"...what part of the train is always going backwards..."

Ok, ok. I asked this question with a lead-in like, "Speaking of flanges..." so I just assumed that you'd get the picture that something about the flanges always goes in the opposite direction to the train.

Because the axle is moving with the train and at the same velocity, and because the wheel is in direct contact with the rail and not moving, the outermost edge of the flange (which extends BELOW the contact point of the wheel with the rail) moves opposite to the train's direction. It's simple geometry.

Because the trainman's union cannot control this backward motion of the flange, it compensates by insuring the forward motion of employees' paychecks. Always.

Flanges have nothing to do with keeping the train on the rails while it is underway. (If they did, they'd be worn down in no time and your ears would be dead from all the screeching and grinding -- sorta like riding the "T" under Boston...) Flanges keep the train on the rails when it's sitting still. Thus, this magic process I'm teasing you about is a dynamic process.

Let me ask you this: How does your car negotiate the bends in the road? No rocket science here, just a common-sense answer......