There are four sprockets that tie everything together: one is connected to the end of the motor, which is then chained to a second sprocket on a rotating idler shaft containing a third sprocket, which is then chained to the fourth sprocket on the axle. The sprockets are bored to accept different shaft sizes, and to make up the difference the plans called for K&S brass tubing in telescoping sizes that increase in diameter as necessary Then, the set screws on the sprockets are tightened and compress the tubing together which retains the sprocket. I didn't believe it would work but it did. However, if those joints eventually fail I may just turn a shaft to the proper diameters and skip the tubing bushings altogether.
The motor is an oscillating cylinder that came with the boiler kit. It has connections for the steam lines in and out, a flywheel on the back (or front, depending on perspective), and a spring to adjust the amount of pressure the cylinder has on the port block. It all came pre-assembled but the screw might need adjustment after testing. The last sprocket attaches to the end of the shaft that also has the flywheel and a chain connects it to a sprocket on the idler shaft. I made sure everything was in perfect alignment, marked the four mounting holes on the floor deck, and then drilled them out. The motor was then screwed down.
The engine utilizes a simple displacement lubricator which is available from Roundhouse Engineering, one of the oldest Gauge 1 live steam companies still in existence. Their locomotives are simple and despite having multiple models all share a family appearance, but they are also bulletproof. I started another scratchbuilt locomotive years ago based on their parts and may someday get back to it. Anyway, a displacement lubricator works by allowing steam into the body of it from one side, the steam converts to water and sinks to the bottom of the body, and oil gets displaced up and out the other side. Simple, but it works.
Finally, once completely cooled I washed it with alcohol to remove all traces of the flux. Then, I laid it out on the deck and drilled holes for the mounting screws. Too close to the edge of the deck and it might break off, but too far inboard and it could interfere with the boiler. Now that I look at these pictures, I wonder if I should have used hex bolts and nuts instead of Philips head screws. They can always be changed later if I want. I still need to connect everything up with silicone tubing but I have that on hand and it shouldn't be too difficult. I am now contemplating whether I want to paint all this stuff or leave it unfinished brass. I am leaning towards not doing anything to it.