Fitting a motor unit into a kit that the manufacturer hasn't considered is always going to be a dive into the unknown. In 3mm scale this is something you just have to get used to - maybe someone has built the kit before you and written up their experience but probably not. More likely the model has been built but its inner workings will remain the builders secret.
Not here ! I knew the Bullant bogie would fit as I'd unpacked several of them on the stand and held the units up against the etched parts to see what would fit. Wheelbase was immaterial as these would be nicely hidden away behind the side skirts. I just wanted the whirly bits inside to be as hidden as possible.
Having chosen my unit, I tested it out on the workbench and then took it to pieces. Bye bye warranty.
There is method in my madness - the bogie is intended to pivot on the butterfly shaped bit of metal so you can use it in a DMU or similar. This sort of thing won't do though when in use as a tram - we don't want Toby spinning on his axis do we ?
The parts separate easily enough with the aid of a small screwdriver and unsoldering the pickup wires. The units themselves employ a clever modular construction which allows the manufacturer to produce different combinations of length and numbers of wheels. In fact if they would just sell the bits, I'm sure we could all manage to make our own. Doubtless with someone making up special versions with 12 wheels !