Modeler’s Corner

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Tom Jamboretz’s model hit-and-miss engine.

Bar and flat stock hit-and-miss

I have been collecting old engines for about six years and am a
member of the Illinois-Missouri Tractor and Engine Club in the St.
Louis area. The more gas engine shows I attended, the more I knew I
wanted to make a model hit-and-miss engine. Most of the choices I
found were casting kits made by many different people from all over
the United States and the United Kingdom.

I finally ran across a hit-and-miss engine that was made using
bar and flat stock. It has a 1-1/8-by-1-1/2-inch bore and stroke
and no castings. This was a big advantage to me, as I did not have
a milling machine at the time. All I had was a small lathe and a
drill press. The engine was designed and drawn by Harold Depenbusch
in Kansas, and came with instructions, drawings and a parts list.
There were a few parts I purchased, such as gears and a miniature
spark plug.

I started with the base, which is made from 3/16-inch sheet
plate and heli-arc welded together. To this I added the iron
cylinder and surrounding water hopper. These I tack-welded and
sealed with JB Weld for a watertight hopper.

The head is made of aluminum with the 7/16-inch valves of
stainless steel. The valve seats are actually cut in the aluminum
head with mild steel guides and then lapped to give a good seal.
The piston and rod are also aluminum with two cast iron rings from
Otto Engine Works.

The biggest challenge to me, the non-machinist, was the
one-piece crankshaft. It is made from a piece of
5/8-by-2-3/8-by-8-5/16-inch flat cold-rolled steel. After laying
out the centers and sawing away excess metal, it went onto the
lathe to machine the throw. I had to make a long reach cut-off-type
tool to reach the throw. It worked surprisingly well.

After making the rest of the parts and reassembling, I had a
hard time getting the model to run the way I wanted. However, it
came around after a long thought process and help from a friend in
Oregon. It turned out the exhaust camshaft was made wrong, so I
needed to cut a new one to bring the exhaust valve timing to the
correct position. I did deviate from the plans on occasion, such as
changing it to run on propane (which required a demand regulator to
be made) and putting the ignition point on the other side of the
engine.

I painted it a very bright yellow and made the base from a piece
of white oak to give it some weight. I am very pleased with the
results and take it to shows where other engine enthusiasts can see
it running, hitting and missing.

Plans are available from Harold Depenbusch at (620)
429-2093.

Contact Tom Jamboretz at: 416 Larkhill Court, Webster Groves, MO
63119; (314) 962-3493; tpj1939@yahoo.com

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