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MR - 0-4-4 Tank Engine (1876)
Midland Railway 0-4-4 Tank Engine (1876)
We give this week a two-page engraving, together with other views on the present and opposite pages, of one of a class of powerful tank locomotives constructed from the designs of Mr. Samuel W. Johnson, for working heavy local passenger traffic on the Midland Railway. The engine now illustrated may be considered to be a development of the type introduced by Mr. Johnson on the Great Eastern Railway, while he was the locomotive superintendent of that line - a type which has done excellent service. As will be seen from our engravings, the engine has two pairs of coupled wheels 5 ft. 6in. in diameter, the axles of these wheels being situated under the barrel of the boiler at a distance of 8 ft. apart from centre to centre. The trailing end of the engine is carried on one of Mr. William Adams* bogies, this bogie having two pairs of 3 ft. wheels placed at 5 ft. centres, and the centre of the bogie being 11 ft. 3 in. in the rear of the centre of the driving axle. The total wheel base is thus 22 ft. 9 in., or measuring from centre of leading axle to centre of bogie, 19 ft. 3 in. The cylinders are inside, and are 17 in. in diameter, while the stroke is 24 in.
*We have said that the trailing end of the engine is carried on one of Mr. Adams’ bogies. The leading features of this bogie, as many of our readers are aware, consist, first, in the centre bearing being taken on a large India-rubber pad, and, secondly, in the bogie frame being not only free to turn upon the bogie centre, but also to shift laterally to an extent controlled by springs acting horizontally. In the case of the engine under notice, the main frames are reduced in depth behind the firebox, their thickness, however, being at the same time increased from 1 in. to 1 ½ in., and they are tied together just above the bogie centre by a pair of strong transverse stays which not only transmit the load to the bogie, but also take the pull of the trailing draw-bar. The bottom flange (as we may call it)of the box girder formed by the transverse stays just mentioned, consists of a plate 1 in. thick and 2 ft. 7 in. wide, and to this plate is bolted a casting of the form shown in Figs 1 and 6. Between this casting and another sliding on the bogie frame is placed an India-rubber ring 2 ft. in diameter and 4 in. thick, this ring forming an elastic centre bearing for the bogie and leaving the latter free to cant in any direction as regards the engine frame. A thin brass dish is interposed between the India-rubber ring and the lower casting, the interposition of this brass dish allowing any necessary circular movement to take place between the India-rubber ring and the lower casting. The upper casting, it will be noticed, has a centre pin 6 in. in diameter formed on it, this pin entering into a correspondingly bored hole in the lower casting. This latter casting rests upon steel rubbing pieces fixed to the central transverse stays of the bogie frame, a part of the casting also fitting between the angle irons forming this transverse stay. The lower casting is capable of sliding laterally 2 in. each way, but its lateral movement is controlled by the India-rubber springs arranged as shown on the plan, Fig. 2, and transverse section Fig. 5. The axle-boxes of the bogie wheels are connected on each side of the engine by a compensating beam, through which the load is transmitted from the ends of a steel spring. This spring is attached at its centre to a link, which passes down through the transverse frame of the bogie and a thick India-rubber ring below, as show in Fig. 5. This arrangement of springs and India-rubber pads gives, as may be anticipated, very easy riding. we have frequently expressed a favourable opinion of Mr. Adams’ bogie, believing, as we do, that it is the best arrangement of its kind yet brought out, and this being so, we are glad to learn that it has found its way into very extensive use, not only in this country, but also on lines abroad.