Although I have seen no empirical evidence of this that I can point to, I agree with Byron on this. Superelevation on our models is great for realism, especially in photography, but when on grades and with substantial trailing tonnage, or even on level curves with strong resistance in the train behind the locomotive, you get increased forces pulling the couplers inward toward the center of the circle the more you super-elevate.
Great to look at, but just another variable that can work against you in hidden, hard to reach trackage. My helix tracks were level across them. Worked very well.
can’t the wheels, when offset from the centerline of the rail, where the outer and inner wheel travel a different distance because of their slightly conic shape move across the curved rails without any undo friction?
and when you consider both the centripedal and the force pulling the car toward the center of the curve due to the uneven superelevated rails balance one another at one speed for curves of sufficient radius?