I have used the gearset I removed from the Y14 to build a new gearbox. The other parts here are a fold-up gearbox from Connoisseur Models (Jim McGeown) and a secondhand Mashima 1830 motor I found on eBay.
The Mashima motors are still useful because, unlike the Canon CN22, their mounting holes line up with the holes in these gearbox etches.

My method of assembly here is completely different to that suggested in the instructions but I think it makes for a potentially more accurate job. I began by opening out the axle holes in the frame and the washers to let an axle pass through with a tight freehand push fit. The five-sided broach keeps things symmetrical.
Then I soldered the washers to the inside of the frame - I want to make the assembly as slender as I can. Temporary electrical connection for RSU.

The two sides of the gearbox are each folded up to a true right angle, one at a time, and secured using the angle strips supplied on the fret.

The ends of the gearbox are folded up and soldered along all edges, and the outside corners dressed.
With the gearbox as solid as it can be, the two axle holes are teased out (5-sided broach again) to give a decent running clearance for the axle. The axle is inserted and the worm gear located using some packing washers, a Slater's axle bush and the inevitable shim washer.

After a test fit of the motor, the two mounting slots are filed slightly longer to allow a closer mesh between the gears.

The motor is installed, the gears are meshed correctly (slacken one fixing screw and twist the motor) and the gearbox is test run. Everything is smooth and quiet, and I lubricated the gears and the holes where the axle passes through the gearbox.
The important thing is to make the angle beween the motor spindle and the axle as close to a right angle as you possibly can. If there is a skew here then the worm gear (being the softer of the two) will wear very quickly.
I am happy with this one, so I can put it aside for a future loco and I cannot lose the gears or the motor in the meantime
