968 THE COLLIERY GUARDIAN. November 6, 1914. several weeks without cessation. Moreover, the drivers and firemen of such engines are usually less skilled. Industrial locomotives should therefore be constructed of the very best material, and the design and workman- ship throughout should be of the highest class, in order to make them reliable and able to withstand every kind of shock to which they may be subjected. An engine that has to be continually laid up for repairs is not a cheap one, as a substitute has to be hired or a demur- rage account faced. Firms accustomed to build home and foreign main line engines, being conversant with the highest class specifications, and their workmanship having to satisfy the most stringent inspection, will, in the event of their also specialising in the construction of the industrial locomotive, be without doubt the more reliable builders of the latter. Such firms buy only from the best sub- contractors, and generally specify that the materials of construction throughout are to be to the British Standard Specifications No. 24 (revised 1911) for tests and requirements. As regards workmanship, no firm can do good and indifferent in the same works, and if this were attempted, then main line orders would be with- drawn. Should such firms also undertake repairing and rebuilding work,’they are in an especially advantageous position to construct an ideal industrial locomotive, having then the experience of competing firms added to their own. Type. The class of engine almost universally employed is the plain four-wheels-coupled, possessing, as it does, the Table XI.—Showing . Smallest Curves which may be NEGOTIATED BY 0—6—0 Type ENGINES WITH VARIOUS Wheel Bases and Wheel Diameters on the Stan- dard Gauge of 4 ft. 81 in. £o Usual A Radius of curves (in feet). t All Centre Centre X Dia. of Wheel pair pair o S Q wheels. has". LUICK , i • fla^es’ flanges. flange- 14 ss. In. Ft. in. Ft. in. 12 x 18 ... 3 Of ... 8 6 .. 18i ... 120 . 75 13 x 18 ... 3 1 ... 9 0 . 200 ... 133 . 80 14 x 20 ... 3 4 ... 10 0 .. 245 ... lt>3 . 9 > 14 x 22 ... 3 6 ... 10 6 .. 265 ... 176 . 95 15 « 22 ... 3 8 ... 11 0 .. 288 ... 192 . . 104 16 x 24 ... 3 10 ... 12 0 342 ... 228 . . 120 17 x 26 ... 4 L ... 13 0 .. 385 ... 256 . . 130 18 x 26 4 3. 14 6 490 ... 326 . . 150 Note.—These curves do not take into account the widen- ing of the i ails on curves, and may therefore be considered quite safe. Nor is side play, which is sometimes given to the trailing axle boxes, allowed for. Tables I. and II. show the curves which can be nego- tiated by foifr- and six-wheels-coupled engines having various wheel bases and wheel diameters. The four- wheels-coupled locomotive is manufactured with cylin- ders up to 16 in. diameter by 24 in. stroke, weighing about 37 tons, and representing an engine of enormous power considering the short wheel base of 6 ft. 6 in.; while plain six-wheels-coupled locomotives are con- structed up. to sizes with cylinders 18 in. by 26 in., and weighing about 56 tons. in practice for this class of engine when combined with the resistances to traction stated later :— qk X s x mp) T— 85 D where T = tractive power at rail in pounds. d = diameter of cylinders in inches. s = stroke of pistons in inches. mp = mean effective pressure in cylinders (75 per cent, is the maximum cut off usually employed). D = diameter of driving wheels in inches. From the diagram fig. 1 may be deduced the maxi- mum tractive power for engines having various sizes of cylinders and wheels. For other working pressures multiply by the constants stated. T x V The rail h.p. = —— where V is the speed in miles per hour. The resistance to traction can be obtained from the diagram fig. 2, which shows the resistance due to grade + 12 lb. per ton for frictional resistance, this being a good average allowance for the trucks and wagons usually dealt with. If, however, curves are to be nego- tiated this resistance of 12 lb. per ton should be aug- mented by 50 per cent. Fig. 3 shows the relative tractive force and gross load in tons on various grades. Boiler Power.—The boiler should be suitably propor- tioned to supply the quantity of steam demanded by the cylinders when developing their maximum continuous Fig. 5.—Hedley's "Puffing Billy.” Fig. 6.—4-W.C. Saddle tank Engine with Open Cab. ] I -Wii Fig. 7.—4-W.C. Saddle-tank Engine with Closed Cab. Fig. 8.—4-W.C. Saddle-tank Engine, Cab Provided with Backplate. advantage of being able to negotiate very sharp curves, which is of primary importance in shipyards, factories, etc., but in the ease of coal companies having a long run on a private line, or for use on a temporary rail- way laid down for contractor’s purposes, the six-wheels- coupled locomotive may be necessary. This type, of course, runs more smoothly, there being not the same tendency to lurch or dip as in the case of the former class. Or again, in the event of the rails being of too light a nature, and the curves permitting of the longer wheelbase, the six-wheels-coupled may be deemed advisable. It is considered a safe rule in the majority of cases to divide the weight of rail per yard in pounds by five, the quotient indicating, in tons, the axle load permissible. Table I.—Showing Smallest Curves which may be NEGOTIATED BY 0—4—0 Type Engines WITH VARIOUS Wheel Bases and Wheel Diameters dard Gauge of 4 ft. 8| in. on the Stan- Cylinders. Usual Radius a of Dia. x stroke. Dia. of Wheel wheels. base. curves. In. Ft. in. Ft. in. Ft. 10 x 15 2 10 5 0 34 12 x 15 2 10 6 0 44 12 x 18 3 Of ... 5 6 40 13 x 19 3 4 5 6 41 14 x 22 3 6 5 6 42 15 x 22 3 8 6 0 47 16 x 24 3 10 6 6 53 Note.—These curves do not take into account the widen- ing of the rails on curves, and may therefore be considered quite safe. Standard Gacgk or 4 feet 8| inches. Cylinders. Dis. ... 10" 12" IS- 14” 15” 16" 17" 18" Width over all T 4J" 7' 6J' 7' 9’ 7 IT 8' 1J" 8' V 8' 6" 8’ 9' Fig. 4. Showing the usual width of Oven Cylinders for Engines with various diameters of Cylinders with- out decreasing the length of Crank Pins and Journals, &c. Capability. The capacity of a locomotive for doing useful work in an economical manner depends upon the suitable pro- portioning of the following factors :—Mechanical power, boiler power, and adhesion. Mechanical power, or the work developed in the cylinders transmitted to the wheels, and exerted by the latter on the rails. This is generally termed the trac- tive power, and must be sufficient to haul the required loads up the steepest gradient and around the sharpest curves at a reasonable speed. There are numerous formulee used for determining the tractive effort of'a locomotive, but the following gives very reliable results work. This is especially important in the case of, say, colliery engines working for a long period on a lengthy gradient. On the other hand, for a locomotive doing intermittent shunting in works, where the grades are generally short, it is advisable that the boiler should not be . too large, as there is a loss of economy when the engine is standing or doing only light duty. Boilers for this class of engine generally have the following proportions :— Total heating surface _ grate area Firebox heating surface -s grate area Total heating surface , Firebox heating surface These ratios are, of course, averages, and may be varied to suit special conditions. With boilers proportioned somewhat as above the total heating surface can be converted into terms of H.P. approximately by the formula— H.P. = HS' * 13 = '46 H.S. 28 13 representing the evaporative power per sq. ft. of heating surface per hour, and 28 the weight of steam required per H.P. hour. Adhesion.—The weight on the wheels must be ample to prevent slipping under the worst climatic conditions. The ratio of adhesion to tractive power for 4 w.c. engines is generally about 5 to 1 with tanks and bunkers full, which ratio is, however, reduced to about 4-25 to 1