After the mostly successful completion of the 1st prototype of the Clayton locomotive I made some changes to the design to solve the problems I encountered as well as to make the loco easier to assemble. The parts for this 2nd prototype turned up today. As you can see I've doubled the number of components from two to four and not everything is printed in FUD.
One of the main design changes was to allow the axles to be completely assembled before fitting to the model which led me to the idea of a keeper plate, which also has the advantage of stopping the axles from shifting sideways which is what was causing the jumpy motion on the last prototype. Now I could have had the keeper plate printed in FUD but instead I've had it printed in stainless steel as this nicely adds weight to the loco; 7g of extra weight to be precise. The only problem is that the steel is exceptionally tough and the holes for the screws that will hold it in place ended up printing slightly under size. Opening them out has caused me to break a drill bit, draw blood, and I now have a blister but.... everything now seems to fit together!
I also made the control box as a separate piece so that not only is it easier to paint the model but it can hide the nut that holds the upper and lower parts of the model together. Unfortunately the footplate is still a little bowed and while I did make the fit tighter at the front it's still not perfect so unless I can flatten the part out a little (soak in hot water then hold flat while it dries) I might need to think about a better fixing at the front as well (harder as the pulley for the drive belt is in the way).
I've had to start packing most of my modelling stuff away as we are having family to stay at the weekend so I'm not sure when I'll get to try and put this together but hopefully I'll be able to find some time to at least assemble the axles and make sure the keeper plate works properly.