Modern Atlas 100 Ton roller bearing trucks have both wheels insulated from the axle with a Delrin or Nylon bushing in each wheel. Therefore, each wheel is fully insulated from the cast metal sideframe/axle. You will need to have the wiper rub on the backs of any of the wheels (not the axle) that you want to pickup power from the rails. If you attach the wiper directly to the bolster, then the cast metal truck assembly will be live with track power from that rail but as long as you only pickup power from one rail per truck, then that should work. Please note, however, that this assumes that the car that the trucks attach to has a plastic frame. Using this scenario on a car that has a metal frame will cause a short circuit through the frame that the trucks attach to since it will be common to both trucks which would have opposite polarities.
Scott
