That steam is raised in the boiler of a locomotive by the combustion of coal, whence it passes into the cylinders to do its work I knew from my boyhood days. Being a student of science I was acquainted one degree further with the principle of the piston valve whose job it is to admit steam alternately on each side of the piston as it moves within the cylinder. Be that as it may, a close look at a locomotive at work always gives rise to an uneasy feeling, an overwhelming sense of ignorance of the inner working of the fire breathing creature Stephenson gave to the world.
Today was a remarkable day for I have quite unexpectedly received a most interesting tutorial in steam locomotive operation from Mr Lal, the shunting engine driver. After a fruitless search for an absorbing book at the Wheeler’s bookstall, I proceeded to Platform No 4 which is my usual hangout when at the station. The object that held my attention today was a tank loco, Class WM 2-6-4, busy shunting carriages. The engine heaved and puffed and after a labour of nearly half an hour came to a stand a little beyond the platform ramp. The driver got off and strolled into the station presumably for a cup of tea. He was a young man, thirty something with a face that seemed not too severe, so I walked up to him and introduced myself. It is quite possible that he had seen me several times on this side of the station, for not once did he give me a questioning glance.
After social preliminaries were over, I put before him the matter that was on my mind all along. I have often wondered how it comes about that on starting, an engine lets out clouds of steam from the cylinders, and after a while ceases to do so, thereafter expelling the whole volume of steam through the chimney in rhythmic puffs. Why does steam first issue forth from the cylinders, and why the changeover a few moments later?
We had our cups of tea and moved out into the yard where the engine stood. There, as we bent over together, Mr Lal showed me a stem that actuated two valves at the lower edge of the cylinder. “These are known as cylinder drain cocks,” Lal explained looking up at me. “When actuated from the cab, the drain cocks open and let out steam from the cylinder.”
It seems to be all a big fuss but drain cocks on a locomotive serve a vitally important purpose, I was told. When starting from rest, the cylinders of an engine are usually cold, so boiler steam, when admitted, tends to condense into water. The accumulation of water in a locomotive cylinder presents a grave danger, for trapped water can form an obstruction as impregnable as steel to the movement of the piston. Thus to prevent a piston from smashing into a barrier of trapped water, the drain cocks are opened at the start of the run, expelling any water that may have condensed together with the steam as it blows out. After a few minutes of this preliminary, the cocks are shut, the steam being now wholly discharged through the chimney.
And as though to make sure I understood the operation, Mr Lal invited me into the cab. The faceplate of a locomotive boiler has an impressive array of gadgets most of which make no sense to the layman. Lal quickly pulled a lever and began to open the regulator. Great clouds of steam engulf the engine at the front, and we begin to roll out amid a deafening roar. A short while later Mr Lal deactivates the cylinder drain cocks. Leaning out of the footplate, I found that the discharge of steam had ceased, which was now being expelled in pleasant little puffs from the chimney above.
The demonstration over, Mr Lal actuated a lever. “This ,” he tells me, “is the ejector.” Seeing that I am a young man interested in technical detail he is eager to explain the various parts that go to make up a steam engine.
“The ejector creates the vacuum necessary for operating the train’s brakes,” he tells me. “There are three components of prime importance here,” he emphasized. “The ejector that creates the vacuum, the injector that forces water into the boiler against the pressure of the steam, and the lubricator which supplies a mixture of steam and mineral oil to lubricate the steam chests and cylinders.”
On regular passenger and goods trains the services of a fireman are indispensable, but shunting work seems to be more a relaxed job. A shunting engine working in a passenger yard is rarely required to remain in operation throughout. “Now that we have shunted the Hissar Passenger to the Carriage & Wagon examination line, there is little more to do till noon when I am called upon to shunt a sectional carriage that will be attached to the Deluxe,” he explains.
The shunting engine works only spasmodically and Mr Lal has enough time on hand to shovel coal himself. At 5 O’ clock he signs off and hands over charge to a colleague. Towards evening the engine will back at work shunting in the Ferozepur Passenger and other slow trains bound for nearby districts.