"Linda" - gearbox and motor mount progress

Well, after a long interlude for a holiday in the USA and a few other things, I achieved a smooth rolling chassis. It had a slight bind for a long time which I think was down to:
1. The cranks which I thought were firmly attached, actually weren't. It seems that one of them moved slightly on every revolution. A tiny dab of Loctite B638 retainer solved this.
2. One of the front bearings was slightly too far back in the frames - it was set up with the coupling rod and an alignment jig and pulled forward slightly.

I've now started on the gearbox. I have to confess that I can't actually find the instructions at the moment (that accounts for a lot!) but I think the advice is to glue the motor into the gearbox. I din't like this as I'm more than likely to get it wrong, and it's not adjustable/removable for mesh or maintenance. The little coreless motor has a threaded boss on the front and I'd originally cooked up a rather rough arrangement with a thin nut soldered onto the gearbox etch and the motor screwed into that. I recently stripped down most of the gearbox and replaced it with what you see below.

I've made a small nut (although it doesn't look like one, as it has no flats and concave sides) to attach the motor to the gearbox. The strange shape is because it's dished to only just clear the large idler gear - space is very tight here. It's made from a nut from an old miniature toggle switch, i.e. the nut which is used to clamp the switch into a control panel via a threaded boss. The next photo shows a similar nut and the mandrel I made up from a very mangy old switch to turn down the motor mounting nut. The nut will eventually have a couple of notches to make it easier to tighten up. If you attempt anything similar, beware - these small switches have a wide variety of different thread diameters and pitches, and there doesn't seem to be a standard. I just happened to get lucky and find one with the same thread (I've no idea what standard it is but it's about 5mm diameter).

Lastly, a grainy photo (not sure what happened there) or the motor, nut and the idler shaft. The latter is a bit of 2mm silver steel tapped 8BA at one end and with a head soldered onto the other, to make the whole thing removable. It has a little 1.0mm brass bush to stop the gear wandering sideways out of mesh.