Modeler’s Corner

By Staff
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Robert Best’s 1/3-scale Mogul 1 HP.
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Best drew basic plans for his model and cast the pieces himself from wooden patterns.
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Best crafted these scale-model igniters but ended up using a spark plug to run the engine.
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An overhead view of Robert Best’s 1/3-scale Mogul 1 HP.

1/3-scale Mogul 1 HP

I have two Mogul 1 HP engines on the original trucks.I am very
impressed with Moguls in general, which is why I decided to make a
1/3-scale model.

I drew basic plans, and from those and the full-sized engine, I
started to work.Because of the unusual shape of the engine, I
decided to make wooden patterns and cast them.

I have a small foundry and can cast aluminum very well.Brass is
no problem to cast, either; it just takes more heat and is more
expensive.The cylinder needed to be cored and I needed the full
benefit of water completely surrounding the cylinder.I also needed
a solid area for the igniter that comes on the side.

I made the core pattern and cast it out of Plaster of Paris. I
use the old method of making cores from fine sand and river sand,
mixed with linseed oil, then baking them for one hour at 400
degrees. For the molding sand I used Petro Bond; it is an oil sand
that I have had real good luck with. It is ideal for the home

Because of the way the crankcase is made, it required two
patterns and two core boxes to make into one piece.I decided to
make it in two halves and weld it later. Aluminum welds very well
with a TIG welder and it lets me do some machine work before
putting it together, such as locating the crankshaft in relation to
the cam gear. The crankshaft journals were line bored for bushings
after they were assembled.

The head was cast and iron valve seats were installed along with
steel valve guides.A cast iron cylinder was pressed with a
1-1/8-by-1-inch bore and stroke.

Moguls are throttle-governed engines so in place of a butterfly
in the head, I used a cylinder. This method is often used on small
model aircraft engines and involves taking a piece of bar stock and
milling a flat area that fits into the throat of the carburetor or
fuel mixer. This turns like a flat piece would in large engines or
small modern engines to regulate the amount of intake air.

The flywheels were cast in brass and all the fuel parts were
milled or fabricated from brass.The trucks are scaled down from the
original full-size trucks and I cast the wheels to match. I cast
enough parts for two engines and some spare parts for mistakes, as
there were plenty of them.

I worked on parts for both engines, machining where needed and
fabricating parts.As I started assembling, I found where my
mistakes were.The problem was for every mistake I had made, I
duplicated it by making two engines. At this point, I decided to
concentrate on one engine. If I was going to have to recast
anything, I wanted to do it before winter set in and it was already
October. Most of my casting work is done outside, and Missouri
winters are cold.

I got one engine assembled and ready for testing.I used a spark
plug and a buzz coil to run it the first time and it ran well.

I had made two igniters like the full-size engine, so I
installed one on this engine but I could not get it to run. In the
test, the igniter looked good.It was scaled down from the 1 HP
andthere is not a whole lot of room for it to operate. I am not new
to small igniters. I used them in 1/4- and 1/3-scale John Deeres
that I made in the past and they worked very well.I installed a
spark plug and ran the engine.I still hope to make the igniter
work, but the engine runs very well on the spark plug.

I can’t say this was an easy engine to make because of all the
small parts that have to be fabricated. But, when you are all done
and look back you think, “Well, that wasn’t so bad.”

Contact Robert Best at: 3521 N.W. 60th Terrace, Kansas City, MO

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