class class type cylinder steam locomotive designed mixed traffic duties initially later operated development basic principles established chief mechanical engineer previous class design prototype result modifications class construction locomotive operational parts locomotive classes prototype member class constructed grouping featured variant valve gear designed class set precedent subsequent cylinder designs compared favourably class type showed little improvement performance class built clear type smaller cylinders provided greater route availability total engines built class primarily eastern section network british railways gave valuable service withdrawn preserved background class mixed traffic prototype completed showed marked improvement performance predecessor designs tested freight local passenger trains success prototype encouraged management order batch government restrictions regulating locomotive production world war relaxed locomotive works committed undertaking deferred repair work temporarily slowed construction new locomotives resulted gradual completion class order works capacity permitted operational experience class prototype demonstrated capable peacetime passenger freight traffic mainline london anticipated increase traffic require powerful locomotive capable hauling longer trains use larger engines prevented low permitted axle parts network caused economies track construction flint beach track ballast material failed hold track place strain support heavy locomotives meantime settled producing cylinder version class provided opportunity test variant valve gear developed assistant design construction detailed information valve gear numbering variations valve gear numbering completed plans new cylinder locomotive designated new design attempt increase operational flexibility power substantially increasing axle loading previous employment engineer involved class meant features class aid manufacture parts included use long travel free running speed right hand drive cab driving wheels retention wheel arrangement meant ample accommodation class tapered boiler class detail design left assistants brought functional influences design loading gauge friendly shape cab tender large diameter housed large valve anti vacuum retained valve gear outside cylinders main design differences class included cab exhaust arrangements addition extra inside cylinder frames drive centre driving axle revised layout cab spectacle plates small windows cab improve forward visibility incorporated large single glass boiler instead smaller windows class inside cylinder design valve gear consisted mechanical links fitted sets outside gear eliminating need separate set valve gear frames operate inside cylinder result reduction weight mechanical equipment located inaccessible locomotive valve gear design attempt address problems associated valve gear prone variations valve events caused heat expansion valve design utilised motion outside valve rods rods motion driving combination instead restricted space outside cylinders driving wheels impossible locate rocking arms controlling mechanism vicinity solution mechanism position pony truck ahead cylinders link outside valve rods extension accommodated strict loading gauge necessitated new design cylinder block outside steam set size cylinders reduced stroke diameter sides outside cylinders consequently sloped configuration similar cylinder locomotives providing ample space accommodate extension inside cylinder assembly set clear pony truck leaving space set independent valve gear frames mechanism prove unreliable service issue concerned strength locomotive frames cylinders taking inspiration cylinder locomotives designed suggested cylinders associated steam passages cast single block rectangular holes cut frames enable outside cylinders project established practice outside steam locomotives outside cylinders prevented design team resorted cutting gap frames accommodate outside cylinders secured place plate production limitations works prevented manufacture single casting incorporated cylinders meant cylinder split sections left inside cylinders forming single unit separate right hand cylinder casting new cylinder block design incorporated separate saddle casting configuration allowed cylinder patterns diameter creating standard component potential applications future locomotive designs prototype construction prototype railway works approved management commence works heavily engaged repair maintenance work caused government restrictions world war little spare capacity new construction projects particularly approval construction prototype coincided priority order cylinder class locomotives consequence works meant class locomotives completed june october seeing little sign increase production capacity decided construct prototype locomotive parts intended use class locomotive batch outside cylinders exchanged type railway works following casting construction class frames modified accept new design cylinder block produced robust chassis capable supporting sets valve gear provided gun points ease maintenance distinguishing feature locomotive high set class boiler pitched frames accommodate inside cylinder assembly potentially exposing mechanism elements prevent incorporated vertical metal cover beam protect inside cylinder valve gear assembly main visual difference class anticipated standard class chimney choke exhaust blast produced cylinders wider diameter cast locomotive new fabricated accommodate wide diameter cast chimney rest construction process followed specification final members order class locomotives built intended prototype completed december attached standard imperial flat sided class tender entered service march boiler pressure reduced psi psi fuel consumption compared cylinder class trials batch completion coincided absorption newly created grouping appointed new company embarked greatly expanded programme fleet replace inherited pre grouping designs participated series trials compare performance classes hauling freight trains loaded wagons despite achieving lowest coal consumption mile designs tested prototype cost maintain displayed poor steaming qualities affected trials remained sole ordered batch locomotives nos intention increase availability class complement newly introduced class passenger locomotives gauge restricted routes batch constructed works incorporated based operational experience given boilers set psi change valve gear difficulty experienced acquiring suitable spare parts prototype upgraded permanent way routes removing weight restrictions inspired use gear place free use separate sets valve gear driven centre driving wheels axle system easier maintain wide availability parts new locomotives completed march november noticeably different prototype mechanism outside cylinders omitted slab angled profile outside cylinders retained variations included set footsteps beneath beam class cast chimney design revised dome incorporated ease access routine maintenance complete nos attached flat sided imperial increase operational range longer eastern section routes locomotives ordered completion similar class capable undertaking broader range tasks intended intermediate passenger work driving wheels little disadvantage slower freight duties class construction history operational details class prototype initially based shed tests services eastern section familiar sight freight workings yard passenger trains increased train lengths duties designs allocation provided opportunity comparing performance cylinder class tests complete december moved shed passenger services allocated shed gauge restricted hastings line time proved ideal line allocated trials difficult route reading despite high maintenance costs steaming difficulties revealed freight trials prototype compared favourably class allowing management order final locomotives nos initially allocated central section shed regularly expresses brighton services hastings class moved shed operate hastings line whilst remained class allocated based central section haul trains london midland scottish railway class divided sheds preceding class capable hauling heavy loads moderate speeds useful attribute exploited second world war freight trains central eastern sections recorded hauling carriage troop special reading line april entire class operated hastings area build operation overlord targeted german fighter near undamaged entire class came british railways ownership performance class modifications development class class represented step forward british concept creating capable equally adept hauling passenger freight traffic prototype proved economical service percent coal class percent water design proved capable fast speeds reached mph trials run popular regular crews favoured way cylinders balanced forces driving axle resulted improved riding characteristics low speeds whilst reducing mechanical wear effect track valve gear meant comparatively light locomotive weight restricted routes successful overcoming problems associated valve gear variant suffered poor maintenance regime caused difficulty expense producing non standard spare parts works main problems associated gear included inadequate moving parts connecting inside cylinder outside motion running high speeds caused uneven steam distribution cylinders respect prototype offered little advantage simpler cylinder locomotive rarely long distance runs western section modifications prototype boiler pressure increased psi operating pressure june introduction nos service allowed withdrawn rebuilding separate sets valve gear august modifications included moving valve new class type dome ease access routine maintenance addition despite opportunity upgrade imperial tender attached new class members retained smaller capacity imperial flat sided tender result modifications heavier locomotive benefited upgraded track eastern section interchange parts reduced time needed complete repairs rebuilt locomotive emerged works october displayed little overall improvement class proved ideal gauge restricted hastings route narrower profile allowed operate narrow bridges tunnels power enabled haul heavier trains predominant modification class undertaken gradual introduction small smoke plates fitted improve driver visibility result smoke experiments king arthur class retired replacement despite making modifications steam circuit classes saw reason drastic alterations class result final set modifications ownership second world war included removal mounted anti vacuum replacement wide diameter chimney type improve prototype standard class chimneys replaced class british railways central eastern sections justified fitting equipment alongside class withdrawal suitable work class began decline british railways ownership widening bridges tunnels hastings line enabled powerful class freight trains hastings following completion electrification class shed alongside members class haul local services central section reduction work brighton main line prevalence class precipitated shed london remaining work allocated class withdrawn service november numbering completed grouping initially ran dark grey white lettering numbering time boiler pressure june dark olive green green complemented plain white lining black borders yellow markings applied locomotives built second world war labour paint short supply class gradually matt black took place essential maintenance visits works included application sunshine yellow block lettering tender gradually replaced black prototype constructed batch class locomotives ordered series dark olive green prefix applied number denote locomotive allocated overhaul locomotives constructed march november numbered shortly prefix dropped added numbers general renumbering locomotive stock rebuilding prototype members class nos british railways class absorbed british railways like class counterparts given power classification british railways ownership class reclassified denoting brake power rating non vacuum goods trains locomotives retained locomotive emerge works british railways painted tender lettering class locomotives gradually british railways mixed traffic lined black red cream grey lining british railways crest tender numbering changed british railways standard numbering system prototype batch allocated series operational assessment capable class mixed traffic locomotive operate gauge restricted routes noted crews comfortable riding qualities class provided assistants precedent compact cylinder locomotive designs formed mechanical template class tank engine prototype offered little improvement performance class tested non restricted routes led initial reluctance management batch construction meant non standard valve gear proved expensive maintain consequent lack spare parts use separate sets valve gear batch eased maintenance improved parts prototype rebuilt specification batch creating robust capable good turn speed working heavy passenger freight trains revised valve gear layout subsequently applied cylinder class designs relatively early withdrawal pre dated era buying withdrawn locomotives scrap dealers british railways consequently examples class survived preservation
SECR N1 class