Keeping a Steam Engine Under Control on a Long Downgrade

[BaltACD]

What truly makes a Engineer is the ability to use the braking power available to safely move trains over the grades on a territory. Most ‘idiots’ can operate the throttle, only an Engineer can operate the brakes.

[erikem]

NTSB in it’s testing of a CSX runaway derailment on 17 Mile Grade back in 2000, determined that 15 MPH was the maximum speed that air brakes alone had sufficient stopping power to bring a train to a stop without overheating the braking equipment (brake shoes & wheels) to the point of fading. Note-this is based on 286K cars with state of the art high friction composite brake shoes - neither of which existed in the steam era.

It should be noted that pertained to that particular stretch of railroad.

True, but at 2.2% it is representative of most mountain grade routes still in operation so it is a good benchmark.

Mac

From reading the NTSB report, I would also think that the grade % is the critical issue for speed as opposed it being a particular stretch of railroad. The physics would imply that the speed is limited by keeping the wheel tread temperature below ~600F to prevent brake fade. I would assume that the 315k cars would be limited to an even lower speed, though a larger wheel diameter may allow for less of s speed reduction.

The issue of car weight, gradient, bake shoe type and wheel diameter would make for a good discussion in its own right.

BTW, the Milwaukee’s electrification was the first demonstration of the advantages of regenerative/dynamic braking for mountain railroading. The reports on train handling stated that brake wear was substantially reduced, safety improved and increased comfort for the passengers. The reports also hinted that the reduction in brake wear as well as wear and tear on the car was a greater cost savings than the value of the regenerated electricity.

• Erik