“On the 20th of January, 1863, Mr. Fell took out his first patent, and on the 16th December, of the same year, his second, under the modest title of ‘improvements in locomotive engines and railway carriages.’ In neither of these patents did Mr. Fell attempt to appropriate to himself the invention of the centre rail, but simply the means, both ingenious and practical, by which he has succeeded in applying the principle of additional adhesion.”
“Independent of the energy, perseverance, and straightforward practical sense, of which he has given proof, in his long train of trials and experiments, Mr. Fell’s principal merit, in our opinion, is that he has understood, what theory entirely justifies, that locomotives with additional adhesion are only applicable to steep gradients and slow speed, because such engines are able to develop powerful means of traction, without heavy additions to their weight.”
Early in 1863, Mr. Fell instituted experiments on a length of line of 800 yards, laid out on his plan, upon the Cromford and High Peak Railway, near Whaley-Bridge. The gauge was 3 feet 7½ inches, 180 yards of the line were straight with a gradient of 1 in 13 (406 feet in the mile); 150 yards with a gradient of 1 in 12 (440 feet in the mile); with curves of two chains and a-half each. The centre rail was raised seven and a-half inches above the surface of the two ordinary rails, so as to be acted upon by the two horizontal wheels of the engine. During the experiments, the first engine of the kind ever constructed, and necessarily, from want of experience, unsatisfactory in many of its details, working with a pressure of 120 lbs. to the square inch, was always able to convey a load of twenty-four tons up the incline. The maximum it succeeded in taking was thirty tons. Its dimensions were as follows: diameter of cylinder, 12 inches; length of stroke, 18 inches; four wheels coupled, diameter 2 feet 3 inches; axles, 5 feet 3 inches apart. The weight of the engine fully loaded with coke and water was sixteen tons. When the pressure was only brought to bear upon the vertical wheels, the engine could not take more than a weight of seven tons up the incline, but when the horizontal wheels acted combinedly with the perpendicular, she took up twenty-four tons on the same day, and under circumstances precisely similar in every respect, except as regards the action of the horizontal wheels upon the centre rail.
These experiments were considered so satisfactory, that it was decided, with the permission of the French Government, and for its information, that they should be repeated upon a more extended scale upon the Mont Cenis, with the condition made by Mr. Fell, that if the system were found to be practicable, the authorities should grant the concession of a portion of the roadway for a line to be laid down across the French division of the mountain on the same terms as had already been agreed to by the Italian Government for the Italian portion.
The experimental line was laid down between Lanslebourg and the summit. It commenced at the height of 5,305 feet above sea level, and terminated at the elevation of 5,820 feet. Its length was two kilometres all but forty-four yards, or an English mile and a quarter. Gauge, 3 feet 7½ inches. Its mean gradient was 1 in 13, the maximum was 1 in 12; it had two curves of 44 yards each, and others, the most favourable of which was 125 yards. It will thus be seen that the line was constructed in a manner, both as regards gradients and curves, to subject the system to the severest tests. The experiments, which were conducted in the presence of commissioners from England, France, Italy, Austria and Russia, lasted from the end of February until the end of May 1865, and it is a remarkable fact that the adhesion was found during the period of snow better than could be expected in summer, for when snow was swept off the rails, it left them dry, and under favourable conditions; whereas, summer dust combined with moisture, would render them comparatively greasy and slippery. Captain Tyler, who was present at all the experiments on the part of the British Government, calls special attention to this curious fact in his report.
Two engines were employed in the trials, the first that which had been used on the High-Peak Railway experiments, and the second an engine built specially for the service of the Mont Cenis Railway. This latter was the engine principally employed, No. 1 being chiefly used to supply the place of No. 2, when any trifling derangement in its machinery required attention. It is intended that No. 2 shall be used on the completion of the line over the pass, and it is the engine by which the trial trip was accomplished on the memorable 26th of August, 1867. When empty its weight is 13 tons, when loaded with coke and water 17 tons 2 cwt. The horizontal wheels and the machinery connected with them weigh 2¾ tons. The boiler is 8 feet 4 inches long, 3 feet 2 inches diameter, and contains 158 tubes of 1½ inches exterior diameter. Heating surface 600 feet. The cylinders, two in number, 15 inches diameter, with 16 inches stroke, act at one and the same time upon the two systems of wheels, four horizontal and four perpendicular. Each system of wheels consists of four coupled, diameter of each 2 feet 3 inches. The space between the centres of each pair of perpendicular wheels is 6 feet 10 inches, that between the horizontal wheels 2 feet 4 inches; maximum pressure of steam in the boiler 120 lbs. per square inch; effective pressure upon the piston 75 lbs. This engine was a great improvement upon its predecessor. With engine No. 1, Captain Tyler, R.E., from whose Report to the Board of Trade the foregoing particulars are taken, says that during the space of two days he descended and remounted the experimental line six times. The train behind it consisted of three waggons, with a total gross weight of 16 tons. The average of his experiments was as follows:—The first ascent was made in 8 minutes 15 seconds, with a loss of 14 lbs. of steam, and of 5½ inches in the gauge glass; the mean pressure of the steam varied from 92 to 125 lbs. per square inch. The speed in each of the experiments was greater, with the same load, than is proposed for the express trains. The mean speed resulting from the figures above stated, was at the rate of 13 kilometres, 300 metres per hour (8 English miles), instead of 12 kilometres (7½ English miles), the highest speed specified in the programme submitted to the French Government for this part of the line. The weather was fine and calm, the external rails were in very good condition; but the centre rail, as well as the horizontal wheels were greasy, and consequently in a very unfavourable condition for adhesion.