Journey from Steam Locomotive to Bullet Train

TRAIN HISTORY

Trains played very important role not only during industrial revolution but also is very important in today's fast growing world. From steam locomotive to bullet,maglev trains we have seen so many changes that have not only reduced the time to reach destination but also more safe,reliable and comfortable.It is very important to know the working of the trains with new technology and how effectively they use technology to overcome various hurdles.

After the wagon's were invented,they were frequently used as horse-wagon to transport goods and people for long distance. But the real application came when the steam locomotives were invented which can drive tonnes of load from one place to another.

There were many invention carried out on steam engines before they were utilized in trains.Mostly they were used in cotton mills,water-pumps etc which were of low capacity because of low pressure generation.

MODELED BY AMAL NAMBIAR(toy train)

MODELED BY AMAL NAMBIAR(toy train)

 'James Watt', a Scottish inventor & mechanical engineer was responsible for improvements in steam engine of Thomas Newcomen, hitherto used to pump water out of mines. Watt developed a reciprocating engine capable of powering a wheel & patented in 1784. After more improvements it was used in most part of the world for transportation through trains.

Maglev Train

More advancement was made after the introduction of diesel and electric locomotives. They are cleaner,more efficient and requires less maintenance compared to steam locomotive. World's first electric tram line opened in Lichterfelde near Berlin,Germany built by Wernet von Siemens.But now the recent advances in train are bullet train, Maglev train which have speed more than take-off speed of an aircraft.

TGV-France

The maximum operating speed for bullet train is 320 km/hr (200mph). Tests run have reached 443 km/hr (275mph) for conventional rail in 1996 and upto a world record 603km/hr (375mph) for maglev in April 2015. Also TGV( Train a Grande Vitesse-High speed train) of France has a record speed of 574.3 km/hr (352.7mph) on 3 April 2007.

But the first fastest train was developed by Japan - Bullet train.

BULLET TRAIN:

A normal train can't sustain the stresses the bullet train undergoes and due to this Japan engineers had to redesign the whole concept keeping in mind 'speed, comfort,safety'.

The first part that needed to be redesigned, was the wheels. Well they are obviously round in shape but the important part is surface that makes contact with rails. If the shape is not accordingly, everything can possibly go wrong.

Train wheels are not perfectly flat as you might think. It is little bit conical with track as as shown in figure above. This angle has being kept to keep the wheel in contact to track during cornering while a flat wheel will just derail or run out of rail. Even with flanges on side that guides the wheel,using it in flat wheels will wear out very soon. Hence use of conical shape wheels solved the problem in conventional trains. The optimum amount of angle will provide the wheels to be in contact with the track. But this angle will cause 'hunting' when the speed is increased beyond limit.

 Hunting is unusual and unwanted oscillation caused due to cone angle as shown below.

Hunting due to slope, source: wikipedia

Bullet train wheel slope

So, they cannot use conical shaped wheel in bullet train as used in conventional trains because bullet train run at speed of nearly 200MPH. By the use of flatter wheels this problem can be solved but again they create a problem during turning. Hence they are not made conical as conventional but little flatter i.e half of the conventional slope angle. Each wheel is precision-ed machined and accurately build to avoid hunting and derailment. Obviously the coil spring also plays an important role in stabilizing the hunting even in lateral direction.

Next important thing to be kept in mind was speed which indeed is available from power available. The power can be increased in two ways 1)By increasing current 2)By increasing voltage.
But by increasing current it produces large amount of heat as per joule's law which can burn up the wire. In-fact if we pass high current, very thick wire is required which is not possible because cables are spread thousand's of miles, due to which it becomes very expensive. So, increasing current is ruled out. So, the only choice is voltage step-up. Bullet train needs nearly 25,000 volt for its functioning. Thus, the cable are supplied with such high voltage. But there is one problem?

Plasma created due to gap

The panto graph which keeps contact with the wire if looses contact with it, the power is lost. But this is not the main problem. The main problem is that if there is a gap between two conductors carrying very high voltage then the air between them can be turned into plasma, 'the fourth state' of matter which is very hot, about 10,000 °C . Hence it is required to maintain proper contact with the wire or arc will be produced which will be catastrophic. 

Pantograph in action

Due to this problem, panto-graph's are computerized to maintain the contact with the help of  hydraulic power. Moreover the cable lines are not in straight line but in zigzag way such that wear doesn't occur only in one part of panto graph, but is evenly distributed.Simple but very effective solution.

Now comes the question of power generation through voltage source. Generally conventional train consist of single locomotive that pulls the wagon. So the power generated is only by the locomotive but not at wagon's wheel. But this cannot be used in bullet train which runs at 200MPH. So, their is separate motor for each unit of bullet train called as multiple unit system which makes it possible to run at such high speeds. Each motor drives two wheels so, approximately it is 112 wheel drive. And this helped to keep traction and quickly gain speed in bullet train after starting.

Accident of commuter train during cornering

Next challenge was to keep up the same speed during cornering. Centrifugal force,that forces train outwards can prove to be deadly at high speed cornering. In 2005 a commuter train took a bend too fast and flew off the track. In this accident 107 people lost their lives. So, in order to reduce the centrifugal force the rails are inclined inwards as shown in below image. But this works well for slow trains. 

The bullet train have to lean in direction of cornering without reducing the speed just as in bike racing they lean during cornering to keep same speed as shown in below image.

 This is done precisely by computerized airbags under each carriage.

Leaning of bullet train due to Airbag

Now the major problem before engineers that only Japan faces is frequent earthquake.Japan is exposed to nearly 900 quakes a year,and in march 2011 an earthquake measuring 9 on Richter scale hit Japan causing death of thousands of people and destruction to properties. The country is located in earthquake prone zone and in such situation the train has to be stopped before it can get into disaster. For this the train drivers should know that earthquake is coming before they enter that zone. But no superhuman is born to tell that and seismic instrument are not that sensitive to detect quake from the epicenter far away. So,how do they detect quake?

Actually the earthquake consist of two waves 1) Primary wave or P-wave 2)Secondary wave or S- wave. S- waves are slower than P-waves but cause much destruction. The key to advance warning was to detect the faster P-waves. But to detect P-waves we need very sensitive seismometer.  Hence electromagnetic seismometer is used to detect P-waves. When this powerful sensitive seismometer detect P-waves the power is switched off & any train in danger zone automatically brakes and stops. For vehicles of stopping distance of nearly 2 miles every second counts and this advance warning system proved very advantageous for bullet train. The March 2011 earthquake destroyed stations,tunnels and bridges up and down the bullet train network but crucially not a single bullet train was affected in earthquake as the earthquake warning system brought them to halt,in some cases 15 seconds earlier than the rail was damaged by quake.

Hence engineers worked lot harder to develop a train that is fast,comfortable, reliable and safer than most of the trains in world.