With the wheel inserts in, getting the chassis working is simply a matter of fitting the bolts, and slotting on the rods.
Lengths of plastic tube act as bearings. These replace resin parts from earlier kits that were too small, and very brittle when you tried to drill them out. I know my dad's original chassis is fitted with plastic tubes, because I brok three of the five provided doing just that!
While plastic tube might not sound that impressive, we are talking about a chassis designed for light loads. The tube stops the metal bolts wearing away the 3D printed rods, and should be able to do this for a long time. If this becomes an issue, I'll replace them with bits of brass.
I like these chassis. They are quick and easy to assemble. OK, if you need a loco with a lot of grunt, they won't do the job, but for the sort of light loads trunding around a garden railway the model is likley to haul, it's underpinnings are fine.