How fast can trains turn bends?

Question

How fast can trains turn around relatively sharp bends without the risk of derailment? In particular, First Great Westerns trains. (Assuming passenger comfort is unimportant).

Answer 1

Speed restrictions on curves are for passenger comfort. The speed at which a train would overturn is considerably in excess of this. In 1972 there was a derailment at Eltham (Well Hall) in southeast London when a train overturned after entering a 20 mph restricted curve at 65 mph. A calculation showed that the theoretical overturning speed was 63 mph and even then, allowance was made for track distortion sharpening the curve.

That doesn't necessarily mean that all trains could negotiate curves three times faster. The track conditions and the train's weight distribution play a part, but it gives you a rough idea.

Answer 2

This depends on many things - the weight of the train, how long it is, how (or if) the track is banked, how sharp the curve is, weather (excessive heat causes track to deform), and how well the track is maintained.

Most rail services restrict speed between 55-75mph and slower if a problem is expected - every curve will have a different theoretical maximum (laws of physics have many variables) but they make the speed limits somewhat concervative.

Answer 3

The track is banked, just like highway or racetrack curves.

The greater the maximum speed the higher the outer rail is elevated from the inside lower rail.

It is very precisely controlled and checked almost daily to make sure the proper elevation is maintained.

It is this elevation that assures passenger comfort. Without it your journey would have to be much longer as the speeds would be greatly reduced.