When I tested the dry fit of the first cylinder parts, I still needed to get the guides straight. Little did I realize at the time how difficult that would be. I was even more surprised by how difficult it would be to hold the guides straight for soldering.
I shouldn’t have been surprised. Indeed, when I built #10, I anticipated this problem, and designed the cylinders with a built-in jig to help get them straight. This time, I didn’t have the same foresight. I had to create a jig after the fact, instead.
The jig is shown as the left-most element of the photo. It slides into the crosshead guides and locates them relative to the holes at the front and the back of the cylinders. Once put together, the assembly is quite rigid even without solder. I Sharpied it up to help keep it from getting soldered permanently in place.
The hole in the cylinder front will be capped with a little button after the piston rods have been cut to length. Speaking of holes, so far, I’ve left off the cylinder cocks; I hope I remember them!