Re: Steam builds for Alice to Darwin rail link

[Eddie Oliver <eoliver@efs.mq.edu.au>]

Greg Wickham wrote:

> What is a 'momentum grade'?

A grade such that a train conveying full load requires to approach the
grade at some minimum speed, so that it has enough "momentum" to
surmount the grade (but where the motive power would not be powerful
enough to surmount the grade with that load from a standing start).

Thus for instance a locomotive may be able to haul (say) 500 tonnes up a
certain grade from a standing start, but may be able to cope with 700
tonnes on the same grade if it can approach it at a minimum speed of 50
km/h.

Momentum grades are usually short, but allow greater loads to be hauled
over a given section than would otherwise be the case. The disadvantage
is, of course, that the train will not surmount the grade if it is
prevented from going fast enough on approach. Thus if (for instance)
trackwork is in progress, the loads over the section may need to be
reduced, or assistant locos may need to be provided.

Eddie Oliver