Sherlock Holmes and the Chinese Junk Affair and Other Stories (19 page)

How simple it all seemed when explained by Holmes, yet how baffling had it all seemed only twenty-four hours ago.

The train began to snake and slow down as it approached the outer network of track leading into the station. There was a squealing from the carriage wheels as they protested when taking some of the sharp curves.

‘Now there’s a puzzle for you to solve, Watson.’

‘Puzzle... where?’ I looked about me.

‘Under your feet.’

I looked at the floor. ‘You have the better of me, Holmes.’

The train came to a halt as it stood by a signal, awaiting the track ahead to clear.

Holmes replied, ‘On a straight piece of rail track the wheels on each side of the axle revolve at the same speed, the revolutions equal. However, when the track curves, one wheel has to revolve faster than the other.’

I must have looked a little blank so Holmes decided to elucidate.

‘Think of a boy and his train set. He sets up the track in a circle. Now, the outer rail of the circle is larger than the inner rail of the circle... correct?’

I agreed, but perplexed as to what it was all leading up to.

‘So,’ continued Holmes, ‘the wheels on the outside rail then have to revolve faster than the wheels on the inside rail because there is more rail to traverse.’

I agreed again, but could still not comprehend where the puzzle was, and said so.

‘I don’t see any puzzle, Holmes. The wheels on the axle, just like those on a cab or coach, revolve at different speeds to compensate for this.’

To emphasise the grasp of my understanding I continued, ‘When a cab turns to the left, the left-hand-side wheel revolves more slowly. Likewise, when the cab turns to the right, the right-hand wheel revolves more slowly. They revolve independently of each other on the axle.’

‘That is absolutely correct, Watson, only there is a problem... the wheels on all railway rolling stock are fixed to the axle; rigid, solid, welded together. One wheel cannot revolve faster or slower than its partner on the same axle.

‘When running on a straight piece of track, there is no problem, each wheel turning at the same revolutions as the other. The problem arises when the track begins to curve; whether to the left or right, the problem remains the same.

‘As we see with the train set, the wheel on the outer rail has to revolve faster than the one on the inner rail... it’s the law of physics... so how does rolling-stock cope with this problem when negotiating a curve, without twisting and wrecking the axle?’

I gave him a long look, not realising until then that railway rolling-stock did have their wheels fixed rigid to the axle. Any further thoughts on the subject were interrupted by the train jerking and beginning to move forward again. The familiar sound of clickety clack, clickety clack was heard as the wheels passed over points and crossovers, before the train glided to a halt inside the station.

Doors were flung open, porters dashed forward with wheelbarrows to assist with luggage; the whole familiar bustle and noise, so very different from the staid quiet country station we had entrained from. We waited in turn to give up our tickets and then were swept along again with the outpouring mass of humanity, like us, eager to leave the station.

Observing the demand for cabs, Holmes suggested we walk back to Baker Street as it would be just the thing to bring back the circulation to our legs, after our enforced inactivity.

We walked along the pavement by the side of a row of cabbies. The drivers struggling to assist the passengers enter their cabs, others were heaving and tugging at heavy luggage, intent upon securing it onto the roof-racks. Trade was roaring. As one cab left the rank and left a space, another filled it, the horse knowing exactly what was expected of it from years of experience.

I describe this scene because one particular cab was turning round as it was facing the wrong direction it was to go. We paused and watched the wheel nearest the pavement revolve several times, whilst the other one made perhaps half a turn as the cab completed its one hundred and eighty degree turn.

It was a perfect demonstration of the physical science of free-turning wheels on the same axle and, likewise, it revealed the problem involved with railway rolling stock; the wheels being fixed and unable to turn independently of each other created, so it would appear, enormous stresses on the wheels and axles, even when traversing the slightest curve.

We walked on, my brows knitted in deep thought. Obviously the problem, puzzle, call it what you may, had been solved long ago by pioneering railway engineers, yet it is never given a moment’s thought by those who travel daily on the train. It was a first-class conundrum indeed.

I had the feeling that Holmes had a trace of a smirk on his face; however, I was determined to discover for myself the puzzle of the fixed railway wheels... but it would have to be all in good time. I have not the best mind when it comes to scientific matters.

We turned into Baker Street to be met with the familiar sights; street hawkers, flower sellers, newspaper boys shouting the latest headlines, all rubbing shoulders with the home-going workers.

Perhaps the countryside was quieter, but I was glad to be back and part of the London scene. I am sure Holmes was too, but sentiment was not one of his strongest points.

I closed the street door behind us and followed Holmes along the passageway and up the stairs to our rooms, but my mind was already back to trying to solve the railway wheel puzzle. Could it... no, no, perhaps not... but how about... not that either... ? Holmes had certainly set off a hare for me to chase.

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