I see these figures for diesel and electric locomotives, "continuous tractive effort" and "starting tractive effort". But what exactly is the difference? How long / up to what speed / whatever the deciding factor is, can I use starting TE? If I need to know whether a train of known tonnage will stall on a grade, do I care about my loco's continuous or starting rating?
Triplex, the terms define the length of time and amount of electrical current that can be applied to the axle traction motors. Tractive effort for each wheel set is controlled by the amount of current applied to the traction motor. The more current applied, the more tractive effort results, until the wheels slip. However current also heats up the motor, so the more current, the hotter the motor becomes. Therefore Starting Tractive Effort (electrical current) can only be applied for a fixed amount of time before the motor overheats, usually less than an hour. Whereas Continuous Tractive Effort (electrical current) can be applied continuously for hours, even days without damaging the motor because its cooling fans can dissipate the heat.
Well written Hytec! This all gets rather complex and beyond my complete understanding. I recall reading somewhere that the curve of diesel locomotive pulling power declines at higher speeds, explaining the need for more power on fast trains. Too, I think the power curves between steam and diesel are inverted. Diesels excel in starting heavy trains, but not so steam. Yet, steam locomotives develop increasing power at higher speeds. Triplex, see if you can find a used copy of the thin softcover book The Diesel from D to L by Vernon Smith, published 1979. It's packed with great technical information, is very well written and should be inexpensive.
I can make it even easier. In a diesel electric, particularly AC drive, starting tractive effort is 100% meaningless and nobody in the real world ever uses it ever. You build a train based on the CTE.
