Re: Tractive effort, horsepower, and tractive power

hoghead1 Wrote:
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> . . .  Not to add to the confusion, but TE is more
> a measure of how much weight the engine can
> set in motion, forget speed.  HP is a measure of
> what a locomotive can haul at speed.


. . .  The latter, in the case of a steam locomotive, being dependent on 'Boiler Horsepower' - how fast can the boiler turn water into steam at a high enough pressure to move the weight of the train.  "Modern" steam locomotives with bigger fireboxes - like a 2-8-4, 2-10-4 or 4-8-4 - could boil water faster, and usually at a higher pressure, so they could not only pull the train faster without running out of steam, the higher pressure also provided more sheer pulling power (more tractive effort).  Thus a 2-8-2 with 63" drivers might have a little more tractive effort than a 2-8-4 with 69" drivers, but the 2-8-4's bigger firebox would produce steam faster and allow it to haul a slightly lighter train a lot faster.

(Added 07/15)   Another example: C.P.'s El Gobernador 4-10-0 could get a fairly heavy train started (high tractive effort), but it's small firebox couldn't boil water fast enough to keep the train moving, and it would run out of steam after just a mile or two (low horsepower).  The engine was an embarrassing failure, and IIRC it was scrapped within a month or two of being built.

- El Abuelo Histœrico, Greengo y Curmudgeoño de los Locomoturas Viejos y Verdes,
aka Der Grossväterlich DünkelOlivGrünDampfKesselMantelLiebHabender



Edited 2 time(s). Last edit at 07/15/2016 10:46PM by Russo Loco.