How does a Train Stop?

Question

This isn't for me, it's for my brother. He wants to know how trains stop for his class.

Answer 1

a very simple answer:

the creation of friction(heat) and the dissipation of the resultant heat is what stops them.

hoghead has covered it really well, but i  have a correction to make though.

"The hand brake. As its name implies, they are operated by hand, turning a wheel or ratcheting a crank to put the brake shoes against the wheel. It applies the brake on all of the wheels of a car"

handbrakes do not always act on all the wheels of the car.  some cars have one hand brake that may act on all of the wheels, some may have one hand brake that acts on 6 wheels some may have 1 handbrakes that acts on 4 wheels (of as many as 12 or 16) some have 2 brakes that act on 8 out of 12 wheels .  suffice it to say;  i am nit-picking and do not mean to diminish his answer in any way..

there are many different car/handbrake configurations in use today

Answer 2

One of two ways:

1.  Pressure is applied to the wheels in motion.  Usually this is some sort of carbon or steel based shoe that causes friction on the moving wheels causing them to slow.  Look at your bicycle tire brake and notice the brake pads how they squeeze the wheel and cause it to slow.  A train works the same way.

2.  The train hits something big.

Option one is much preferred if you are a passenger.

Answer 3

The above posters only got half of the answer right..   They mentioned the airbrake, but did not mention dynamic brakes.

Currently, there are two different of types of brakes for trains:

The first kind is the regular air brakes that was invented by George Westinghouse back in the late 19th Century.  Compressed air are used to press brake shoes against the wheels of the railroad cars, causing the train to come to a stop.  Sometimes sand is sprayed onto the rails to help give the wheels some grip (the sanders are located on the locomotives).

The second kind of brakes are called dynamic brakes.  These work by using the traction motors on the locomotives as electrical generators to slow down the train.  Generating electricity with the traction motors converts the kinetic energy of the train into electrical energy, slowing it down.  The electricity generated from the dynamic braking are either dissipated as heat (using heating grids) or stored into batteries if the locomotive is a hybrid (like the GG20 Green Goat switcher), or used to power passenger car electrical circuits (like in the General Electric P32AC-DM dual-mode Genesis locomotives used by Amtrak and Metro-North).

Dynamic brakes are used to save wear on the friction airbrakes.

Wikipedia article on dynamic brakes:  http://en.wikipedia.org/wiki/Dynamic_bra...

Hope this helps.

Answer 4

Wow!

Everyone is all over the place on this one...

It's all very entertaining.

Addendum:   Point well taken Petero.  I am remiss.  Please accept my apologies and find the following for the edification of all:

The air brake system on a train is first charged with air, 90 psi for freight operation, 110psi for passenger.

The 'main air reservoirs' on the locomotives are supplied by a three cylinder, two stage air compressor.  Nominal pressure is 140psi

The air travels from the main reservoir into the 'brake pipe' via the 'regulating valve' on the locomotive.  With the brake valve handle in release, air flows through the brake pipe charging the 'auxiliary' and 'emergency' air reservoirs on the cars.  This is accomplished by the control valve on each car.

When wanting to apply the brakes on the train, a reduction of 5 to 7psi is made in the 'equalizing reservoir' on the engine, found within the air box.  This is called 'minimum reduction,' and it is done automatically on the 26L brake schedule, by moving the brake valve handle to the first detent.  On older brake schedules, such as the 24M and 24RL, this reduction in the equalizing reservoir air pressure is made by moving the valve handle to the application zone, and then moved back to the 'lap' position, which engages the pressure maintaining feature.  This is automatic on the 26L schedule.  "Desk Top" type brake schedules function identically, but the positions are labeled.

The pressure in the brake pipe will drop correspondingly to the drop in the equalizing reservoir.  When the pressure in the brake pipe drops, it causes the control valve on each car to move into the application position, which changes the configuration of the ports and passages to allow air from the auxiliary reservoir into the brake cylinder on each car.  This initiates 'quick service', which puts 10psi into the brake cylinder.  Then, a system of rods and linkage applies the brake shoes to the wheels to reduce speed or stop.

Propagation time, the time it takes for the reduction in brake pipe pressure to run the length of the train is, rounded off, 500 feet per second.  So, If your train is 8,000 feet long, it will take sixteen seconds before the rear car ever sees the brake pipe reduction.  This is one of the reasons trains take so long to slow or stop.  If you're traveling at 60mph, you've gone 1/4 mile before the brake shoes even make contact with all the wheels.  Other factors in stopping distance include grade, Tons Per Axel of Dynamic Brake (TPAD), Tons per axel of Operative Brake (TPOB) and speed.  

The rate of propagation of an emergency application is, rounded off, 1,000 feet per second.

Of course, the air has to be put back when the brakes are released.  Re-charge time is 1 minute for each 12 cars in the train.

Dynamic brake as mentioned above doesn’t reverse anything, except for the process.  There are four basic types of dynamic brakes.  Flat, Taper, Standard and Extended Range (Extended range is nullified when stopping by the IPS [independent pressure switch] to avoid sliding the engine wheels).  The IPS is usually set near 15psi.  The features are usually combined, such as flat-extended range or taper-standard, etc.  There is a fifth kind, called the Field Loop, but this is only found on first generation dynamic brake equipped locomotives.

In dynamic brake, the traction motors are essentially turned into generators, which provides retarding effort.  The electricity generated in diesel electric locomotives when in dynamic is dissipated as heat through the dynamic brake grids.  Additional electricity is used up to run the grid cooling fans, dissipating more of it.  This is why the pitch of the characteristic 'whine' of the dynamic, created by the fans, changes as the engineer makes changes with the dynamic brake controller.

There is also braking available through the engine brakes, also referred to as independent brake or 'jam.'  At times, for slack control, you will want to apply the brakes on the train only, while keeping the engine brake released.  The usual valve found is the 6SL.  The ‘SL’ denotes self lapping.  This is done by depressing the valve handle, in an action referred to as bailing off.  This brake can also be applied independently of the train brakes.  J1 valves will put a maximum of 45psi into the BC Equalizing pipe.  These are found on older locomotives with cast iron brake shoes.  Most road engines have the J1.6 valve, which will develop 72 psi in the engine brake cylinders at full application.

There is 26psi of available air before the system equalizes.  At equalization,  you’ll have 64psi in the equalizing reservoir, the brake pipe and the brake cylinders on each car.  Since the air-brake system works on being able to create a differential in air pressure, you have no more brakes.  The only remaining option is to place the rain into emergency application.  Here, the control valves on each car allow the air in the emergency reservoir on each car to flow into the brake cylinders.  This produces 13 more psi in the brake cylinder on each car.  

It will also open the PC (Pneumatic Control) valve on the locomotives, which will nullify dynamic brake or power, as well as engaging the A-1 Charging Cut-off Pilot valve, that will keep the brakes from releasing until the engineer recovers the PC.  

To recover the PC, the throttle or dynamic control levers are closed and the automatic brake valve handle is moved to the 'suppression' postion for a minimum of 1 mintue 20 seconds to recover from a 'penalty' application of the brakes, as the result of an allertor time-out or locomotive overspeed.  (Suppression is found on the quadrant on the hump just past the 'full service' detent and before the 'handle off' position.)

To recover the PC from from an emergency application of the brakes, or to iniate an emergency application, the handle is moved to the emergency position, the last on the quadrant, past handle off.

Passenger trains operate a bit differently.  Here, the brakes can be backed off if too much is applied.  This is called 'graduated release.'  Not available on freight equipment.  There, applied or released are your only two options.  In addition, passenger locomotives are usually equipped with blended brake, where the air and dynamic are controlled together with the automatic brake valve handle.

As far as reversing the traction motors (what was Air Brake Rule 13), not only will it do damage, it is useless, unless on a lite engine moving at walking speed.



The last braking system is the simplest.  The hand brake.  As its name implies, they are operated by hand, turning a wheel or ratcheting a crank to put the brake shoes against the wheel.  It applies the brake on all of the wheels of a car, but only 1 wheel of 1 axel on a locomotive.

There is a bit more to it, but, 'thumbnail,' there ya go...

If ya wanna learn the air, ask a HOGHEAD.

Answer 5

Brakes !!

Answer 6

Breaks!!!! break shoes press up against the foot of the wheel ( part where wheel meets rail ) and the train stops. All rail cars and locomotives have em

Answer 7

It can take a quarter of a mile to break a train. they do not stop on a dime. the enginerr is qualified on the line and knows how to break the train so it stops at the stations.

Answer 8

Trains stop two ways...

Westinghouse designed air brakes.   As long as the air lines are intact and the pressure is at the specified pressure,  the brakes stay off.   When they want the train to stop,  they reduce the pressure and the brakes come on.   If an air line was cut or come disconnected,  the drop in air pressure would also apply the brakes.  

The diesel electric train engines can also be used to brake a train.  They stop the flow of electricity to the electric drive motors,  turning them into resistance brakes.   They usually use that for long down hill runs such as some of the runs in the west.   That saves wear and tear on the air brakes.  

They may also dump sand in front of the wheels to help increase resistance when they brake and to help keep the wheels from just locking up and sliding along the rail.

Answer 9

They have air brakes.LOL no really read this,it may help. http://www.southdevonrailway.org/Brake-C...

Answer 10

All trains have a continuous braking system controlled from the driving cab and the guard's van.

The brakes may be either vacuum operated or compressed air and are fail-safe, that is, they need a vacuum or a supply of compressed air to keep them off. If the vacuum or compressed air is released, the brakes come on and the train will stop. Earlier trains had shoe brakes which acted on the wheel treads but most trains today have disc brakes which act on the radius of the wheel itself.

All the carriages on the train are connected by hoses which link the brakes together, hence the term, 'continuous braking'.

If the train should divide en route by accident, the connection will be broken and the train will stop.

The UK government passed a law that all passenger trains should be fitted with continuous brakes after a particularly nasty accident in 1889 in Armagh, Northern Ireland where a passenger train broke in two going downhill. The front half of the train came to a stop and the back half ran into it, killing and injuring many of the passengers.

Freight trains continued to be loose-coupled for many decades after that, the only brakes when in motion being on the engine and brake van. To apply brakes on the wagons the train had to stop and the brakes were applied by hand. However, 'fitted' (i.e. continuously braked) freight trains gradually came into use and nowadays all freight trains have continuous brakes.

Steam locomotives were usually fitted with a steam brake for the loco itself, and a compressed air or vacuum brake for the train. Compressed air brakes were often known as Westinghouse brakes after the company that made them and an engine thus fitted would carry its air pump (2 cylinders one above the other) and air reservoir (a long, horizontal cylinder) prominently near the front. Steam locos in Europe were sometimes fitted with 'counter-pressure braking' where the steam supply to the cylinders was reversed, causing the engine to slow down and stop, but this was not used in Britain.

The 09 series of diesel shunters in use with various operators on Network Rail have both air and vacuum brakes fitted so they can work with any kind of rolling stock.

Another safety measure introduced on British trains was the communication cord, for use by a passenger in an emergency. Pulling the cord alerts the driver and makes a partial application of the brakes.

Diesel and electric trains in Britain have a 'dead man's handle' or treadle - basically a lever or pedal which the driver has to keep pressed while the train is in motion. If the pressure is released - e.g. if the driver is suddenly taken ill - the brakes some on.

European trains have an 'attendance button' which the driver must press every 30 seconds. Fail to do so and the brakes are applied.

British trains are also fitted with the Automatic Warning System or AWS (now being replaced by Automatic Train Protection or ATP) in which a driver receives a warning if the train passes a caution signal (yellow signal, warning that the next signal is red) and if he does not apply the brakes they come on automatically.

The ancestor of these was the Automatic Train Control, introduced by the Great Western Railway in 1906. Various updated versions of this are used in railway systems all over the world.

Answer 11

There are four ways to stop a train.

1. Dynamic Brake - reverses the electrical current within the traction motors.

2. Independent Brake - only applies brakes on the locomotives.

3. Automatic Brake - applies the brakes on the complete train - if the independent is not bailed (a release movement) the automatic also applies to the locomotives, but will cause the wheels to skid.

4. Plugging the traction motors - moving the reverser (the key we use to move the train backwards or forwards) from forward to reverse.

5. To stop the train in an emergency, you apply full independent, move the automatic to emergency position, centre the reverser, and move the throttle to off (I would be inclined to move to full dynamic).

I have not had to use emergency yet and touch wood. I'll never be in that position.

Number four is not used to stop a train in everyday use - but for an extreme emergency - it causes a lot of damage!!!

Independent and automatic, drop the air pressure - which causes the brakes to apply. So to release the brakes - air pressure must rise.

A traction motor is what drives the wheels, so the train can move along the track.

Distance to stop the train depends on various factors.

Weight of the train, track condition, weather and how much you apply the brakes. But they do not stop on a dime!!!!

If everyone is all over the place 'HOGHEAD', how come you did not answer?

Answer 12

There are different types of braeks:

!. the show which presses against the wheel

2. a break similar to the one of a car (those in Porsches and Mercedes).

3. electro magnetic breaks. Kind of a magnet is activated and lowered slightly above the rail

4. If t is an electrified line, the motors of the engine (or those distributed in the boogies of the high speed trains) act as dynamos and by this break the train and feed electricity back into the electric lines.