how does a locomotive pull such long loads on the rails?

Question

how is it possible for a locomotive to pull such heavy loads on a train track that sometimes is over 4 miles long . And how do they connect locomotives 2 or 3 together for power

Answer 1

A locomotive's ability to pull loads has as much to do with the tractive effort (in today's diesel-electrics the term is usually adhesion) it exerts as the horsepower it is capable of (not much point of having, say, 5000+ horsepower if one has no tractive abilities). So, a high tractive effort, coupled with decent horsepower (say, 3000+) means the locomotive can pull a substantial amount of weight.

As for locomotives being coupled together typically they are "MU'ed," meaning that the lead locomotive can control all other locomotives in the consist.

Answer 2

First, to address multiple units, this is done through electric jumper cables. The locomotives are built with the ability to be "MU'ed" together and to be controlled from one unit. There are multiple cables that give the engineer control of the systems of all the units (sanders, lights, etc..). The throttles are all run in unison; once the throttle in the controlling unit is advanced to run 1 for instance, the trailing units will also come up to run 1 and start to pull as well -- sometimes it can make for some interesting hauls if you have a slow loading unit in the consist.

Traction is achieved through track adhesion, tractive effort, tractive force, whatever you wish to call it. All that horsepower isn't any good unless the locomotive has good tractive effort. I don't have exact figures but a locomotive of say 5000hp may have 85,000lbs of tractive effort.

Determining how many locomotives per train is based on a horse-power per ton ratio which varies route to route and railroad to railroad.

P.S."Gentlemanfarmers" info is quite a bit off. The diesel engine in a diesel electric locomotive powers one main generator which supplies electricity for the traction motors. It has *nothing* to do with "electro magnetic traction" as there's no such thing on locomotives.

Answer 3

When diesels are coupled together for power, they become one locomotive with one engineer with high amounts of horse power. I've seen a train on the pre-merger ATSF that had 8 locomotives with a combined horse power rating of about 35,200 horse power (Each locomotive had 4400 HP). this goes to prove, if you have enough horse power, you can move anything.

Answer 4

Electro-magnetic traction. The diesel engines power generators that create magnetic force through the wheels of the locomotive to the tracks giving it superior traction.

Answer 5

Simialr to trailers, ie making the breaklights work on both wheeled platforms. And the imense weight of the locomotive puts down enough friction so the horespower of the locomotives will be able to do its job.