My old railroad had banked curves. They were not correct as far a prototype standards, but they worked. All of my track was ballasted to cork roadbed. I used a sanding block and sanded the inside of the curves away a little bit on the roadbed before I put the track down. My method worked fine. I never had a problem with it. I just could hardly tell that it was banked. I realized that the next time I would have to bank it more, and that may begin to cause problems. I figured it was not worth the chance of causing derailments with larger banks when building my new railroad.
I have read about banking in a book. I think it was in "Track Planning For Realistic Operation" by John Armstrong, but I am not sure.
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Elias Valley Railroad (N-scale)
www.geocities.com/evrr