hertsbob wrote:Is there a purpose to the cross-hatching on whatever the thing is that's got cross-hatching on?
You mean the strange nut on the cylinder piston crosshead? That's a multi-keyed nut, a Union Pacific design that was meant to be more robust than a standard cotter pin. There's meant to be something that looks like a giant wire paper clip placed in the grooves and it stops the nut from coming loose even when there's a lot of vibration. I've modelled the grooves but I still have to put in the "paper clip".