Reading a very old copy of model engineer the other day, one of Martin Evans 5" plans. Despite looking through several copies I couldn't find anywhere about the profile the wheels should be finished with, in particular the edges which are in contact with the rail.
I've got the round without corners profile
the axle hole and the back of the wheel machined and the overall outside diameter dimension plus a bit for machining "the finished profile"
But can't find any reference to the contact patch.
Pete