Engineering Wonders of the World
Volume I

214 ENGINEERING WONDERS OF THE WORLD. At the present day two main types are gen- erally used: (1.) The “Fairlie,” or double- boiler type. This has two sets of coupled wheels, both mounted on pivoted frames, so that very sharp curves can be taken with ease. Each set has its own cylinders. The two sets are separated by a considerable dis- tance, thus distributing the weight, a fact which allows short bridges to be of com- paratively light construction. The design is practically two locomotives in one, each of moderate dimensions and weight, giving the total effect of a large and powerful locomotive without the disadvantages of unwieldy size, great weight, and lack of flexibility. (2.) The single-boiler type, which may be subdivided into (a) the Meyer, with two pivoted frames, each having two cylinders taking steam direct from the boiler. This has been largely super- seded by (&) the Mallet type. In this case the engines are compound, and the rear set of coupled wheels, carried by the main frames, are driven by the high-pressure cylinders, whereas the fronf set, fitted in a pivoted swing- ing frame, are actuated by the low-pressure cylinders. This system is very suitable for large dimensions, and has been developed widely in Europe and America. Fig 46.—LARGE “shay” geared locomotive for the SOUTHERN RAILWAY (U.S.A.). Au interesting form of articulated engine is shown above. The “ Shay ” is primarily designed for working on roughly laid tracks in timber or lumber districts, under conditions which would derail an ordinary locomotive before it had travelled half a mile. The design usually includes three cylinders arranged vertically at the side of the boiler to drive a longitudinal shaft. This shaft is in sections provided with universal joints, and carries bevel pinion wheels gearing with bevel teeth on the faces of the wheels, all of which are used for driving. The illustration shows four bogies, two under the engine and two under the tender, so that sixteen driving wheels are available. This apparently awkward and lop-sided arrangement is compensated by placing the boiler somewhat oft the centre line. Many large and interesting Shay engines are used by the important American and Canadian railways, and in some cases weigh upwards of 100 tons. Fig. 47.— MEYER TYPE LOCOMOTIVE FOR NARROW GAUGE GREEK RAILWAY. Two engine bogies and one boiler. The steam from the rear engine exhausts through the chimney ris- ing above the coal bunker. Built by Andrew Barclay and Co., Limited, of Kil- marnock.