The beating heart. The crankshaft is what will translate the power of the steam engine to the gears and wheels to make the locomotive move down the rails.

I began by machining 1/2″ steel blanks which would become the four counterweights.

The 1/2″ holes for the main shaft and crank throws were drilled and reamed.

Then the angles were milled. A 1/2″ pin registered the counterweights together as they were machined all at once. Flipping the group over yielded the same angle on the opposite side. The next step was broaching the keyways (unfortunately, I got got ahead of myself and didn’t take any photos of that process). In order to make the broaching job easier, I did however upgrade my manual 20-ton HF hydraulic press by replacing the original jack with an air-operated jack, which I did take photos of.

This is the new bottle jack installed with the air motor situated behind it.

I robbed the ram from the old bottle jack and welded it to the cross beam which gives me about 2-1/2″ adjustment on the parts to be pressed.

I also turned an aluminum knob and attached it to the pressure relief valve for quicker jack raising.

The finished mods in place. Now all I need to do is squeeze an in-line air valve lever to vary the speed of the press. It works great!

Next, I had to machine the final curved shape of each counterweight. On to the lathe…

I made a simple aluminum fixture to hold the counterweights in the 3-jaw chuck to turn the final shape.

Keyways then needed to be cut in the crank throws and main shafts next. Back over to the mill…

Using a #304 woodruff cutter I cut the key ways in the crank throws and main shafts.

For final assembly, I heated the counterweights to 400°F in my heat treat oven for about 30 minutes before installing the crank throws and main shafts which had been chilled with dry ice. The components were machined for a .001″ interference fit and went together quite easily with the temperature differentials.

While the crankshaft does spin in the bearings, it is TIGHT!! I’m going to have to do some minor lapping to break it in for sure.

The finished crankshaft, engine block, crosshead guides, and cylinders mocked up on the locomotive frame. It’s starting to really look like a shay now!