Those who are observant, will have noted the jaunty angle that the return crank is sat at, in the top photo of the post with the sand pipes fitted. Having had this pointed out by someone this came back to bite me.

Initially I just thought that in lifting the loco up I had dislodged it causing it to unscrew and come loose. However no matter how much I tried I couldn’t get it to tighten back up in the right place. I tried shortening the bush but realised too late that the crank pin itself must have shifted in the wheel. Then having shortened it I found that when tight it was nipping the conrod and coupling rods so that they wouldn’t move.

Making a replacement bush was the order of the day.