The fixed wheels, plus the bevel create a self-centering effect.
As the wheels move off centre, the bevel makes one wheel have a larger effective diameter and the other wheel a smaller effective diameter. Because the wheels have a solid axel, that forces one wheel to start travelling slightly faster than the other, causing the pair of wheels to turn.
With the bevel making the wheels larger on the inside, it means that as a pair of wheels drifts right relative to the tracks, the right hand wheel rides up, starts behaving as if it’s larger, and then starts to overtake the left wheel (which has ridden down, and behaves as if it’s smaller), creating a turning effect to the left, correcting the rightward drift.
When setup correctly, and travelling at a reasonable speed, the big metal lip on train wheels should never touch the track. The self-centering effect does all the work, the lip is just a backup to deal with overly tight turns, points and extremely slow running.
As the wheels move off centre, the bevel makes one wheel have a larger effective diameter and the other wheel a smaller effective diameter. Because the wheels have a solid axel, that forces one wheel to start travelling slightly faster than the other, causing the pair of wheels to turn.
With the bevel making the wheels larger on the inside, it means that as a pair of wheels drifts right relative to the tracks, the right hand wheel rides up, starts behaving as if it’s larger, and then starts to overtake the left wheel (which has ridden down, and behaves as if it’s smaller), creating a turning effect to the left, correcting the rightward drift.
When setup correctly, and travelling at a reasonable speed, the big metal lip on train wheels should never touch the track. The self-centering effect does all the work, the lip is just a backup to deal with overly tight turns, points and extremely slow running.