Locomotive Data 9
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? m 1 u : / 7 LOCOMOTIVE D ATA LOCOMOTIVE T"PES The m o t iv e po wer requirements of railway s are r s e so varied , that eve y system mu t employ a numb r of diff erent types of locomotives with which t o is ss s r e handle its traffi c . It not po ible here to de c ib s all the types in common u e , but attention may be called to a few characteris tic features of locomotives designed for diff erent classes of service . Excluding such work as switching , logging and s r indu trial , the ma"o ity of locomotives are used in a s s ro d ervice , and thi may be divided into two gen ss s r . eral cla e , f eight and passenger In heavy freight work , a locomotive is required to exert a r r high t active fo ce at comparatively slow speed , s sse r r while in fa t pa nger wo k the t active force , is r when running , compa atively low , while the speed - is high . Horse power is measured by the product o r of tractive f ce and speed , hence it is frequently necessary for a passenger locomotive to develop as s - as r much hor e power a freight , even though the t ac tive forces exe rted by the two may be widely differ A s - ent . the boiler capaci t y limits the horse power , it follows that in proportion to the tractive force x ss e erted , a p a enger locomotive needs a larger boiler than one intende d for freight service . The r s equirement of fast freight and heavy , medium s s peed pa senger service are more nearly alike , and t he same type of locomotive can frequently be used for both these classes of work . 4 TH E BALDWIN Lo c o mo rxvs WORKS PASSENGER LOCOMOTIVES The fi rst req uirement of a fast passenger lo co m o is s ffi r tive u cient boile capacity . The principal featu res necessary to secure this are a large fi rebox r with ample grate a ea , a liberal amou nt of well disposed heating surface and proper provision for r u . r r s r ci c lation If la ge d iving wheel are requi ed , u s co a s and bit minou l is used a fuel , the fi rebox is su h r u ally plac ed back of t e d iving wheels , and the resulting overhang is carried on a pair of trailing wheels. This allows the necessary room for a wide and deep furnace . The fro nt end of the engine is r - p eferably carried on a four wheeled truck , and r s either two or three pai s of driving wheels are u ed . I n this way the Atlantic (4 -4 -2) and Pacifi c (4 - 6- 2 ) types have been developed . If the weigh t nec e s sary for adhesion can be carried on two pairs of s wheel , without overloading the rails , the Atlantic s s s type hou ld be u ed , a it is the simpler of the two . D r u ing recent years , however, the weights of pass enger trains have bee n increased to such an extent that it is frequently necessary to use the Pacific type . The various conditions u nder which the engine is to work must determine the preferable wheel arrangement . The American (4-4-0) and Ten-wheeled (4-6-0 ) types are used to a considerable extent in passen is ger service , but their capacity limited owing chiefly to the diffi culty of placing a wide and dee p fi - rebox above the driving wheels . The Ten wheeled r s w e type , however , with mode ate ized driving he ls , s is freq uently employed in heavy passenger, and fa t s s are freight service . The e wheel arrangement s s s s al o exten ively u ed abroad , where req u irement , s as . a a rule , are not se vere as in the United States The Ten-whee led type is espec ially s ui table f o r Lo c o mdrrvs D ATA 5 passenger service insouth America and Colonial b r cou ntries, and large num e s of these engines have been built by The Baldwin Locomotive Works for export . i When anthracite s u sed as fuel , a compara i l s f t ve y shallow fu rnace will u fi ce , and the grate can often be placed above the driving wheels. In this r s way t ailing wheels can ometimes be omitted where , s i s in a oft coal burning locomot ve of imilar capacity , they would be necessary on account of the boiler requirements . FREIGH T LOCOMOTIVES It is important in a freight locomotive for heavy se r e he vic , to have t maximum proportion of the total weight available for adhesion consistent with r . r r the conditions of se vice As a ule , the efore , ‘ r s se fo r s t uck wheel are u d only guiding purpose , and not because the design of the boiler requires s as is a r their in tallation , the c se with the t ailing s P fi wheel of Atlantic and aci c type locomotives . The great bulk of the freight traffi c in this country is handled by locomot ives having three or four pairs of coupled wheels , while in some cases fi v e pairs have been employed . If service conditions require the engine to run ‘ r s backwa d frequently, radial truck at each end of the locomotive are often use d . Such trucks aid r s in p eventing derailment , and reduce flange wear on the driving whee ls . They are also used at times t s s n in locomo ive de ig ed to bu rn low grade fuel , such as lignite , where an exceptionally deep furnace is r req uired , and the g ate cannot be placed above the driving- whee ls withou t raising the boiler to an execs 2 -6- sive height . I n this way the Prairie ( 2 ) and M 2 -8 -2 ikado ( ) type s have bee n develope d . The Prairie type has proved spe cially successful in fast s freight se rvice , while t he Mikado type is being u ed , Tan BALD WIN Lo co u o u va Wo nxs t o an c s t in eav s s s in rea ing exten , h y low peed ervice , because both wheel arrangem ents m ake possible t he u se o f a larger boiler t hanc o uld be provided in a similar locomotive with the same weight per driving a e but w r xl , ithout t ailing whee ls. ' ARTICULATED LOCOMOTIVES In cases where a locomotive of great tractive force is required , and the number of driving wheels neces sary is so great that it is not practicable to c ouple them all in one group , an articulated locomotive us s a s s may be ed . An engine of thi type h s two et of frames, which are connected by a hinge , or "oint . r s The d iving whee ls are divided into two group , and t he wheels of e ach group are rotated by a sepa f b r rate pair o cylinders . In this way a large num e of v s dri ing wheel can be used , and a correspondingly high tractive force developed while the rigid wheel base is that of one group of driving wheels only , and the engine can therefore traverse curves without f difi culty . The type of articulated locomotive most commonly i use d in America s known , from the name of its “ M " inventor, as the allet . This engine operates h s - ss on the compou nd principle , and a two high pre r s u e cylinders , which drive the rear group of wheel . - and two low pressure , which drive the forward group . The hinge pin connecting the front and r s is o n rear f ame placed the center. line of the engine - l between the high pressure. cylinders. The boi er h l s is e d in alinement wit h the rear frame , and is supported on the front frames by sliding bearings . When the engine enters a curve the front wheels h and frames act like a truck, and swing abou t t e as hinge pin a cen ter. A c ontrolling spring , mounted i t hro wn es on the front boiler bearing, s into compr s s ion , th u guiding the rear group of wheels into the LOCOMOTIVE DA TA r s e r c urve , and aiding in e toring the alinement aft the curv e has been passed . s s is e In a locomotive of thi type , team convey d from the throttle valve to the high -pressure c y lin ders through rigid pipes , which may be either inside or outside the boiler according to circumstances . The pipes leading from the high - pressure to the low t s pressure cylinders , and from the la ter to the moke r x . box , are necessa ily provided with fle ible "oints s s a r e s The e pipes carry team t mode at pre sures only , a fact which greatly lessens the diffi culty of keeping the "oints tight .