So I've made a bit of neutral progress this evening. A step forwards in that I fixed the gear wheel on the 2nd bogie in place, after shaving a bit off the Delrin sprocket so that the brass gear wheel would sit centrally in line with the motor shaft. I also fitted the chain, then removed it & took a link out as it was too slack. After about half an hour fiddling, I finally got it back on, & it's nice & tight. Does anyone have an easy method of connecting Delrin chain?

But there was also a step backwards. Turning to the completed bogie, I used a bit of bearing lock to fix a loose Delrin sprocket on the driven (I.e. not the motored) axle. In doing so, I managed to glue the brass bearing to the axle, and in turn loosened it in the bogie frame. I managed to get it all free and apart, and cleaned up ready for reassembly, but with all the handling, one of the sideframes came loose, so I took it off.

I then turned to the motored axle. The gear wheel on this axle is also not in line with themotor shaft, so I unscrewed the wheel with the intention of getting the gear wheel & sprocket off and shaving a bit off the sprocket so that the gear wheel can be centred under the motor properly. However,  I can't budge the sprocket, and if it try too hard, the frames will bend. Both wheels are off, its just the axle in the frames with gear wheel & sprocket on it. I just cant get enough purchase on the axle & sprocket to move the sprocket along the axleto get it off. That's where I stopped for the evening.