Modeler’s Corner

| October 2007

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 foundry.

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.