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Thursday, April 5, 2007

Simplex Build, Crankshaft

The crankshaft is made out of 3/16" drill rod, with a hole drilled into one end, and a few flats and another hole cross drilled in one of the flats so as to intersect with the end drilled hole. All these holes and flats act to form the valve gear that feeds steam to the cylinder and piston. That's the real beauty and the simplicity of the Simplex engine. The valve gear and crank are all one part.

What you see is two crankshafts built end to end on one piece of drill rod. That big steel slug in the middle is a problem solver. The construction notes said to mill the flat on one side of the crankshaft, rotate the shaft 180 degrees, and mill the other flat. My problem was how to rotate the shaft exactly 180 degrees, given the equipment I had on hand. I used the left over round from building the crank disk. I end drilled it with a 3/16" drill on the lathe, then milled four flats on it and installed a socket head screw in the middle of it. A set screw that fit flush with the surface would have been better, but I had a socket head screw. I used this to hold the drill rod for the crankshaft in the mill vise, milled and drilled the flats on one side, then rotated the whole thing and milled the flats on the other side. Problem solved. After that, I cut the two cranks apart, and faced them to length. I couldn't resist fitting things together at that point. All of these parts are starting to look like two engines.

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