Ok, will do some reaearch on that, thank you. I might just have to give up on the whole idea and buy a jockey wheel to bolt on to the a frame but I have hope.
On a similar note, I'm trying to repair a trailer jockey wheel clamp by welding a nut over the bolt hole to provide a thread for the bolt. The body of the coupling is cast while the nut is mild steel. Had a go last night and as soon as I tightened the bolt it popped off. Looking at the weld I...