LOCOMOTIVE See also:

• POWER [WILLIAM GRATTAN] TYRONE (1797-1841)

. . =RV (2) where Ti, T2, T3, &c. are the torques on the axles whose respective angular velocities are wl,See also:

• W2(P — R1)

Methods of Applying Locomotive Power.—By locomotive power is to be understood the See also:

• PROVISION (Lat. provisio)

Assuming the wheels to roll along the rail without slipping, this couple will be equivalent to the couple formed by the equal opposite and parallel forces, F1 acting in the direction shown, from the axle-box on to the frame, and Fr=µB, acting along the rail. The torque corresponding to this couple is Fl X ID = luWID, and hence follows the fundamental relation, 2T=aFID=µWID, or if W now represents the weight supported by the axle, F will be the tractive force exerted on the frame by the two axle-boxes to propel the vehicle, and the more convenient relation is established, value of the tractive force is required than this provides for, namely from 4 to 5 tons, the driving-wheels are coupled to one or more pairs of heavily loaded wheels, forming a class of what are called " coupled engines " in contradistinction to the " single engine " with a single pair of loaded driving-wheels. Mechanical energy may be See also:

• DEVELOPED

Ultimately the question resolves itself into one of commercial practicability. For suburban See also:

• TRAFFIC

A " perfect engine " receiving and rejecting steam at the sametemperatures as the actual engine of the locomotive, would develop about twice this power, say 1400 I.H.P. This figure represents the ideal but unattainable See also:

• STANDARD
• STANDARD, BATTLE OF THE

Thus an engine working at maximum power may be used to haul a relatively See also:

• LIGHT

§ 5. Vehicle Resistance and Draw-See also:

• BAR
• BAR (0. Fr. barre, Late Lat. barra, origin unknown)
• BAR, CONFEDERATION OF
• BAR, FRANCOIS DE (1538-1606)
• BAR, THE

Inst. C.E. (1901), vol. 147. Aspinall's results are expressed by the See also:

• FORMULA
• FORMULA (Lat. diminutive of forma, shape, pattern, &c., especially used of rules of judicial procedure)

The resistance found from the above expressions includes the components 1, 2 and 4 of § 4. The resistance caused by the wind is very variable, and in extreme cases may See also:

• DOUBLE
• DOUBLE (from the Mid. Eng. duble, the form which gives the present pronunciation, through the Old Er. duble, from Lat. duplus, twice as much)

H. See also:

• SMITH
• SMITH, ADAM (1723–1790)
• SMITH, ALEXANDER (183o-1867)
• SMITH, ANDREW JACKSON (1815-1897)
• SMITH, CHARLES EMORY (1842–1908)
• SMITH, CHARLES FERGUSON (1807–1862)
• SMITH, CHARLOTTE (1749-1806)
• SMITH, COLVIN (1795—1875)
• SMITH, EDMUND KIRBY (1824-1893)
• SMITH, G
• SMITH, GEORGE (1789-1846)
• SMITH, GEORGE (184o-1876)
• SMITH, GEORGE ADAM (1856- )
• SMITH, GERRIT (1797–1874)
• SMITH, GOLDWIN (1823-191o)
• SMITH, HENRY BOYNTON (1815-1877)
• SMITH, HENRY JOHN STEPHEN (1826-1883)
• SMITH, HENRY PRESERVED (1847– )
• SMITH, JAMES (1775–1839)
• SMITH, JOHN (1579-1631)
• SMITH, JOHN RAPHAEL (1752–1812)
• SMITH, JOSEPH, JR
• SMITH, MORGAN LEWIS (1822–1874)
• SMITH, RICHARD BAIRD (1818-1861)
• SMITH, ROBERT (1689-1768)
• SMITH, SIR HENRY GEORGE WAKELYN
• SMITH, SIR THOMAS (1513-1577)
• SMITH, SIR WILLIAM (1813-1893)
• SMITH, SIR WILLIAM SIDNEY (1764-1840)
• SMITH, SYDNEY (1771-1845)
• SMITH, THOMAS SOUTHWOOD (1788-1861)
• SMITH, WILLIAM (1769-1839)
• SMITH, WILLIAM (c. 1730-1819)
• SMITH, WILLIAM (fl. 1596)
• SMITH, WILLIAM FARRAR (1824—1903)
• SMITH, WILLIAM HENRY (1808—1872)
• SMITH, WILLIAM HENRY (1825—1891)
• SMITH, WILLIAM ROBERTSON (1846-'894)

17. Thus let an engine and tender weighing 8o tons haul vehicles weighing 200 tons at a uniform speed on the level of 40 M. per hour. As given by the Barbier curves in fig. 17, the engine resistance at 40 M. per hour is 20 lb per ton, and the vehicle resistance 8.5 lb per ton at the same speed. Hence Engine resistance, Rs= 8o X20 = 'Goo lb Vehicle resistance, RD=200X8.5=1700 „ Train resistance, R = 3300 The speed, 40 M. per hour, is equal to 58.6 ft. per second; therefore the rate of working in foot-pounds per second is 3300 X58-6, from which I.H.P.=(3300X58.6)/550=354. This is the horse-power, therefore, which must be developed in the cylinders to maintain the train in motion at a uniform speed of 40 M. per hour on a level straight road with the values of the resistances assumed. § 8. Rate at which work is done against a gradient.—Gradients are measured either by stating the number of feet horizontally, G say, in which the vertical rise is 1 ft., or by the vertical rise in 100 ft. measured horizontally expressed as a percentage, or by the number of feet rising vertically in a mile. Thus a gradient of 1 in 200 is the same as a See also:

• HALF

(18) Assuming the data of the previous See also:

• SECTION
• SECTION (Lat. sectio, cutting, secare, to cut)

7o Too Curves showing VA/oh A Esselte iteelstarm is tbs. per too Speed In See also:

• NILES

" Experiments on Steam oilers, See also:

• DON
• DON (anc. Tanais)

The best way of deducing r, is to select portions of the dynamometer record where the speed is See also:

• CONSTANT, BENJAMIN (1845-1902)

lb the resistance of a badly laid track; and show how both the potential energy and kinetic energy of the train are continually changing: the first from a change In vertical position due to the gradients, the second from changes in speed. These consideratipns also Indicate what a difficult See also:

• MATTER

The first one of the group was made on the boiler fixed in the locomotive yard at See also:

• STRATFORD
• STRATFORD, JOHN DE (d. 1348)

English practice where a spark-arrester is put in it usually takes the form of a See also:

• WIRE (A.S. wir, a wire; cf. Swed. vire, to twist, M.H.G. wiere, a gold ornament, Lat. viriae, armlets, ultimately from the root wi, to twist, bind)

Distribution of steam is effected by a slide See also:

• VALVE (Lat. valva, a leaf of a double or folding door, allied to volvere, to roll, as of a door on its hinges)

Secondly, it must be able to maintain the train at a given speed against the total resistances of the level or up a gradient of given' inclination. These conditions are to a certain extent mutually antagonistic, since an engine designed to satisfy either condition independently of the other would be a different engine from that designed to make the best See also:

• COMPROMISE (pronounced compromize; through Fr. from Lat. compromittere)

Fig. 20 shows the standard proportions recommended by the See also:

• COMMITTEE (from commute, an Anglo-Fr. past participle of commettre, Lat. committere, to entrust; the modern Fr. equivalent comite is derived from the Eng.)

E. Dalby (London, 1906). The plotting of the torque curve is laborious, but the average torque acting, which is all that is required for the purposes of this article, can be found quite simply, thus: Let p be the mean effective pressure acting in one cylinder, a, the area of the cylinder, and 1, the stroke. Then the work done during one revolution of the crank is 2pla per cylinder. Assuming that the mean pressure in the other cylinder is also p, the total work done per revolution is 4pla. If T is the mean torque, the work done on the crank-axle per revolution is 2~rT. Hence assuming the mechanical efficiency of the engine to be e, and substitutingEd' for the area a, 4 2TT = 4plae = plird2e, T = §pd2le. But from § i, T=§DF; therefore F = p&le/D (25) F in this expression is twice the average magnitude of the equal and opposite forces constituting the couple for one driving-wheel illustrated in fig. 16, one force of which acts to propel the train whilst the other is the value of the tangential frictional resistance between the wheel and the rail. This force F must not exceed the value µW or slipping will take See also:

• PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

If p is the mean pressure at any speed the total tractive force which the engine is exerting is given by equation (25) above. The value of a is variable, but is between •7 and •8, and for approximate calculations may be taken equal to unity. In the following examples the value will be assumed unity. These relations may be illustrated by an example. Let an engine have two cylinders each 19 in. diameter and 26 in. stroke. Let the boiler pressure be 175 lb per square inch. Taking 85% of this, the maximum mean effective pressure would be 149 lb per square inch. Further, let the diameter of the driving-wheels be 6 ft. 3 in. Then the tractive force is, from (25), (149 X 192 X 2.166)/6-25 =18,600lb = 8.3 tons. Assuming that the frictional resistance at the rails is given by § the weight on the wheels, the total weight on the driving-wheels necessary to secure sufficient adhesion to prevent slipping must be at least 8.3 X5 = 41.5 tons. This would be distributed between three coupled axles giving an average of 1.38 tons per axle, though the distribution might not in practice be uniform, a larger proportion of the weight falling on the driving-axle.

If the starting resistance of the whole train be estimated at 16 lb per ton, this engine would be able to start 1.163 tons on the level, or about 400 tons on a gradient of 1 in 75, both these figures including the weight of the engine and tender, which would be about See also:

• LOO (formerly called " Lanterloo," Fr. lanturlu, the refrain of a popular 17th-century song)

With exception-ally See also:

• BAD, BCD

Effici- lb per b/D power. envy. sq. in. 4 o 128 0.073 Mean Deduced from a ~? 205 0.075 about data given by 222 0.080 128 but Professor Goss a 399 0.088 throttled. (Trans. Am. H Soc. Mech. Eng. vol. 14). -.~ mean 1 129 0.057 0.815 0.047 mean Deduced from about Kennedy and 120 See also:

• DONKIN, SIR RUFANE SHAW (1773-1841)

Inst. C.E. vol. 125). 4 520 0.084 0.52 0.044 140 Deduced from 5 692 0.083 0.65 0.054 175 Smith's experi- 6 558 0'074 0.69 0.051 175 merits (Prot. 7 603 o.o86 0.63 0.054 175 Inst. Mech. 8 570• 0.081 0.64 0.052 16o Eng. October 1898). It is instructive to inquire into the limiting efficiency of an engine consistent with the conditions under which it is working, because in no case can the efficiency of a steam-engine exceed a certain value which depends upon the temperatures at which so that RAILWAYS It receives and rejects heat. Thus a standard of comparison for every individual engine may be obtained with which to compare its actual performance. The standard of comparison generally adopted for this purpose is obtained by calculating the efficiency of an engine working according to the See also:

• RANKINE, WILLIAM JOHN MACQUORN (182o-1872)

The back pressure is supposed to be uniform, and there is no See also:

• COMPRESSION

22 by the curve AB. The curve was drawn by calculating the thermal efficiency from the above expression for various values of the initial temperature, keeping the final temperature constant at 673°, and then plotting these efficiencies against the corresponding values of the gauge pressures. The actual thermal efficiencies observed in some of the cases cited in Table XXI. are plotted on the diagram, the reference See also:

• NUMBERS, BOOK OF
• NUMBERS, PARTITION OF

For further information regarding the standard engine of comparison see the article STEAM ENGINE and also the " Report of the Committee on the Thermal Efficiency of Steam Engines," Proc. Inst. C.E. (1898). § 16. Piston Speed.—The expression for the indicated horse-power may be written I.H.P. =pav/55o (27) where v is the average piston speed in feet per second. For a stated value of the boiler pressure and the cut-off the mean pressure p is a function of the piston speed v. For the few cases where data are available—data, however, belonging to engines representing standard practice in their construction and in the design of cylinders and steam ports and passages—the See also:

• LAW
• LAW (0. Eng. lagu, M. Eng. lawe; from an old Teutonic root lag, " lie," what lies fixed or evenly; cf. Lat. lex, Fr. loi)
• LAW, JOHN (1671—1729)
• LAW, WILLIAM (1686-1761)

Inst. C.E., 1905-6; vol. 164.) Substituting this value of p in (27) See also:

• LAP

Compound working permits of a greater range of expansion than is possible with a See also:

• SIMPLE

It was of the same type as Mallet's engine, and was made by simply bushing one cylinder of an ordinary two-cylinder simple engine, the bushed cylinder being the high-pressure and. the other cylinder the low-pressure cylinder. Webb evolved the type of- three-cylinder compound with which his name is 'associated in 1882. t87 ovblo feeh Indicate, diagr0m 0orresponding to 1 /b. of steam for the Rankin Engine of Comparison when initial pm& is 199lbs sq. Inch absolute, and exhaust prised. v.14.71bs sq. Inch absolute 940. WIMP= =EMI 111 Gaure ressure Etrff s,an , r er I. the j~o/um ~1 ;~ - ]--~erperimen .odic• ted b the cross _- - 0.20 o» 09e e,1 0M 6.15 OA. o•ls 0.12 0.10 0.09 0.00 0-07 o- 0-00 0-04 0-03 0-02 001 126 100 ,e0 200 1e0 170 Ise 260 210 220 230 200 250 (29) There were two high-pressure cylinders placed outside the I frames and driving on a trailing wheel, and one low-pressure cylinder placed between the frames and driving on a wheel placed in front of the driving-wheel belonging to the high-pressure cylinders. The steam connexions were such that the' two high-pressure cylinders were placed in parallel, both exhausting into the one low-pressure cylinder. The first engines of this class were provided with high-pressure cylinders, 1r in. diameter and 24 in. stroke, a low-pressure cylinder 26 in. diameter, 24 in. stroke, and driving-wheels 6 ft. 6 in. diameter; but subsequently these dimensions were varied. There were no coupling rods. A complete See also:

• ACCOUNT
• ACCOUNT (through O. Fr. acont, Late Lat. comptum, cornputare, to calculate)

Worthington, Proc. Inst. C.E., 1889, vol. xcvi. Locomotives have to start with the full load on the engine, consequently an outstanding feature of every compound locomotive is the apparatus or mechanism added to enable the engine to start readily. Generally steam from the boiler is admitted See also:

• DIRECT

Smith on the North-Eastern railway in 1898 have been built by the Midland railway. In these there are two low-pressure cylinders placed outside the frame, and one high-pressure cylinder placed between the frames. All cylinders drive on one crank-axle with three cranks at 120°. The driving-wheels are coupled to a pair of trailing wheels. A controlling valve enables the supply of steam to the low-pressure cylinders to be supplemented by boiler steam at a reduced pressure. For a description and illustrations of the details of the starting devices used in the Webb, Worsdell and Smith compounds, see an article, " The Development of the Compound Locomotive in England," by W. E. Dalby in the Engineering See also:

• MAGAZINE

In this arrangement the whole of the adhesive weight of the engine is used in the best possible manner, and the driving of the train is practically equally divided between two axles. The engine can be worked as a four-cylinder simple at the will of the driver. S. M. Vauclain introduced a Successful type of four-cylinder compound in America in 1889. A ' high- and low-pressure cylinder are See also:

• CAST (from the verb meaning " to throw "; the word is Scand. in origin, cf. Dan. kaste, and Swed. kasta; " cast " in Middle Eng. took the place of the A.S. weor pan, cf. Ger. werf en)

The component of a balance weight which is necessary to balance the reciprocating masses introduces a vertical unbalanced force which appears as a variation of pressure between the wheel and the rail, technically called the See also:

• HAMMER, FRIEDRICH JULIUS (1810-1862)

A convenient way of describing any type of engine is by means of numerals indicating the number of wheels (1) in the group of wheels supporting the leading or chimney end, (2) in the group of coupled wheels, and (3) in the group supporting the trailing end of the engine. In the case where either the leading or trailing group of small wheels is absent the See also:

• NUMERAL (from Lat. numerus, a number)

Used to some extent in France and Germany and considerably in England for passenger traffic of moderate weight. Engines of this class, with 78-inch driving wheels and the leading axle fitted with Webb's radial axle-box, gauges, for many years did excellent work on the London & North-Western railway. The famous engine " See also:

• CHARLES
• CHARLES (1270-1325)
• CHARLES (1421-1461)
• CHARLES (1525-1574)
• CHARLES (c. 1319-1364)
• CHARLES (Fr. Charles; Span. Carlos; Ital. Carlo; Ger. Karl; derived from O.H.G. Charal,latinized as Carolus, meaning originally " man ": cf. Mod.Ger., Kerl," fellow," A.S. ceorl, Mod. Eng. " churl ")
• CHARLES (KARL EITEL ZEPHYRIN LUDWIG; in Rum. CAROL)
• CHARLES [KARL ALEXANDER] (1712-1780)
• CHARLES, ELIZABETH (1828-1896)
• CHARLES, JACQUES ALEXANDRE CESAR (1746-1823)
• CHARLES, THOMAS (1755-1814)

In still rarer cases both a leading and a trailing bogie have been fitted. (6) Six-coupled " with bogie, or " Ten-wheel " type, 4-6-0. A powerful engine for heavy passenger and fast goods service. It is used to a limited extent both in Great Britain and on the continent of Europe, but is much more common in America. The design combines ample boiler capacity with large adhesive weight and moderate axle loads, but except on heavy gradients or for unusually large trains requiring engines of great adhesion, passenger traffic can be more efficiently and economically handled by four-coupled locomotives of the eight-wheel or Atlantic types. (7) " Six-coupled " total-adhesion type (all the weight carried on the drivers), 0 6 0. This is the standard goods engine of Great Britain and the continent of Europe. In America the type is used only for shunting. It is a simple design of moderate boiler power. (8) " Six-coupled " type, with a leading axle, 2-6ro. This is of American origin, and is there known as the " See also:

• MOGUL, MOCHAL, or MIGHAL

The type is, however, less in favour than either the ten-wheel or the eight-coupled " Consolidation " for freight traffic. (9) " Eight-coupled " total-adhesion type, o-8-0; now found on a good many English railways, and common on the continent of Europe for heavy slow goods traffic. In America it is comparatively infrequent, as total-adhesion types are not in favour. (in) " Eight-coupled " type, with a leading axle, 2-8-0. This originated in America, where it is termed the " Consolidation." In the United States it is the standard heavy slow-speed freight engine, and has been built of enormous size and weight. The type has been introduced in Europe, especially in Germany, where the advantages of a partial-adhesion type in increased stability and a larger boiler are becoming appreciated. Occasionally the American eight-coupled type has a bogie instead of a single leading axle (4-8-0), and is then termed a " Twelve-See also:

• WHEELER, JOSEPH (1836-1906)
• WHEELER, WILLIAM ALMON (1819-1887)

Current Developrnents.—The demand of the present day is for engines of larger power both for passenger and goods service, and the problem is to design such engines within the limitations fixed by the 4 ft. 84 in. gauge and the dimensions of the existing tunnels, See also:

• ARCHES, COURT OF