The 45xx has been gradually progressing over the last week or so. The chassis now runs ok - simply tightening up the coupling rods sorted most of the issues!
The 'wheel arches' (what else do you call the spaces for the axles in a solid chassis block?!) required a bit of work with a round file to get all the wheels level and in full contact with the rails. Not sure if it was wonky out of the box or if it's something to do with the work I've done on the chassis.
(As an aside - while Bachmann clearly don't go as far as putting any form of proper compensation on their models, there is plenty of vertical 'slop' in the way the wheelsets locate into the chassis, meaning that you have a sort of poor man's compensation as I pointed out before - which I think is fine at least for relatively slow running speeds and well-laid track.)
The 're-purposed' Bachmann pickups seem to be fine. One silly thing that's puzzling me at the moment is how to reconnect the wires from the pickups to the motor so they are still easily detachable if I need to take everything apart again. Ideally I need very small terminal blocks but not sure if you can get them small enough or where from... anyone got any suggestions?
I've made a start adding the brakes (the original mouldings were removed from the Bachmann baseplate before it was cut up for use in the new baseplate - if I'd just left them on they would have stuck out too far). I cut small strips of plasticard (1mm X 1mm x 5mm) and glued these (using Loctite 'All Plastics' superglue) almost vertically onto the baseplate sides where the brakes were to be located, overhanging the bottom edge by about 2mm. These are to attach the brake mouldings to so they're positioned the correct distance from the chassis and line up with the wheels.
Glueing the brake mouldings onto these strips is quite fiddly as you need to do it with the wheels in place to get them properly lined up. I marked in pencil on the chassis sides where the tops of the brake mouldings should come up to just as a visual reference to try to get them all the same height (some sort of jig might help here). The glue goes off almost immediately the two pieces touch so you have to try and line them up a millimetre or so away and then press down - quite tricky when you're working with tweezers and trying to avoid getting the glue everywhere - especially on the wheels! Again, maybe some sort of jig would come in handy but I'm not sure exactly what.
Once these are all on I can start thinking about painting the chassis and then putting it all back together!