How much weight can a new train engine pull?

Question

I was just wondering how much weight an engine can pull before they have to add another engine to the train. If you know could you also tell me how many cars also.

Answer 1

Alexandria  is certainly on the right track  (no pun intended).   New or old doesn't really play into the equation as does the horse power and weight of the locomotive, and the number of driving axles.

On level terrain, one could handle a given amount of tonnage at a load of maybe 3/4 horse power per trailing ton, but lets simplify the math, and allow for a minimum of one HP per ton, which is actually a reasonable HP to ton ratio.  You wouldn't make much speed, but you could start and keep the tonnage moving.   Assuming we are speaking of a single 6000 HP locomotive, it would theoretically pull 6000 tons.

Ascending grade of course requires a higher HP to ton ratio.  There is a nifty little formula for calculating at what speed a given tonnage will climb a grade, which is called the "rolling train resistence formula".  It is quite simple.  Determine the horse power per ton ( HPT ), multiply by 12, then divide by the percentage of the grade ( %G ), and this will result in the speed at which the tonnage can ascend.  Expressed in other fashion,  HPT x 12 / %G = S.

Some locomotives have a "short time rating".  The harder the locomotive must work, the higher the ampereage to keep the wheels turning.  Again, with the typical DC locomotive, when you get down around 12 to 13 MPH at full throttle, you are well into the short time rating, meaning without a change in speed you are probably looking at about ten minutes before the locomotive will start burning up the traction motors.  When this time is reached, the train must stop to allow the traction motors to cool before resuming movement.   Using the above formula, if your calculations determine the speed wil be this slow, then that tells you you must add more power to avoid getting in to short time.

As far as a number of cars, this is not useful information, at least where POWER is concerned, because the tonnage is the determinig factor.  The number of the freight cars, or more correctly the length of the freight cars, is quite important when determining the braking calculations, but this is another question, so ask and I will try to answer.  Freight cars can run anywhere from 35 tons or so for an empty, smaller car, up 145 tons or so for a typical bulkhead flat loaded with milled lumber.  With special duty cars, the tonnage of a single car can be much more.

Hope this clarifies it for you.  While on the subject of locomotives running around with all this tonnage, please keep yourself out of the way.  Only you can put yourself in danger.  If I can see you, it is already too late to stop for you...........

Answer 2

3 units can pull 6500 tons so approximately 2200 tons.  But this changes depends on the route of the train.  If uphill route, then 4 units to 6500 tons/