How does a train work?

Question

How does a train work?

Answer 1

A broad question, indeed.  An answer must touch on a little history as well.

If you are going to operate a train you will need three basic building blocks; motive power, rolling stock and road bed.  Lets take the latter first.

Roadbed usually consists of two or more steel rails held in place by cross ties (sleepers in the UK) made of wood or concrete.  These are laid on top of ballast, the familiar rocks under the ties.  Ballast helps hold the rail in place, as well as providing for drainage, but also allow a certain amount of give, vertically, to help lessen the forces where wheel meets rail.  The next time you see a train pass, look at the rail and notice what happens each time a car's truck passes over.  In North America, as well as other places, "standard" gauge is 4'81/2", which is the inside dimension between the rails.

The wheels of the equipment have a flange on the inside of the wheel so it can follow the track, but that is not what keeps it on the track.  It is gravity that keeps the equipment on top of the rail as its tremendous weight keeps the flanges from climbing the rail.  As long as vertical force is less than lateral force "L/V" the equipment will stay on the rail.  If lateral force exceeds vertical force, equipment will derail on a curve by either coming off to the inside, called "string lining", when the train is in draft (stretched out slack), or to the outside, or "high side", as a result of jackknifing when the train is in buff, where the slack is bunched.

Now that we have roadbed, we need rolling stock, in the form of passenger or freight equipment.  Not much to say here, except to touch on how they are coupled together and the brake system each has.

Each car is coupled to another vis what is known as the "automatic coupler", invented by William Janey, long ago.  Prior to that time the cars were coupled by "link and pin".  Cars had horizontal pockets on each end, into which a brakeman had to insert the link by hand as the cars were moving, and drop a pin therough a hole on the top of the pocket.  No one could claim to be a brakeman without at least one or two missing fingers.

Today's cars incorporate "draft gear".  This is comprised of the "cutting lever", used to uncouple the cars, the knuckle, the drawbar, end sill and center sill.  Many of today's cars have end of car cushioning devices to lessen the mechanical shock as slack action propagates through the train.  These can be a spring loaded coupler pocket or a sliding center sill.

The most important piece of equipment on a car is the brake system and rigging.  An air line, commonly called the "brake pipe" or "train line", runs the length of the train and is coupled between the cars with a rubber hose equipped with a "glad hand" at the end.  These are metal devices that allow the hose to be coupled by hand but automatically separate when uncoupled.

Air reservoirs on each car, the auxilliary and emergency, are charged with air from the engines' main air reservoir.  Freight cars are charged to 90 psi while passenger trains operate at 110psi.  The brakes are applied when the engineer operates the automatic brake valve to allow air to escape from the brake pipe.  Valves on each car sense this drop in pressure which causes them to change position, opening a port from the auxilliary reservoir which puts air into the brake cylinder.  The brake rigging then applies the brake shoes to the wheels.  This system was envisioned and put into practice by George Westinghouse with the Westinghouse Air Brake Co.

Now we need power.  Lot's of it.  The first were literally powered by horse power, pulling trolleys or carts along behind them.  Then the steam engine came into play.

Simply put, these were boilers on top of drivers.  They used wood, coal or oil as fuel.  The earlist were very simple engines, more powerful than a horse but far less formidable than those that were around at the last of steam, in the US.  In many areas, in particular in African countries, portions of China and South America as well, steam engines still ply the rails in regular service.

There were sub-groups here, including single expansion reciprocating, compound, cross-compound, saturated steam, superheated steam, as well as the Shay type, Heisler type and Climax type, the latter being gear driven, as opposed to the familiar side rod design.

Engines with diesel prime movers fell into the categories of diesel, diesel electric and diesel hydraulic, with the diesel electric at the top of the heap.

The prime mover turns an alternator (there is a generator but it is an auxilliary power supply for low voltage needs, such as battery recharging, lights) which generates power for the traction motors which are axel hung and turn the drive wheels through a ring and pinion type gear box.  There is also a "companion" alternator which supplies excitation for the main alternator and runs cooling fans.

Most of the locomotives out there today are still equipped with DC (direct current) traction motors.  The alternators in these engines have banks of rectifiers to convert the electricity into DC before feeding it to the traction motors.  Newer engines are AC and much more efficient.

Diesel electric locomotives also have an engineer's best friend, dynamic brake.  Essentially this reverses the supply process, turning the traction motors into generators, which provides retarding effort.  The electricity they generate is dissipated through a grid, as heat, the very same way a toaster works.  Further electricity is used to run the fans that keep the grid to a cooler temperature.

Electric traction is primarily in the eastern portion of the US, though the Great Northern had electrified railway in the west as well, necessary to navigate the over 7 mile long Cascade Tunnel.

Power is supplied by an overhead conductor, suspended by a catenary, and the pantograph on top of the engine picks up the power.  Power is also applied via a "third rail".  As its name implies, it is a third rail near the two running rails that allows the engine to pick up the electricity.  Some systems, such as the London Underground, actually use a forth rail as well.

Diesel hydraulic power made a very brief appearance in the US.  These engines, manufactured by the German company Krause-Maffei, were diesel powered, but equipped with a hydraulic transmission.  They didn't make the grade as the drive lines continued to break under the punishment of the mountainous regions where they were put into service.

ALCO made a gas-turbine electric locomotive in the 60s, know as the "Century".  Extremely powerful and extremely loud as well.  They were primarily relegated to service in more desolate areas, such as the desert south west.  Expensive to maintain, they didn't last long.

There are other types of railroad in other areas that are cog driven, cable assisted and funicular, but are usually light duty or for tourism purposes.

Trains also are very efficient at killing people.  No, they don't come looking for you or lurk in the shadows until ready to pounce.  But the right of way is their sandbox, and if you put any part of yourself in close proximity they'll be more than happy to dismember or kill you.

That's how trains work.....................

Answer 2

On diesel trains there are diesel engines running electric motors (generators). I've been told that this is very efficient. limates transmissions. If you want to run reverse just run the motor in reverse.

Answer 3

Derrr, 'as a big injin that pulls trucks.

Answer 4

(deep resigned sigh...!)

Which sort of 'train'?

(sigh again)

Sash.

Answer 5

Heat creates pressure, which moves pistons, which move the wheels. Alternatively, electric trains move the train with motors which are supplied electricity through the tracks.

Answer 6

with the aid of a Train driver

Answer 7

Steam, electric or diesel electric?

Answer 8

On a steam locomotive, a fire in the firebox heats water to create steam. This steam is channelled through tubes to the steam dome, where the engineer regulates the amount of steam that will go into the cylinders (sort of like what a gas pedal in a car does). This steam is channelled to the cylinders, where it pushes the connecting rods, which turn the wheels. The used steam is then shot out of the smokestack with the exhaust from the fire.

On a diesel locomotive, diesel fuel powers a 12- or 16-cylinder engine. The energy is transformed into electricity in the generator. The electricity is then sent to the tractive motors (located near the wheels), powering the locomotive.

An electric locomotive works alot like a diesel, except that it receives electricity from an overhead catenary system or a third rail. This electricity is then sent to the traction motors, powering the loco. Since no engine is needed inside of the locomotive, the engine is lighter, allowing for faster starts and stops. This makes it ideal for commuter service and high-speed passeger trains.

Answer 9

It doesn't usually does it?

Answer 10

A real one works by having a locomotive pulling or pushing cars down two guide rails called a track. The wheels have inside flanges that keep the cars on the track. A locomotive is a motorized car. Electric motors are mounted down by the wheel set, known as a truck and drives the wheels through a set of gears. A simple answer to a very broad question.

Answer 11

A simple question that will require a detailed answer.... hoghead should be along soon and give you a great answer.....

Answer 12

with it's engine

Answer 13

Do you mean choo choo trains,mine has a string that you pull and the choo choo follows,there is a new one now that you paint the tracks and it follows that,i am 54 years of age,and i am going to the pub shortly,whoo,whoo,chuff,chuff chuff