Re: Tractive effort, horsepower, and tractive power

Hi,

Tractive Effort is the force a locomotive can supply to moving a train.

When I wrote my book for Live Steamers, the resistance to movement by a car is what the TE must overcome.

IIRC, depending on track conditions, it might take 10 pounds of TE force to move one ton of car (gross weight) on level ground with straight track and good track. If the track is in bad shape (grass growing in it and so forth), it might take 20 pounds of TE to move the same gross weight of car.

Grades are another form of rolling resistance. If a loco can pull 100 cars on level ground straight track, it may only be able to pull 50 cars on a 1% grade and 25 cars on a 2% grade and only 11 cars on a 14% grade. (I remember this example from long ago and do not recall the specifics so I might be off a little). This woould mean that to move the same ton of car weight on level track would take 10 pounds of TE, on a 1% grade it would take 20 pounds of TE and on a 4% grade would take 40 pounds of TE.

Curves also add to rolling resistance that requires TE to overcome. This is why a grade can be lowered on a curve to keep the same TE required to pull the same weight of car.

I'll look and see if I have the short explanation of rolling resistance and TE from my book in a text form. If I do, I'll be glade to publish it here for you.

Doug vV