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How a Steam Loco works

Since the inception of the railways, a normal train comprised of a powered vehicle that pulled (or pushed) the train, and other vehicles that had no power of their own but were normally pulled (or sometimes pushed) by the powered vehicle.  This powered vehicle is called a locomotive, or a loco, in short. This was the norm and even today is the norm in our country.  However, with the multiple unit trains and train sets increasing, the latter may well replace a large number of locomotive hauled trains in the future. Be that as it may, all long distance trains in India, except the Vande Bharat Express, are locomotive hauled and have been so hauled since the start of rail transportation in India.

The earliest locos were powered by steam, later followed by electricity and finally by diesel fuel. It would not be out of place to mention that well before powered locomotives became standard for all railways, rail transportation already existed using animal power for movement.  Both, horses and cattle have been used.  Most of these early railways were in mines or from the mine to the nearest road or waterway.  The Gaekwad State Railway around what is now Vadodara used oxen on the mainline in the 1860s before steam locomotives were introduced.

Locomotives started very modestly. One of the earliest models erected was by Britain’s Richard Trevithick, a Cornishman.  This little engine weighed about 5 tons compared to later behemoths that weighed well over 100 tons.  The most well-known of the early locomotives was the Rocket.  This is the locomotive that won the famous Rainhill Trials and powered the Manchester-Liverpool Railway that started operations in 1929.

It is not the intention to give a detailed history of steam locomotives.  Suffice to say that for more than half the period that the railways have been in operation, the locos used were steam. In our country, barring some electrification around Bombay (now Mumbai) and a short stretch from Madras (now Chennai) in the 1920s, all trains were steam loco hauled.  Diesel and electric locos made inroads only in the latter half of the 1950s and it was only in 1995 that the last Broad Gauge steam locomotive was removed from service.  Meter Gauge steam on the main lines disappeared in 1998.  Today, there is no steam locomotive operating in the country except a few heritage runs and on two of the hill railways, Darjeeling Himalayan Railway (Narrow Gauge) and the Nilgiri Mountain Railway (Meter Gauge), where some of the services are still on steam.  The latter runs are retained as heritage and tourist attractions. There are attempts to introduce steam locos on the Matheran Railway as well by using the B class locos that are being used on the Darjeeling Himalayan Railway.

Thus, of the more than 16 decades since the railways have been in existence in our country, they chugged along with steam power for about 75% of the time. Let us have a broad look at how the steam locomotive works.

Working of Steam Loco

To produce steam, you have a boiler (see diagram 1). The boiler requires a fuel that will burn and heat the water to convert it to steam.  While there have been wood-fired and oil-fired locomotives around the world, in India, we have used coal almost exclusively.  We do have some oil-fired locomotives working on the Nilgiri Railway now, but on the main lines, we used only coal. The coal was shovelled by a fireman into the firebox where it burnt and produced hot gases that went through the flue tubes and out as exhaust from the smoke box through the chimney. The firebox and the tubes were surrounded by water which got heated and finally converted to steam.  This steam was sent through superheater tubes inside the flue tubes to get superheated. The latter was then piped to the steam dome from where is went to the cylinders that caused a piston to move to and fro due to the steam pressure.  The reciprocating motion of the piston was converted to rotary movement of the wheels that caused the loco to move forward.

Apart from the boiler, the steam loco had a tender at its rear. The tender was the place where you stored the water and the coal that the loco needed. Between the tender and the boiler you had the area where the driver and the fireman did their work. This area is normally referred to as the footplate (see diagram 2).

The reciprocating movement of the piston was transferred to the wheels through a connecting rod.  The connecting rod, fixed to an eccentric pin on the wheel, then turned the wheel. Other wheels were coupled to this driving wheel through coupling rods so that you could have four to five sets of wheels coupled thus.  There were other wheels on the loco in front and behind these driving wheels. 

The steam loco driver or loco pilot had to be tough and skilled.  The footplate was open to the elements and gave little protection from the hot winds in summer and the correspondingly cold blasts in winter.  The latter was worse as while you got frozen on one side by the external air, the heat of the firebox scorched you on the other side.  At the same time, the pilot had to ensure adequate steam pressure, sufficient water level in the boiler and a host of other things.  The fireman’s job was physically exhausting as he normally manually shovelled coal into the firebox.  Some of the Western countries used mechanical stokers but we did not do so in India.

One interesting feature was that in the steam loco days, one loco pilot or driver, as he was called then, was assigned to one locomotive on a more or less permanent basis.  Owing to this, there was a strong bond between the loco and its permanent pilot, so much so that the latter lavished a lot of love and care on the former.  In many cases, the pilot took leave when his loco was sent to the workshop for heavy repairs.  If you visit any railway colony, you will hear tales of the drivers of yore, who, it is claimed, loved their locos more than their wives.

All said and done, it is sad to find only electric and diesel locos hauling a train.  With fire in its belly and visible moving parts, the steam loco was like a living being and had a romance of its own that the current locos just cannot match. Train sets and multiple unit trains have even less romance. Of course, ultimately the needs of the day made the steam loco obsolete so that barring a few that are still breathing fire and smoke, you now see them only on pedestals in museums or in front of railway stations and other rail establishments.   

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