How many car motors would it take to run a train?

Question

How many car motors would it take to run a train?

Answer 1

Hard to say, trains run off of motors ( electric) Cars run off engines (Internal combustion) Trains get electricity for their motors thru diesel generators and batteries.

Answer 2

One could do it if you didnt want to go fast

Answer 3

100

Answer 4

Loaded question, actually, with a complicated answer.   I'll try.

It is not just horsepower that determines a locomotive's ability to "start" a given tonnage or keep it moving once started.   "Tractive effort" ('torque', as applied to an automobile engine) is key to the equation.   What is the equation?   Good question.

Let's consider the definition of "one horsepower (HP)".   One horsepower is the amount of energy needed to raise one ton, vertically, one foot in one minute.   As I have given the "rolling train resistance formula", those who have seen it know how horsepower comes into play when determining the amount of power to ascend a grade.

The thing that makes diesel electric locomotives much more attractive than steam, other than the obvious high cost of maintenance and operation, a diesel electric locomotive can start more tonnage moving than a steam engine (or multiple steam engines coupled together) can start.   The perfect hybrid would be steam and diesel electric together, the steam engine being able to keep more tonnage moving after started than the diesel electric.   Put simply, a diesel electric will start more tonnage than it can pull, while a steam engine can pull more tonnage than it can start.   Sounds odd, but true.   Of course, during a slow drag up a hill, which the diesel will handle at lower speeds, with the advantage of tractive effort again coming into play, a steam engine is likely to stall.

So, the "prime mover", which is the diesel engine, turns a generator (more and more locomotives are showing up operating on Alternating Current, in which case there is an alternator instead), quite a large one at that, that provides power for the axel hung traction motors on the locomotive's truck.

Most older EMD DC locomotives, designed for freight service, have a gear ratio of 62/15 between the pinion gear on the motor's armature, and the ring gear connected to the wheel.   This gearing, again, allows for maximum starting tractive effort.   Higher geared locomotives are found in passenger service so they can travel at higher speed, where the starting tractive effort is not as crucial, given the relatively light tonnage involved in this application.

I told you it was a long answer, but were about done.

When dealing with horsepower, there is an electrical equivalent to one HP as defined above, which I believe is 715 watts.   (An electrician can correct us on this).   This is your multiplier in determining electrical energy needed to lift a train, or get it moving.   Fortunately, for us non "electrical engineering" types, there is a much easier formula.

Horsepower per ton, multiplied by 12, divided by the percentage of grade, will equal speed up the grade (or on flat land where the divisor is 0).   Or, HPT x 12 / %G = Speed.

So, the answer to your question would be it probably can't be done.   The weight to power ratio would mean running so many motors that they would weigh more than they can start or pull.

An educated guess, within the parameters above, it can't be done, except perhaps moving an impossibly small load., on an impracticle scale.

Addendum:  Torque also applies to the prime mover, or movers in this case.  Although the horsepower of automobile engines may be equal, they will lack the torque to turn the massive alternator when under load, at sufficient rpm to produce the power needed to supply the traction motors.  In addition, conventional diesel prime movers reach full power, with maximum torque, at somewhere around 915 RPM.  Most automotive motors don't hit the bottom end of their power curve until 1500 RPM or higher, wih the power band extending to perhaps 5000 rpm.  They wouldn't last long.

Even though NHRA nitro burning engines can develop 7,000 HP, they can only do it for five seconds, however.  Tractors in pulling competition run as many as five, blown alcohol, big block motors, and still 25 tons 300 feet is the best they can do.  I can't think of an empty freight car that weighs as few as 25 tons, but they may exist.

Assuming the question refers to a train in the conventional sense, it won't work.  If it were so, a number of less expensive automobile engines would quickly replace today's common prime movers, that drink diesel at a rate of 170 gallons per hour when in full throttle (run 8).

So, I still say it won't work on any kind of meaningful scale.

Answer 5

Electro motive devices such as a train could run on one auto motor turning a generator. But for speed and hills it takes lots of kilowatts of energy to power the electric motors under the locomotive. And lots of diesel fuel and crankcase oil. One locomotive could power a small town's electrial grid.

Answer 6

A diesel locomotive can put out 3200 horsepower. If you do the arithmetic then you would need 20 car engine with 160 horsepower to get the same power. (Of course fitting them all in and coordinating their contributions to driving the train would make that impractical.)

Answer 7

If you could connect the car engines to the main alternator you would probably need about 10 engines to power one locomotive...that is assuming a 250 horsepower car engine...that would be good to pull about 20 box cars..

Answer 8

5