Our Welsh Pony is back in business after a successful wheel transplant.
Himself reports that the loco now runs more smoothly and without the notable lurch it had before.
Closer inspection of the old wheel sets suggests that the problem was not a driving wheel which had the axle hole off-centre, as we suspected, but a tyre which was not a perfect circle.
The shot above reminds us what a lovely looking model the Mercian Kit made before it was withdrawn from sale - it's a shame the chassis / gearbox design was such a horror show.
As I recall, it was impossible to fit the components provided with the kit into the space available and Himself bodged it up with a replacement gearbox.
I suppose our Pony will have to be put to one side until we see what the real one looks like when it's finished - fingers crossed it will happen in its 150th anniversary year.