Above: right side view
Below: left side view



Cylinders: 2
Type: 45º V-Twin, DOHC
Bore: 1.062”
Stroke: 1.125”
Displacement: .995 cu in/cyl x 2 + 1.993 cu in
Compression Ratio: 7.9:1
Ignition: Glow plug
Cooling: Air
Fuel: 15% nitromethane/methanol mix
Max. RPM: 11,000
Est: Horsepower: 2.0


Background -- This engine was a somewhat similar version of the first DOHC Harley-Davidson motorcycle engine (the one prior to the current Porsche-designed model). It doesn't follow the Harley pattern exactly but at least looks somewhat similar.

Construction -- The valve train was timing gears and timing belt to the cams. It was a somewhat difficult engine to make and the results were OK but not stupendous. It could use more development. Of course you can say that about almost any one-off engine. The second one you would make would have some improvements. This engine crankcase was made in two halves which I made in pieces which I were welded in place. I then finished them in the mill. The crankshaft was steel and a bear to make as it was in three pieces per the Harley system. This consists of crank throws with tapers to lock into the main journals. I'm not sure that Harley did this in this engine as I never got to see the inside of one, but it requires some very close tolerances.

Operation -- This twin ran OK but used a single model carburetor which was not too flexible. If I do any more  develpment on this engine I would design and install a couple of slide valve carbs.

On Castings...

I got interested in making my own foundry and casting some of the parts for my engines. It sounded good but I soon realized tha if I were to only make one unit I might as well go directly to the billet and hog the parts out from scratch. After all, with castings you have to make patterns, get them to cast properly, and still machine them. I finally decided to eliminate the casting process, since I only make one of each engine. The foundry worked well but was not much of a solution to making small engines, one at a time. I spent time later in making fixtures which gave me two more axes in my mill. I call it MDC or "manual digital control".


Detail of carburetor and camshaft drivetrain.

(click on buttons)



All contents © copyright 2013 by E. F. Ellison. All rights reserved.