I’m starting to get the hang of parameterized CAD with OnShape. Tonight, I managed to get a pretty good sketch of the locomotive frame, and extruded it to make the outside layers.
I also discovered a handy feature called a variable, which enables you to label a dimension, such as the standard thickness of metal, and then you can use that variable anywhere a number is required. Thus if you discover the metal is going to be a different thickness, you only have to update one location.
I’m still struggling with assembly of parts. While the drivers look like they’re in the right position above, it is only because I moved them there. The rear ones are perfectly happy to move longitudinally in the frame, rather than up and down. Also, I have no idea what I’m doing wrong with limits; so far they don’t work for me, and those bearings can slide right through the drivers like a couple of ghosts.
If you want to follow along, or even make your own 4-4-0 drawing, the drawing is here.