It has taken a long time, and I have had to re-lay some of the track, but I can finally show the model Stanier 8F locomotive pulling a fairly long train of coal wagon around my model of a colliery.
This shows my 7mm scale, Scale-Seven, model of a Stanier 8F 2-8-0 freight locomotive running around my model colliery. The track is a bit rough, and I had to relay some of it to allow the eight-coupled (long fixed wheelbase) locomotive to go around the curves, and up and down the gradients I have made in the model.
In fact at the moment, I can make the engine and wagons go around the loop in an anti-clockwise direction, but if I try to have it run around clockwise, it comes off the rails!
However I suspect that the problem is with the track work, rather than the engine which I made.