I have one of the Bachmann Hershey trolleys. It was running poorly so I figured I would take it apart and see if I could restore it to health. What I discovered: The drive unit comes out with two screws removed from the bottom. It is a complete, self contained drive with wheel power pickup wipers built onto the drive. The drive unit will work, DC, by itself. It is 3 3/4" long by 7/8" tall. Relatively flat across the top. The motor wires, and brushes are easily acessable from the top. (Looks kind of strange going around the layout just by itself.) The wipers rub on the top of the wheels. The motor is open frame, with worm gears to each axle. This looks to be a great drive unit for S&B. Take a truck off a flat car, cut a hole in the deck of the flatcar to fit over the drive, and you have a great platform to bash a loco on, or a speeder, or what ever your imagination can come up with. It looks like the deck of the flat car will be about flush with the top of the drive, and you already have the couplers installed. Another possible is a small switch engine. Just bash a body and set it on top. It would leave you with plenty of room for weights and a decoder. AND, it's relatively cheap, and readily available!!!! Let me know what other ideas you can come up with.