Stubborn, Stupid, or just Plain Crazy?

I was determined to use parts I already have, rather than buying new parts. The wheels I had were the correct diameter for the model I’m building, but four of them were too thin, none of them had cast in counterweights and the stroke was too short.

Previous articles in this blog deal with adding material to make the wheels thicker and making counterweights out of aluminum and epoxy. The remaining problem was the short crank length. I’m building a freight engine, not a race car. The stroke on the original Little Engines 4-4-0 was two inches. I needed a stroke of four inches to go with my two inch cylinder diameter.

I started by plugging the hole for the crank pin on the original wheels by pressing in a steel pin. I epoxied a triangular shaped piece of steel between the spokes where the new crank pin would be located.

I made long oval plates from 1-1/2″ x 1/4″ cold rolled steel. The ends were rounded on the mill using a rotary table.

The plates were epoxied and screwed to the wheel. The wheels were mounted on the face plate, on the lathe. I took a light skim cut to ensure the plates were parallel to the back of the wheel and six wheels were close to the same thickness. The two blind main drivers were made 1/8″ thicker to match the thickness of the thicker counterweights. I made a fixture to drill and mill the new crank pin hole in the same location on each wheel. I had to ream the holes in my drill press because I do not have enough travel in the “Y” axis on my horizontal milling machine.

The last operation was milling a one inch diameter counter-bore on the back of each wheel at the crank pin location. The crank pins will be pressed in, but part of the press surface will be epoxy, so I will screw the pins in from the back with a large washer for added strength.