If you have an old mouse sitting around, you'll find that cutting its "tail" off and stripping it down will yield some very flexible wire for virtually no cost. You may still want even more flexible wire for N scale. In addition to David's suggestion, Northwest Shortline and Ngineering also offer ultra flexible small gauge wire.
You may want to reconsider metal wipers if they're made from stamped metal. I tried some Tomar ones in HO without really good results, so suspect it would be a challenge to make 'em work in N. Some narrowgauge buddies helped me with putting wipers on brass steam, suggesting using Tichy #1101 .010" phosphor bronze wire to make them up. We usually use a small mount pad made from a small bit of PCB stock cut from the tie stock made for handlaying turnouts. The wiper wire and feeder is soldered to one side and the other side can be glued or soldered to hold it in place. The PCB insulation keeps all the electrons on the proper side of the fence. They're very low drag compared to the wipers made from stamped metal I've seen.
Another good thing with the wipers made from Tichy P-B wire is that you can squeeze wipers for both sides of the circuit on each truck. Getting good contact really helps a successful sound installation. The more wipers, the more reliable the contact and sound. Since I was just doing lighting and had room for a big fat capacitor in the car, I only put wipers on one side of this truck.
You can add a second mounting pad on the other side of the bolster and have it wipe the back of the wheels to pickup from the opposite rail, which is what I do on loco tenders. These wipe the top of the wheel tread, so aren't easy to see in this pic.
Be sure and leave a small bit of slack, enough to accomodate the truck's turning, in the feeder wires between the truck and body.
Mike Lehman
Urbana, IL
I bought a 60ft boxcar so that I could cram all the electronics for the soundtrax soundcar decoder. I bought metal wheels and metal wipers for power. The only problem that I am seeing is how to hook the wires through the frame to the wipers so as to not hinder turning. The truck pin on microtrains isn't hollow so I am at a stand still can I can figure this out.
Has anybody done this on a micro trains boxcar. Please let me know how you did it. Thanks