole was drilled through for the wrist pin and the slot was cut using a Dremel too cutoff disk and a small flat file. The connecting rod was made out of a piece of 1/8" welding rod. Hammered flat on one end, then drilled .050" for .005" clearance on the wrist pin. The other end was bent around a 3/16 dowel.
The flywheels are made from two pieces of 2" cold roll steel bar stock, cut to 5/16 thick. The piston side is drilled for press fit on a 3/16" dowel pin. The rocker side is drilled for .003" clearance. It get a hole drilled from the OD to the bore, that is tapped for a set screw. That will allow it to be rotated on the shaft to fine tune the timing.
The rocker was made from 1/16" thick sheet steel, drilled for clearance on the pivot pin, valve and rocker connecting rod. The pivot pin was made from a 1/4-20 bolt. The hex head was cut off, and the end ground, filed and polished to the sizes on the print.
This bearing support was made out of 1/16" sheet steel to hold the shaft. It was not stable enough, so I ended up making a new support out of a block of aluminum.
With the base drilled and tapped to accept all the parts, it went together easily. The rocker side connecting rod couldn't be made until this point, because the length of the rod would be adjusted as needed. A 1/8" pipe coupler was attached to the air inlet side with a heavy fillet of JB Weld for an air supply line to thread into to. I'll use a high pressure grease gun hose adapted to fit a pressure regulator, and a portable air tank for my air supply.
There were a few issues with the timing that had to be worked out. After replacing the bearing support with the aluminum block that became a little simpler. Ready to see if I can make it run.
With it set up to run on my very understanding wife's dining room table. I was ready to try it out. I quickly discovered that the air pressure is critical. A little low and you get nothing, a little high and the valve can't overcome the pressure to close off the flow on the exhaust stroke.
Finally got it all right, and it runs! I can throttle it a little bit by adjusting the air pressure slightly.
I have a feeling I'll be building more models...