What is the benefit of using multiple engines to a single train?

Question

Is it possible to run more than one engine for a single train, how do they balance between working of two engines ...If so What are the benefits of using multiple engines...

Answer 1

Trains are operated with more than one engine all the time.  They are either in the form of a "helper" engine, located further back in the train run by a separate engineer, or as "Distributed Power" in the form of an unmanned engine back in the train that is controlled via radio signal be the engineer on the "road engine."

In addition to providing additional power for grade territory operations, by handling some of the trailing tonnage it reduces the amount of force on the draw bar right behind the road engine and all the others closer to the head end.

Either way, multiple unit helpers can be found right on the rear of the train, or cut-in nearer the rear end.  The power is distributed by mathematical formula, wherein a helper cut-in the train should be positioned such that, of the total amount of tonnage the helper will handle, it is shoving one third and pulling two thirds.  This keeps the helper power from shoving the cars immediately ahead off the track.

There is often confusion because terms are often interchanged, that shouldn't be.  An "engine" is: A unit propelled by any form of energy, or a combination of units operated from a single control, used in train or yard service.

The "diesel engine" that turns the alternator on a unit is called the "prime mover."  People often incorrectly interchange these terms which causes the confusion.

Answer 2

I'm not positive as to what your asking but i'll give it a shot.A train can run up to 8 locomotives at one time.They are all MU'ed by air and electrical connections so that they are controlled from the lead unit by the engineer.All locomotives when they are running properly put out about the same amperage to the traction motors.A railroad bases the amount of engines used based on the terrain the train has to traverse and how fast they want it to be able to do so.The more a train weighs the more power it needs.A typical manifest train is run with about 1.5 -2.0 horsepower per ton. So say the train weighs 8,000 tons and you are using 4,000 horsepower units you would need 4 of them to get the 2.0 HPT figure.

I see now you meant engines at both ends of a train so heres an answer that explains that.That is known as DPU or distributed power.The rear engines are pushers that are controlled by the engineer on the head unit.They are electronically linked by radio control.They can be run linked so that the pushers do whatever the head end power is doing or they can be run split screen.In split screen the engineer runs the units separately from each other.For example he can have the head end in dynamic brake and have the rear consist pushing.They use DPU because it greatly reduces buff and draft forces in heavy trains like coal trains that can weigh 20,000 tons.It also allows trains to be run using less power than they would need if all the units were on the head end.

Answer 3

The diesel engines on the train run electric generators which power  the train so they are easier to balance. The more engines the more power with less wheel slippage.  

Answer 4

When engines work in multiple, all the electrical and braking equipment on the engines is connected via hoses and cables between the locomotives and the whole formation can be driven from the cab of the leading engine.

Heavier trains are often beyond the capacity of one locomotive so coupling two or more in multiple means double or more the tractive effort.

NB in steam days the locomotives could not work in multiple, that is, they could be coupled together to head a train, but each loco had its own crew who had to synchronise their driving with the other. This was done by signalling from one to the other with the whistle.

Answer 5

Among the reasons already listed here sometimes they run the engines back to back in pairs even the train could have been pulled by one unit so they do not have to turn the engines around for the return trip.