Development of the Rolls-Royce Merlin from 1939 to 1945 A Lecture Delivered by Mr. A. C. Lovesey to the de Havilland Aircraft Company Technical Department in November, 1945 INCE the wat ended cumber of ris and /Arperizan Yeshnsians have visited Gecmany cays come tack with the same ory ‘the story of that ary. of German sclntits ‘who have been working with super exipment=— Supersonic wind-tantel, high alacude plans fog term planning of sos fantestle prjerts— fand one's most persuaded that ie must have een ft of amaters inthis country” ‘Butwen feat depondant east ms mind back oa aight spent ats certain seradrome watching the Mosauitesteke-of and spoed. on thar way te Beta with ther 4000 1b combs to return {ew fours ltr, bomb up again, fel. change ews a take-of! aga on he second mislon {none right, Ard som the end we won the nar. in spe af he Germans tesanes achievement Think azzin of ts Mosquito on is Nay {© ‘Retin-srely there must be some sory at the back oft The story. think, the work oF our technicians snd scents who proved to be move ‘hana match for ther German counterparts {er would say second to oe. Ts the Moceuto 8 gong camo ofthe part paved by Uevelopment in his county ‘New. anfortunateh, fom the. aucaft_ de- signees point of wew ‘he seroplane bie to have ome som of engine and I hoxs you wil ind some, interest ins brie outing of the development oF {his engine, ie. the Merin eis well Ksown that a Sompletely new design ‘of piston ensine takes nearly Hive yeas from the ie of ts nception une ean stert qanty peoation, and, Whi cow cess and projec, fst contioualy" go" on the develonen of ‘sting ype of Paremsunt importance during the war and i was largely de to such deselope ‘eat ha wo, were ble to ati sie ‘Nipetiority snd evenly numerical superonty over Garmany, Probably the statement numerical operon requires Ualifcation. One of he most elective methods of reducing production is {he Istredsction of raga) design changes, ut by properly coordinated development nessars dBsgn chagges can be land ahead an tered Sntothe nore! production fow. + +. 4 + Fin, 3tncrome in rate of elim of Spitive eg fom ets wage Sevcloprtont 218 fj Fig, 2—tncreate in speed. of esting from Merlin oogine ere mataly In the Roli-Royee Company the prcipe of developmacet is loses teated. te, production, Sted on uhat we may tm an “inition sian eure ete 1 trowel peferoance sod mechan flail fe puta nfo ‘redaction on Gamble landice so ha aher's pero of tine scone Hida new Mark ef enghe evolved witout lity rea In production The ergamnaion ofthe RoiieRoyeo Group bas boon panned 90 ths Fibelpe ste onal Dery pans mich was Fot ak out fr meas proctor ai sivest the Racin the 6 ith he ew inpenement and {ote eventual Btered gut iatd the man pro. Geng plant ate production aficulies hed Tink the Bee way to proceed wlth he tak isto ake you on a ice searsion through tho inst dan ‘of evelopment on ihe Men thsine an thon eplin te te main develay” inant protlers whl have bese techie “Tin developmen eavted 5 diferent Marks of engines ana you wise ate proces that ‘Sia ry csi design changes axe camied oat Sibu tn major aphetval io te prodeion ‘Geer this tume peried a tora of 150,600 Mextin cngines Were produced, including these mani —_ Fig: Atneronse fn speed of Mustang result trom Tatredicden of Marke tagae Courtesy of Harri Pihl | | | | Fig, L-Hncrease In brake horsepower of the - ‘Meclinengine fuctued in the USA. by the Packard Motor CCocapens, but his toi of 130,00 exalces those Ninn engine prosuced for United Sates Ale Tomes, Te raters prosioing thee engine: tere RolleRoyee Der, Crewe, Glisgow ad the Fore Moter Company and Packard. “rhe it series of Mntotions (numbers 1,2 43, 4and'5) shows bow the anima power fhe Merlin engine ined ring the war petod and th result of ths Upon sera performance, "Amore dele pete of the i given ia ioeretions numgers 7, 8'and 9 which show brow the rating of th Merlin engine was dele ‘ped to Koup pace mith the chaning phaser Of Sever “Coming now to specie developeen: items we con Tarsconvenenes, die thoy ito Ths fenecl chs {e) Inirevement of Use supercharse. (6) Improved fel (6) Delopment of mesheniat features to {ake cae ofthe ioprovements afd by Gand (b. Dealing wih Her (i can be stated chat he supercharger determinca the capacity, erm other ‘ores the ouiput ofthe engine, The peso Stil prevails thot the statis capacity known a3 ihe chops volume se the bass of comtbon the pole power output for diferent pes of ‘engin, but i ene the ease Becae the pt Stteecngine depends soley upon the mass ot IF ian be sao consume eet, and this sejeheseptare athe stint fois Tbs paasple apps Souaiy tan) en02° ‘urine engin hes be capable cea ith smb de which ean be “arried to Berl Aircraft Breinecringpene engine performance projctadand : ‘al i | ws } | i) - T_T = | | | the sreater mass flow: with respact 10 cooling, Freedews from detonation and cipal of with Standing high gas and inertia Loads (oe stra- tian 10) "At thi point [do not nish to make a ease for the liuid.eonkad engl, Davin the case 0 Fgter Grell Suen ae Moscuito, Spire ara Mustang ‘ere is ose thing Fcan say wth complete cor figcucs and thats that bad the Meri starved fs war aan af-ccoled engine, the performane> Increase whieh T have show you Would not have been rosie ‘Bufing the courte of research and develon= ment on superchargers (became eppesent (0 28 {hat any frie increase inthe ale pets TET ra noes ight shied by adoption a he ae aed aces ly 1946 weloprensmangine performar projets nce of (he Drevin engine necessitated the em- Dlosment of a two-singe sopercarger. Its am {aor ents 0 nace th eareson rato of supercharger, inher words the bocst pressure obtained at altitude, but naturally in Drier t get more horepowar out of tae engine tus has {0 be done etenty in order to avacd ‘ested pou in diving the Slower and exces temperifore of the charge for the comprssion Fatjo obtained. Trewould appear tht the wef limit of compzassion rt for the singe stage ‘supercharger |s about 4) and for compression Talos tad the i nec vo goa in0 stages. ‘This is show op clearly in Musration number Ie {should pint out tht before he dion ws made to adopr'a tnosiage mechanically deve blower, fll consideration was given fo the apple calla ‘of exaust turbos ard extensive analls ‘was made of this project Weal Hwa alleative In respect oF giving lower specie fuel consump. tons under cruising conditions it hed ery hie ‘Advantage in matimum power performance, Darueularly when ove consiars that with ¢ tobe ‘Stem we should lose precisely the whole of cue ector exhaust effect which we ko to be quite fficent at high spots, This, of coms, on? Iholds good when we use simple eestor exhaist smualolde The exhaust turbo eystem hag lot ot ddsedvantages in respect of toe arstllation sx figher alverat Like ihe ‘Spe, It came out Ieaver “than, the mechanically” driven super~ chiger and the drag eas evimgied (0 be Righee due fo various cooking ducts supplied for the {urbine, “Te system af control of the turbo blower was algo a cificult one, Te was quite evident that Seth Segard #9 the Spire, hich ‘yeh cfonlate onder constrain a fat tng the ob of smpeoving ie performance com tbe done inuch beter by means of @ wecharealy (diver twostape bioner The basic development for the twostege Fig. SMerlin devalopment to meet special Mighaltitude conditlont eer a = Plee S| . = i SN ari ¥ s+» raacte cence creprpn ratio and “iabacie etielency for shag rd =o ‘age Merlin superchargers ule we Full throttle power af Mero engines at fad i 29blower was WAR oul cout on the sapereherger rig arsommosate. Two. test, blowers Simultaneously, For the fist stage we used. a poled Vulture engine biower and. for the Second stage a Merlin 46 blower, On the super harger 7g the outlet from the Vulture blower ‘wes. coupled up to the inlet of the Merlin 45 Blower and tee rig could ooeraie the Blower at diferent speeds if necesary. The performance ‘charsterstes of eaon bloner were taken wea Funting fo combination aad fom these results all toe nosesary date was obtaired vath red {fo matching the io Sages so thatthe design of ‘the twovstage unt could be commenced, “The tmo-riage Clower vas constructed and was subjected fo development on the rig and when pplisd to the engine the results obtained Were p'shown in ilustration numbcr 12, The gain in engine poner at 30.0007. with the Twosstags Supercharger was. 300 hp. compared with the ‘Morin ao, or © ain, of teary 50 per ont of power. (Merlin 6, 1020 tip. at 30,000 ft Fig 12--Cut away ofewo: Speed, emostage suzer “agg Rargee (Coury Mite) ‘Metin 46, 220 hp, at 30,000 fe) ‘The result in tho around parformance of the Spltie was considerable, At 30,000 fe. the spood, ‘of the Spite 1X was 70 m,p.h. faster than the Spite V withthe Merlin 460 This may Ge some- ‘yh of an untlreomparson beeauze the Sptice ‘Vas nearing is ceiling at 30000 fe, but come pariag bot cseratt at. their rexpéctve. fall troll eights the Spite EX with the Metin 61 ‘war some 40 mph. faster than the Spire ¥. “The nest problem {0 tcekle was Tatersooing “The charge tecnperature nse relative tothe intake was 208 deg. G-st maximum fs. in the FS. gear dnd it was necessary to reduce the temperature in ‘der t get an inereesed densly of the charge and avoid detonation, Bothaircooled and laude ‘Cooled intercoolers were Investigsted and fight tested, but is bocame evident from te data abe ‘ined that the water cooled type nas most cuted fo our particular design of twontage super charger, [n'a singe seat tehter it was practically limpossibie to tse an siscooled inteeookt In Fig. M4—Secttonal drawing showing Rall Royce ‘erin twovtage sero engine 20 the space avilable, and the air ducting involved |nths form of intercooler Wasa serious litation tothe pilovs view. Having decided on a Ugulce cooled interosolcr 2 considerable amount of ‘etRenaine and rig work was carried outin order To arrive at the most suitable matrix to ave the ‘maximum heat isipaton without an undue ‘pressure Toss inthe duction system, Following be this lo af endorance texting une neces to prove cut the mechanical felblty of the ‘yet, Istrations 13 and 14 sow the arrange: ment of the intereooke system of the Mena chgine ‘In practice we fin that about 40 per cent inier- ecoling. gives about the best overall resus, Naturally, the more inteeooling we gst, or the lover the Charge tersperacur, the more poner tbe eine gives; but this hes to balanced up agaist {nore of” drag a6. the intercooler racater becomes larger. Generally itis found that there |S argpid gain in performance yp to about 38 pet ‘cnt inerenoling, but sfter tht the gan is ss ap. 1 should explain that for corventce we expres inercooling as percentage of the fen persiure rise akon Out by the intercooler. “The blower development 1 have, outlined brought us up to the time of the introduction of the Merlin G1 and. with rezard to aircraft per- formance, gave a very marked improvemsct Over the previous single sige engines. Musiation 18, shows the provement in performanes of & bomber azerat cue t0 the fing of two-stage cnginss, ‘We were now able 10 build up a lot of fake experience and we eould see that there mere gett Dosiblties of obtaining further mpproverenis ‘ih twosstage superchargers. One thing was very cvidentthat in order to obtain any appreciable Improvement in compression ratio we, should Krave to get Fd of te entry loses caused by the ‘crotetter, We had about reacted the limit of Grboreter’ Size consistent with saiifactny roetering and nere forced to look for ateratve ‘ethods of supelying fuel to the engine in the ‘correet proportions. gs real of our wud fair ang ie performance of 4 supersharged engine me ware Eble to derive the laws omvermg (ne rss fom of fir through the engine, it theelore. Seca Spparent that if we could contro the ful ow by these various factors to eve tbe nme relatonshi> \Weshould have an kde hel melering system Arrraft Engineeringi -rdex 5 bag a Figs 12—Allametal capsule contrt unit Now the pencil factors affting the charge fo he evne pm Door presurs, bockt temparature an exhaust back prowute and this am be expres Hythe formule i Won KN, "8 where Wa min and R= 422 for Metin Foch crn eae we nr wae riven af some rato ofthe engin peed in ‘hich tne stoke was proportion 0 ths boost Drsure minus ones of he exhanst Sock Bressre die bythe charge enpertute, ‘Avast stoke pump of outa te aeady ‘xine ina perpen. form produced bythe SUCudunster Company. 1 sew tensioad {6 velop the contol rochaaion fn wh the SHroks was conoid by boos res, atmo: ist buck pressure, Dat Wh open ‘hat pe a a ear aot aproaae foo, Mluzation the peneal arrange rment-of this parap ‘which belly consists of ie ‘hinges operated by a snasholit, the scoke OF can be varied by axial movement of an Inclined shft, This movement f produced by engine oll presse operating a servo piston and the ol pressure is regulated by «small spi valve. ‘Tais pit valve is fn turn controlled by 8 tack of capsules responding to changes of boost prestre, uly 1946 Fig. 6S. U. injection host temperature ond atmospheric pressure Aluscation 7), The corpiete metering pump has 4 isin petrol pump supplied for the purse ff charging the plunger poryp which does the ‘etering. The pamp can be driven ia any con venient Postion on the engine and the mvered fol canbe injected anywhere in the induction stem (Lustretion 18) Actually we selected te ‘ce of the supercharger asin this position ne Shines about 7 per sent improverven in com presion ratio of the Blower Gusto the tempera: {ure drop from fuel evaporation. Fig Diagram of RolleRoyce governor ‘antroled Injection pump’ eat) | D—Layout of §, Us Injection pump on ter Merlin engine sie vent Your pa sor war wad van ome Fig, 18-—Diagram ofinecton-pump system zaiTo accordance with our policy of faving en aterative insurance tem ve Geveloped Ia parallel a_centnifigel injection pump which {etuly does just the same job (llstrations 19 ‘and 20) fn this paryp we uses centrifagl Weis ‘opereting a poppet valve balanced. aginst. 2 apheagm. Tocease in speed tends to open the Doppst vale an allow the pressure to Dulld uP fee er ste of te ae Ts area ip frm reacts on the digphrogm with the result ‘hat the presure inthe chamber after the poppet salve nereas prosorticnaly to the square of the pani For'a given” postion of the. cio nitering needle andthe temperature metering oct, the Now through this onfice is prover tonal 9 the square root of the pressure: there: fore, we seta How from the outle: propsrtioal to speed. The Hack of eapsus aiaehed 10 the main meicting needle regulates the fuel ow in Correct prepardon to the boost pressure 2k Atmospherie pressure, wi te smal temperate fowgle cores the fw for charee tomparstare Utastration 1) ste [Returning now to superchargers; with ether of the naering pumps Thave cesrited we are at last abi to aimanate the rsaor source of pressure Inte ate inet and nko any cer change to the blower this eprosente maintaining the ‘Boost pressure for another 2.00 feet in altace (lsertion 21), We now eared outa nursber of shanges 10 the blower. Further improversents were made 10 the shape of the intake elbow, the ‘upertnrcr flor wee nreie I dame, Qsers were modibog, pressure foe between the fist ard Secon stages was considerably vedoced ‘wih tho resale that we ‘nore able 19 obeain s Compresion rao of 7-2 at 3000 vith an feral! eihaency cf 62 per cont which on the Devin feprents st 30,000 an erase in Inorsepaner of 400 hip. compared with our frst Seostage engine (llusutions 22 and 11). Sinee these cores were drawn furder improvements hhave been mada which Incense the etciney To GSpereentataCR-of 2, Improved Fuels “Ths development steps J have outlined looked she the performace st high siudes, but a he orscry stone cory Fig. Z1—increased performance of Merlin two-stage engine ome ime there was a gress demand for improved, performance at low slGiude, Now the chick Timiteion (apart ora schanieal ones) was detonation st high boast pressures. We ad pleaty Of boost presrure fo the’ Mein engine avelable Stow alétude ut with 100 octane ful we vere limited tox safe boost pressure of soout 20 1b, Jn, At this boost presure we could got aboat NRSD\np. Io the MLS. gear (stration 23) Fin, 22 (left), — Leese Gbadty “blower and ‘hreespaed gear Sharma oe Obviously ever fuels wore roqured. Ta order to Sioulete intcrest, Ne proceeded to carry. out ‘overload ests cn the Marin with Wes conan higher percontges of TEL. wich were mixes byourtives.Allthis was dane in order to demon= ‘rate both on th test bed ard in ight the Dpeovement ip performance which could Be b= {euned if we at bete Pal, cso that the engine ‘was capable of dealing with these higher ratines ‘Under comet coagitions. The fis ert ere run ‘sith 100 octane Tuck pls an adkliional 6 ce. ‘TEL gallon, bringing the (tal led eontent Up to iff cx, an with this we vere able to. exry 25 Ib. boedt wish a sale marsin fom detonation, “Ts increas “the vating of the engine UP 1S 20SD horsepower, which in tarn Inerased the perforce of the Spf at sea level by about B0 males hour and brought up the seed of the Mustang P'SIB to over 400 mllesfhour at Sea keel, Twas obvious that a fuel containing such a high percentage of TELL. would not be a pee. Til proposition or tevlee use doe 1 lead Touling dificultes eneounicred under ls? power rising conditions. Some single cylinder Work ‘was carried gut atthe RLALE, under Mr. Thomp- Yoo who bad found thai the addition of 25 per 2m move toni enn 0 sane fl Snereaed its knock rating coosideraby. Supy ‘of this fuel were made up for a fll seale ensine fest on the Merlin snd fain engine lest ests ‘more than coolirmed the LAE tests, At ths te there Was no production of this MEMLA. her ir this county or in Ameriea and, imme amass} “ne Atroraft EngineeringRees ed N\ Le WAT ok NTI if — eae BRAKE HORSE POWER ‘crgine development In 3 | lL Fig. 25--Spltfire performance projected and achieved by Merlin Mle 66 el) 7 wd : eo a i y | Greer t ui. — te ] ETT] tera 1997 1958 1999 1940 1941 194z 45 1944 1945 1946 * rae | BT F998 199) 140 AL aE AD HE TST 19 5 tr ae Fig. 24-Rolls Royce Mertin—progressive Improvement in power bi ccactataat 73 neal walgneypatnay rani wien sine, Fig. 27—Endurance at 3,000 or higher, Boost btely te value wos realized, stops were token {© predacesulcentsupees ints country (0 {efor tha who fuel Consumation of Fighter ‘Command. By the ine of he introdveion of ts {uel into the RAL. the whole range of Merlin ‘ies We apron oprah! Gost “The is operon ue of thi el was aginet the fying bombs ts the middle of 1948 Subsee gqeniy the whole of A.D. was put onto hs fet Tater it vas used by the Seeond Teele ‘Air Fores daring and aftr th evasion of the Goatinent. ‘The Ame:kens prompiy eowed sult end sed this Briss produced fel in theit ‘cor akters of al kinds, ‘Tae top curve of station 24 shows te ro resne tmprovencrts in poner of the Mein Enaice over the years of var. Tho citer show {he date on wich he type test proved he various ‘ings, You wl soe we have daw ai et ‘P800'hp which represents 8 racial makina ows fs rom dtnaton ot he Mein ent Borie octane Sine 0 2050 fp. epree feats cbout the bet which san be dane nit 400 octane fin plas water snetion The oe #¢ 240 ho. eeotesets the Km on 130 ease ‘Short endurence tests were carried out neatly a year ago using 130 grade fuel plus water In- tion and « pover of 640 bsp, vas obtained rom the Merlin egice at 361b, boost (BALE, ADA .g te, LNLESP. 895 Ib/30. 18) {eis only reasonable to expect the! appreciable mechanical changes had to be made to tre Merlin ‘engine {fos time to ime t take care ofthis poner Increase, Pracikally the whole ofthe engine ft ‘changed over this period, including the strengthe ening. up of the crankease, pistons, connecting | Tous, lingers, ete, but it interesting to reer uly 1546 Evmulative Sot tor ail fo the curves shown in the bottom eure of Hgtraion 24, Here we scevthat in spite of the sgooera strngiherine up of ths engine, which, of ‘our, involves the sition of weght the cue Shows’ steady dmprovement in’ the specie veda ‘At the time ilstrations 26 and 26 were drawn sewer slo the tid cf-war and we could see the possibilty of sll Kesping ave and improving ‘opment Meri ezoo {hs pestoemance of the Mein engined ghtet para rei, Sine that time, howeer, the peture iN] das changed for two ressons—ihe advent of the | my |e tS 3. B00 & 3 2 t » qi yeas seas zp . = ese Es Ne — < 4 t soo | < 1 TI Te RATE OF CUM® L/MIN. MPH TASS: Fig 2h—tmproved pertormance of Mustang Il with Merlin RMI4S.M, (tk; 10) 23SSF SET BOTT ESOOETTT) fi, This ld to some tran gauge investigation TEUASLTY_WHTW CONTINUOUS OPERATING ON ff tha erankeace ou Tig and asa resut of the TR a Te en ep re) ieee! ‘aie seas mee eran where" In order not to hold up the work we continued. = | oat nme tees ht seat if See) cen eee ee ae a oe] Sau ats tos aa ee ae wee eer Ba ee ee asaate, Bese? | cTagsalne ep star weconmia al ae Sernan] ey Soe ces ect? ven | SCE $F acco | SE Tees sorte ig tie eh see |S) MPs |B sires eo tran cn see cea (SEE |e cee eee tes Tr Bras aes Ob as EA etek te ee a at srwosto srscnanono | fsicdaye tol ic engine rar bere) feel ares pO | Ee rs ae = : a eernes_| ul esa nc eh 2 genase 2 ens] ae a ae eae | ee ear ers ve Sao ay om pase nes om mee ie See feteaulstin ener Set cet awe cm csai| Sct i ot agen tis ee) Fes | ee ee ee sgn png ae (ores wore. ‘The illustrations 28, 29 and 30 show some of Seca | gia meeren ea met 27'S | amelonment, The second design change shown ‘the ist calls fora hitde explanation. The noe ‘mal system of ubrcaton ofthe becings covets 269 rap ano | Stadmitting of to each journal bearing and by BISTONS PISTONS, ‘oano of sutable rling cn growing the ol is Induoed into the joornal and fos under pressure Fig, 21—Development of R.M.14S.M. mechanical features fr improvedreliablltyandincreatedating the ig'eod bearing, sarsted by hecentatugal Force ofthe column of ol inthe crankshatt The Jet propcled Sghter and the ening of he war. ratings, Therefore basic overload text wax ‘BeTen dsadvantages of thi system ee hat a5 isteed of tying fo follow along this eure we sdopted, frst_wich the obiect of finding Ye Strom at sounmis vith ol a : have reluctantly called hak 9 power develop: techankel weaknesses of existing Marts of Seeds ‘As Sitio be Toes tert cram meat beyond what we have shown and the do- engines and soconaly with tne object of ariving GA “aeint Ge CoP pressure tives a reduction ‘velopment on the Merlin is taking the course of at & specification which would satisfactorily poss in jubrication to the big-onds with, increased Tongetrm relay under commercial operating this teat. The overload text wes to consist o¢ 100 1, Mbseslon tO ehe Uigends with, ‘reset conditions, hours ecduraace at 2000 rps. and 18 Ib, boost e‘should hes aa tocpeuce of ol how with iy. pressure odour objexx was to complete ths texte tnould Wks aa create Of 0 Poy Development of Mechanical Features to Take Care Without any adjustment or replacements. eee shade hema eras he of larored Power ‘We started this overload testing with a stand- creased to the extent thet the bigends ge ia. 1 was realized that the norms) servies type end production ‘Merin ¢6 but filed ‘due to sufficient ol, althouch the journal bearings can test, far fom being 2 good procf of therelabity Cracks in the crankcase ater 97 hours. Just to futon quite salsfoctorlly with the increased of the engine at it particular rating, as not make sure that this was rot a rozoe lelure we Clearance, ‘Sufldently ardoous to reveal quickly the meehe put another engioe up Tora similar tet but sgulo + Th order to overcome this defect we inrodvced anfeallimtations at the projected inereosed fled the crankcase after about the same running what ve ealed the end-to-end ol feed syetera ee [ceannca Cm MAIN BEARINGS FRONT, ou. ED FROM. Ree vawe ad Oi Fig. 2.—End-tovnd oll feed, Merlin crankshaft ms Aircraft Engineeringitlutrtion 2) i which we admit ot he eran: ‘Su at each end and sf our into ot our fal and based bearings by prewure and CF ore "This poseenes several audonal advan: {ges Ie makes posibe the core proportion. ng of ol tetweon the journal abd. besnd becrings hich cannot bs done ith the previous Systems Tt permits reduction in total oll Pow Became withthe ols system exces ol ras een { the journal bearings inorder to. provice tnough forthe bigend Searing egnes excelent enufsion and cleaning ofthe ol and penms Selon of grooves and hove ia the Journal earings therety very considerably inzeasing their lead carrying eapast ‘We fll into anasy trap th regard to redue ing the of ow an found hat sthough beating {obrietion wos eveellnt ne rn into touble with fon ring. uming Piston temperature measurements showed that a reduction i oll Bon appreciably raised. the Piston temperature which exolaned the Teton Forrng gurwning. We overcame this trouble by the simole device f puting some “ats on the hole dings of the journals and so permed fn rereased oll discharge, A mor loa Way of fooling afer the pston rings to nivale ot jets nda the pistons fe by a searate ellery [Bend soma he spot om he rings, This systems uncer tes and has proved sot effective, Bring 4 reduction In ston tem: perature of ar much 4 90 deg. "Another item which has piven rte to Jot of| {couble under cil operting conditions ithe burning of exhaust valves die to the high lead Content inthe fuel We have eaied outs Cone fiderabe amount of work on this problem, td tm plensed to say at afer 4 Toog struggle we appear to have arived at the anavee ‘lustration mariber 31 shows the new fxtures embod! i the Mein 100 engoe 'AS you all probably know, the present 100 ma Taniriows OF Sanna conPOVETTS oAnp. crib Eas UN Seas \ecobenow can \amucrow oar Biron actos (PavoN BEMES. bey AT Sor eh sinoaRO. \avrecen rranece| 56 LL SEARING Bic ave Fig 30—Develepment of LM, octane fuel contains $4 ces, of TEL; Pe gallon fogether with am amount of ethysene deo in {he form of an inhibitor, The objet of {Be i Ilbitor i 4 comer! the prodacis of combustion s,m. mechanical features for improved rallablityand increased rating of the TELL, from non-volatile lead oxides 10 Yolatie lead bromides which past out ith the ‘Shaws gases, ‘The difclty arises, however, under low tem- SSE oa aa A Tae ell. | [Eris eee | vane ste [ | aa} | | om Sena Hise) [ONT HEA a | ‘rte ore” | FEATURES NOT SPECIFIED TO BE AS THE —______, MERLIN 66 Fig. 31-Petocgs new features ofthe Meriln Mk; 100 engine 2Fig. 12—Progretsive increas - ‘osuling tn back of Predaniion perature conditions in the induction manifold fe to the boiling point of TELL. and ethylene fdbromide being widely dient "The boiling Point of te Tead being 200 deg C, and tat ofthe Gtaromide only 152 dag. C. Therefore, under cold tendons the inbibiter tends to part company ‘with the lead. Under adverse conditions we have found as mich as two to thee limes ae mh TEL. pe gallon prownt in certain cylinders wits practically no lead. dibromice to neutralize i {At28 deg. C. maximum TEL. # minimum TEL, $5 ce, averige TEL. $c) This of course, results in very rapid aitek ofthe exhaust valves. ‘On other cylinders which got an excess of exaylene. dibvomide apd. very lie Tad the txt insert erosion is very bad, resulting in apid loss of tappet clearance, Spark plugs are AMfeted ina slmfar way to the valves ‘Obviously the first approach to the problem is to get the lead dsttbuton right, We find on the Metin that this Tend. distribution is excellent down to about 30 deg. charge temperature a the Induction manifold but ater that it Bocomes yey erratic “A reat deal can be done with regard to the ful, The use of acetylenetetrabromie, whieh Fig. Early type Martin connecting-rod bole we has a boiling point sishty higher than the FEA, Greatly Sees i kping te fo con stitaark together under low femperature cond dione Test its onthe bench fave Deen very promising and fight tat are about o sommence Ffshertghe texts the rests are found tobe good it is posntle that suficicot quantits can be Proguted in this county. No Gout the Amer Eins mil follow suit he results are satisfoctory. ‘On the other and the Russians ‘wed eth bromide wid has boing point of 4 dg. nd alia her low frcsing feet, On one of 04 Heavy bornber raids our ara ha to refuel in Rta and the sparking plugs Were seal Soi Sith lead on their eturn fo England This problem of ad dstrsbation st low charge temperzturs is aso being eatered for on tater cooled engines by making the intercooler a heat changer. as vel as cooling the charge the figher temperature condiions fe automaealy covsled into the engine cooing sytem at low femperature and (prevents: the. change falling below 40 dep. C. On the non intereooled engines we are adding a small heat exchanger to do ths job, ‘A. moye fundamental sation, 9 thi prob lemis, ofcourse fuel ngection and ate present tmoment we have tho in the sourse of eeelon- "When the distribution is as good 28 we all get fuses ver long Tanning Sho sin eaeon forts found to Best valve seat wear and valve dstortion dae to Temperature pradents inthe cylinder head. The tinzortion has the efit of sight blow-by togsther vith local high stressing. and saising of the temperature of th fra tionote g a in the region of high sires concentration Carefl temperature chests mace of exhaust valves where distortion has been present have Thown aise in temperature of nearly 200 degC whee alight Blowcby has oxcurred. Tis problem is being tacked on the Merin ty a redesign of the end head which ensires more woifsm desnbation of water ound the ‘haunt valve seats. The result has been @ cot Sidarabie lowering of the average valve face temperature, and geting @ uniforms lemperature round the valve face, “The remaining stations show a few items of interest For example, priention, shown in Stustration 32, ‘63 you know the Marlin is ted with tame traps ‘with the object preventing the Keser daures of tlow-bask getting inte the industion Syke and so resulting In vstentbackies when ‘arming at high boost Tho lame taps ook ater {hese constons very stator atthe wl not eater for prevention. This picture shows at {he Sop’ a ormal iadieator diagram with a9 fegine running a¢ 3.000 rpm, and 18 1b, sn Soon The potot at which gnition cakes place marked and the diagram shows 2. smcoth ine {rouse in prescure ae the point of unin. The ‘Sd Ultram shone 3 Sung ‘pin rcs Before the spark occurs, which IP seualy the Polnt where the charges ed. Thinis also accom and fy a sbarp nse in pressure and 30u ‘Shscrve thatthe Peak pressures ae about wise © hgh oo vith & normal dagram. [ris ako ident hat there ts lange amount of negative ork ain doe fo compresing the Buming The third diagram shows stil arr increase in pressure a ignition occ fom the hot plug Fig, M—Photo-latic test of connecting-rod in fact it occurs very “The fourth diagram shows the point of fring to have taken olace before the init salve lone, Which immediately ignites the charge between the Fame trans and the eslinders TT requires only one or ti Sach cytes to heat the flame traps slfiiently for ignition to take blac ith main tank sige sng se to & com: isa lot to ask ofthe flame traps to eater for these conditions and the funcamental thing isto remove the source of the hot spot siving Tice to, eigniton. ‘The most prevalent sources Of Bouble are as follows: (1) Sourk plog invaciely tightened. (@) Internal gas leakage in the sparking plug betes the insulator and body of the pe, resulting n the plug rapidly heating up. @) Unsuitabie ype of plug Ive eosld provide fam: cater Yor these conditions ie would Ye an extremely dangerous move and would ultimataly recut in Some other fle such as pston Guraleg "Toe last ihustrations (oumsers 35, 34 and 28) show some fetures of the Connecting rod design, ‘The. frst picture shows the relatively. sharp thouldar lef between the tug for the connecting Fox bolt andthe connecting rod resulting in high fireee sonsectration and titimate ‘allure Unless purticoler care is given to the fisish and radius Between the hug end the rod. Tetensive photo east teste nere carried out and the next usta tion shows how tho sess concentration can be reduced by sultasle blending the bolt and rod ‘nih the lug. The next picture shows the result ‘Of this work in the form of a production cox: ecting Yad Tis think, concludes some ofthe high spots dn the development ofthe Merlin engine soon after the inlet valve PROFESSIONAL PUBLICATIONS ‘The Reyal Aeronautical Socety Sou Nar tot Vol. 30, No 4 adiceh faze Seine Oke wtb Wn Teed oa igi sd Pere tes 225 une, 1945 The Insta of Wading Pete oN pee ring Tete of Canada TH BRCINEERING TOURAL Monto) ‘The Inie ofthe arora Sconces TOURNAL Contd) uk MAE IE 0 bey ental eee shaken nis Samet Aioraft Engineering