From the Civil Engineer and Architect's Journal. [Note in The Railway Times — George P. Landow]
With the progress of the locomotive engine, it has, like other machines of extensive use, attained that period when its economy becomes of the greatest importance. Influenced by such considerations, Mr. Robert Stephenson has directed his attention to a less consumption of fuel, and to effecting a more simple arrangement of the machinery, both of which points have been well managed in his new engine now running on the York and North Midland Railway. Economy in the consumption of fuel has been obtained, by adding considerably to the length of the tubes, without increasing the distance between the front and back axles of the engine; consequently the space occupied by the engine upon the bearing is precisely the same, therefore no alterations are requisite in the turnplates, or other arrangements made for the accommodation of the ordinary locomotive. The machinery is simplified by placing the axles of all the wheels under the cylindrical portion of the boiler, the axle of the front wheels being placed close to the smoke-box, and the axles of the hind wheels close to the fore-most end of the fire-box, instead of the back partThis arrangement allows the axle of the driving wheels to be placed in the centre of the other two axles, or at such intermediate distance as may be found the most suitable for the moving parts. The alteration in the construction of the boiler and tubing gives a heating surface of 800 superficial feet, whereas in the ordinary engine it rarely exceeds 450 feet, being for the new plan a superiority of fully 350 feet. Such is the effect produced by this addition, that the temperature of the air escaping in the chimneyscarcely exceeds the temperature of the water in the boiler; a circumstance which has a further beneficial effect beyond the economy of fuel, for it has been found, by increasing the extent of heating surface, and employing usefully the whole of the heat generated in the fire, that a less violent draught of air is required; the consequence is that very few hot ashes are thrown out of the chimney; this peculiarity is quite remarkable in the engine now running. A few days since, a journey of 90 miles was performed by this engine, during which no ashes were thrown out of the top of the chimney, and at the same time the accumulation in the smokebox was very trifling, not exceeding a fourth of the usual quantity. As the tendency to eject ashes from the chimney is dependent upon the speed, it is necessary to state, that the speed was never below 20 miles per hour, generally exceeded 30, and for several miles a speed of 48 miles per hour was uniformly attained, with five loaded coaches.
The consumption of fuel during the above experiment was 19.2 lb. per mile, with a load of eight coaches over half the distance (45 miles), and five coaches over the remaining half. This consumption includes the whole of the fuel used in lighting the fire and raising the steam.
We may truly say, that we have never witnessed an instance where speed and economy were combined to the same extent; indeed, under no circumstances have we heard of the consumption of fuel being reduced to so low a figure. It must, however, be borne in mind, that this result is from a single experiment, and that we must not be deluded by isolated trials; but we are glad to hear that on the line where the engine is now working, the Company have ordered an accurate record of the performance, and quantity of fuel consumed during each trip, which we hope will be made public. Mr. Stephenson has introduced tubes of wrought iron, instead of brass or copper, in order that the increased heating surface might be obtained without a corresponding augmentation in the price of the engine. This he has not adopted without making several experiments. During the last twelve months he has had several boilers working under his own eye with iron tubes, for the special purpose of determining how far he could recommend them for general adoption. The result has been all that he could desire ; and it is owing in some degree to this, that he has introduced them with greater confidence. Having now described the modification in the boiler, we shall proceed to point out Mr. Stephenson's alterations in the mechanical arrangement.
In the ordinary engines, the mechanism for working the slide valves is very liable to derangement, and considerable wear and tear. This part of the engine he has so far simplified, as to require only a simple connection between the eccentrics and slide valves, thus doing away with a considerable number of moving parts, which have hitherto given rise to more casualties than any other part of the ordinary engine. This is attained by placing the slide valves vertically on the sides of the cylinders, instead of on the top, as heretofore, so that the direction of the sliding motion of the valves, and the central line of the valve rods, will intersect the central line of the main axle, at the point where the eccentric is placed. In this case, the eccentric rods are connected immediately to the prolongation of the valve rods, without the usual intermediate levers and weigh bars; besides, the slide valves of both cylinders are placed in one steam chest between the cylinders.
Another improvement is that effected in the working of the feed pumps : it consists in connecting the pump rods to the coccutrics used for reversing [388/389] he engine. By this arrangement the velocity of the moving part of the pump is greatly diminished, by which is secured greater regularity of action. n addition to what we have already described, there are several minor alterations, which we cannot fully explain without giving detailed and elaborate drawings.
The following are the principal dimensions of the engine now working on the York and North Midland Railway —
|Diameter of cylinder||14 inches.|
|Length of stroke||20|
|Diameter of driving wheels.||5 1/2 feet.|
|Diameter of small wheels||3 feet|
|There are 150 tubes, giving a heating surface of||765 feet|
|[Plus the] Copper fire-box, with a heating surface of||30 feet|
|Total heating surface||795 feet.|
|Length of boiler, including fire and smokeboxes||17 feet.|
|Weight of the engine in working order||15 tons.|
“Railway Offences and Offenders.” Railway Times. 5 (2 April 1842): 388-89. Hathi Trust online version of a copy in the University of Michigan Library. Web. 2 September 2018.
Last modified 2 September 2018