Packard V-1650 Merlin

{{short description|Piston aircraft engine}} {{Redirect|V-1650|the Packard-produced engine also named V-1650|Liberty L-12}} {{Use dmy dates|date=October 2019}} {{Use American English|date=April 2019}}  {{infobox aero engine |name= V-1650 Merlin |image= File:Packard Merlin V1650 7 2.jpg |caption= Packard V-1650-7 Merlin |engine_type= Liquid-cooled V12 piston engine |manufacturer= [[Packard]] |national_origin= United Kingdom/United States |first_run= August 1941 |major_applications= [[North American P-51 Mustang]] [[Supermarine Spitfire]] [[Avro Lancaster]] |number_built= 55,523 |developed_from= [[Rolls-Royce Merlin]] |developed_into= |variants_with_their_own_articles= }}

The '''Packard V-1650 Merlin''' is a version of the [[Rolls-Royce Merlin]] [[aircraft engine]], produced under [[Licensed production|license]] in the United States by the [[Packard|Packard Motor Car Company]].<ref name="Encyclopaedia of Aero Engines">Gunston 1995, p. 144.</ref> The engine was licensed to expand production of the Rolls-Royce Merlin for British use. The engine also filled a gap in the U.S. at a time when similarly powered American-made engines were not available.

The first V-1650s, with a one-stage [[supercharger]], equivalent to the Merlin XX, were used in the [[Curtiss P-40 Warhawk|P-40F Kittyhawk]] fighter and in [[Canadian Car and Foundry|Canadian-built]] [[Hawker Hurricane variants#Canadian production|Hawker Hurricanes]]. Later versions based on the Merlin 60 series included a more advanced two-stage supercharger for improved performance at high altitudes. It found its most notable application in the [[North American P-51 Mustang]] fighter, improving the aircraft's performance making them capable of escorting Allied heavy bombers to Germany or Japan and back.

==Design and development== [[File:Packard V1650.jpg|thumb|right|Packard V-1650 in [[Deutsches Museum]] München]]

At the outbreak of World War Two, the British aviation industry expanded greatly. There was great need for the [[Rolls-Royce Merlin]] engine with shadow factories being established in Crewe, Manchester, and Glasgow. This was not enough to meet increasing demand with the British government looking to expand production using U.S. manufacturers. An agreement was reached between Rolls-Royce and the [[Packard Motor Car Company]] in September 1940 to manufacture the Merlin under license, with a $130,000,000 order being placed. The first Packard-built engine, designated '''V-1650-1''', ran in August 1941.<ref>Lumsden 2003, pp. 215–216.</ref><ref name=Time>[https://web.archive.org/web/20101014075256/http://www.time.com/time/magazine/article/0,9171,795076,00.html "Business: Ford's Rolls-Royces."] ''Time Magazine'', 8 July 1940. Retrieved: 26 August 2009.</ref>

The first American model was a version of the Mark XX, designated the V-1650-1 by the American military and the Packard Merlin 28 by the British. This engine used a single-stage, two-speed supercharger, the gear changing mechanism of which originally came from a French Farman patent license. The Merlin 28 was used for the [[Avro Lancaster]] bomber. The USAAF V-1650-1 version of this engine was used in the [[Curtiss P-40#Variants and development stages|Curtiss P-40F]]s. The initial Packard modifications to this engine changed the main [[crankshaft]] bearings from a copper-lead alloy to a silver-lead combination and featured [[indium]] plating. The bearing coating improved the break-in (running-in) and load-carrying abilities of the surface.{{Citation needed|date=August 2011}}

In answer to a request from the British [[Air Ministry]] for a high-altitude Merlin for the pressurised [[Vickers Wellington#Variants|Wellington VI]] high-altitude bomber, a Rolls-Royce team under the direction of [[Stanley Hooker]] developed a Merlin with two-stage supercharging, which became the Merlin 60-series. The first 60-series engine ran in March 1941, and was first flown in July the same year.<ref>[http://www.flightglobal.com/pdfarchive/view/1943/1943%20-%202161.html 1943 | 2161 | Flight Archive]</ref> When only 63 examples of the otherwise-cancelled Wellington VI were produced, these engines were instead introduced on the [[Supermarine Spitfire|Spitfire IX]] as the Merlin 61.

This model was later produced by Packard as the V-1650-3 and became known as the "high altitude" Merlin destined for the P-51, the first two-stage Merlin-Mustang conversion flying with a Merlin 65<ref>Harvey-Bailey and Piggott, 1993, p. 173</ref> as the [[Rolls-Royce Mustang Mk.X|Mustang X]] in October 1942, the production V-1650-3 engined P-51B (Mustang III) entering service in 1943. The two-speed, two-stage supercharger section of the two-stage Merlins and V-1650-3 featured two separate impellers on the same shaft that were normally driven through a gear train at a ratio of 6.391:1. A hydraulic gear change arrangement of oil-operated clutches could be engaged by an electric solenoid to increase this ratio to 8.095:1 in high speed blower position.<ref>Harvey-Bailey and Piggott, 1993, p. 178</ref>

The high speed gear ratio of the impellers was not as high as the ratio used in the [[Allison V-1710|Allison]], but impeller speed is not the only factor that determines engine performance, which is also a function of the size and pitch of the impeller blades. The gear-driven supercharger is a parasitic accessory; therefore, impeller gearing and blade profiles are carefully designed for maximum power at altitude without compromise of available power at the critical take off stage of flight. The double staging of the compressed fuel/air mixture provided the boost pressure through a diffuser to the intake manifolds that increased the [[critical altitude]] of the power plant.{{Citation needed|date=August 2011}}

The ability of the supercharger to maintain a sea level pressure in the induction system to the cylinders allowed the Packard Merlin to develop more than {{convert|1270|hp}} above {{convert|30000|ft|m}}.{{Citation needed|date=August 2011}} The two-stage impeller created extreme heating of the fuel/air mixture during the compression process, and, to prevent detonation of the compressed charge, it was necessary to cool the mixture prior to entry into the cylinders. The cooling was accomplished in an [[Intercooler#Air-to-liquid intercoolers|intercooler]] passage cast into the wheel case housing between the first and second-stage impellers <ref>Rubbra, 1990, p. 106</ref> and an additional cooling fin and tube core placed between the outlet of the blower and the induction manifold to the cylinders. [[Ethylene glycol]] coolant was circulated by a pump through these to carry off the excess heat generated by the impellers. Without the intercooler the temperature increase in the charge could be as high as 205 °C (401 °F).<ref>Lovesey, 1946, p. 220</ref> The glycol mixture used for cooling was independent of the main engine cooling system and used a centrifugal pump driven by the engine to circulate the coolant through an aircraft radiator system at a maximum rate of 36 U.S. gallons (136 litres, 30 Imperial gallons) per minute, depending on engine rpm.{{Citation needed|date=August 2011}} This combined system reduced the charge temperature to suitable levels.

Throttle valves in the updraft carburettor throat were controlled by an automatic boost control through the throttle linkage to maintain the selected manifold pressure with changes in altitude. The valves were only partially open during ground and low-level operation to prevent overboosting of the engine. As air density decreases with increased altitude, the throttle valves were progressively opened in response to the reducing atmospheric pressure. This system provided full power within engine boost limitations up to the critical altitude of {{convert|26000|ft|m}}.{{Citation needed|date=August 2011}}

===Measurement of boost pressure=== The British measured boost pressure as lbf/in2 (psi). The normal atmospheric pressure at sea level is 14.7 psi, so a reading of +6 means that the air/fuel mix is being compressed by a supercharger blower to 20.7 psi before entering the engine; +25 means that the air/fuel mix is now being compressed to 39.7 psi.

The Americans measured their boost ratings using [[inches of mercury]] (inHg). One pound-force per square inch equals {{convert|1|lbf/in2|inHg|3|disp=output only}} or {{convert|1|lbf/in2|kPa|3|disp=output only}}, and a standard atmosphere is 101.325 kPa =29.92 inHg =14.70 lbf/in2. In early Merlin engines the maximum manifold (boost) pressure was +12 on 100 octane fuel.<ref>Harvey-Bailey, 1983, p. 14</ref> This was increased in later models. {|class="wikitable" |- |Inches of mercury (inHg) [[absolute pressure]]|| Pounds per square inch of boost<ref>Gruenhagen 1980 p. 191.</ref> [[gauge pressure]] |- |81 inHg=||+25 lbf/in2 boost |- |66.5 inHg=||+18 lbf/in2 boost |- |60 inHg=||+15 lbf/in2 boost |- |46 inHg=||+8 lbf/in2 boost |- |42 inHg=||+6 lbf/in2 boost |}

===Postwar use=== In the United States many [[Military surplus|war surplus]] engines and airframes were sold relatively cheaply – two of the most popular items were [[North American P-51 Mustang]]s and Packard V-1650 Merlin engines, several of which were "souped up" and modified for air racing in the [[Bendix Trophy]], the Cleveland [[National Air Races|Air Races]],<ref>[http://www.airracinghistory.freeola.com/Cleveland%20Air%20Races.htm "Cleveland Air Races."] ''airracinghistory.freeola.com.'' Retrieved: 4 September 2009.</ref> and the [[Thompson Trophy]]. Many of these engines remain heavily used to this day in [[Drag Racing]], [[Hydroplane racing]], and [[Land Speed Racing]] at places like the [[Bonneville Salt Flats]]. The Mynarski Lancaster flown by the Canadian Warplane Heritage Museum in Hamilton, Ontario, Canada, one of only two Lancasters flying in the world, uses four Packard Merlin engines.<ref>[http://www.warplane.com/vintage-aircraft-collection/aircraft-history.aspx?aircraftId=4 Aircraft Details | Canadian Warplane Heritage Museum]</ref>

Work continues on increasing the power output of the Merlin for the Unlimited Class racers at the [[Reno Air Races]]. Innovations, such as the use of [[Allison V-1710]] connecting rods and the replacement of the intercooler with ADI (Anti-Detonation Injection) (50% Distilled Water and 50% [[Methanol]]), nearly identical in chemical composition to the Luftwaffe's wartime [[MW 50]] system, and similar to the [[water injection (engines)|water injection]] system used on Pratt & Whitney engines during World War II, have allowed great increases in power output.<ref>{{Cite web |url=http://www.enginehistory.org/Frank%20WalkerWeb1.pdf |title=Frank WalkerWeb1.pdf |access-date=7 January 2014 |archive-url=https://web.archive.org/web/20130202175128/http://www.enginehistory.org/Frank%20WalkerWeb1.pdf |archive-date=2 February 2013 |url-status=dead }}</ref><ref>{{Cite web |url=http://www.warbirdaeropress.com/articles/Modifications/Mods.htm |title=Going Fast – Modifications |access-date=28 January 2013 |archive-url=https://web.archive.org/web/20120402221528/http://warbirdaeropress.com/articles/Modifications/Mods.htm |archive-date=2 April 2012 |url-status=dead }}</ref> Many of the fastest Unlimited racers increase Merlin manifold pressures as high as 145 inHg (56.6 psi, 4.8 atm) to obtain up to 2,835 kW (3,800 horsepower), achieving Mustang speeds up to 490 mph.<ref>[http://warbirdaeropress.com/articles/Modifications/Mods.htm "Going Fast – Modifications."] {{Webarchive|url=https://web.archive.org/web/20110727084822/http://www.warbirdaeropress.com/articles/Modifications/Mods.htm |date=27 July 2011 }} ''warbirdaeropress.com.'' Retrieved: 24 September 2011.</ref><ref>[https://archive.today/20120717203412/http://www.airspacemag.com/how-things-work/cit-wilkinson.html "Masters of the V-12."] ''airspacemag.com.'' Retrieved: 25 September 2011.</ref>

==Variants== * '''V-1650-1''': {{convert|1390|hp|abbr=on}}; Based on Merlin 28, used in [[P-40 Kittyhawk]] and [[Curtiss P-60|Curtiss XP-60]] fighters * '''V-1650-3''': {{convert|1280|hp|abbr=on}}; Based on Merlin 63. * '''V-1650-5''': {{convert|1400|hp|abbr=on}}; Experimental. * '''V-1650-7''': {{convert|1315|hp|abbr=on}}; Similar to Merlin 66, primary powerplant of [[North American P-51 variants#P-51D and P-51K|the P-51D Mustang]]. * '''V-1650-9''': {{convert|1380|hp|abbr=on}}; Based on Merlin 100-series, 2,218 hp WEP with Water methanol injection. * '''V-1650-9A''': {{convert|1380|hp|abbr=on}}; as 9 with non-water injection for the P-51M * '''V-1650-11''': {{convert|1380|hp|abbr=on}}; Modified fuel system. * '''V-1650-21''': {{convert|1380|hp|abbr=on}}; Opposite rotation for [[P-82 Twin Mustang]] * '''V-1650-23''': * '''V-1650-25''':

==Applications== * [[Avro Lancaster]] B.III/B.X * [[Bell XP-63 Kingcobra]] * [[Curtiss P-40 Warhawk|Curtiss P-40F/L/Kittyhawk Mk.II]] * [[Curtiss P-60]] * [[de Havilland Mosquito]] B.VII/B.25 * [[Hawker Hurricane]] Mk.X, XI, XII * [[North American P-51 Mustang]] * [[North American F-82 Twin Mustang]] * [[Supermarine Spitfire]] Mk.XVI

==Specifications (V-1650)== {{pistonspecs |  |ref= |type=12-cylinder supercharged liquid-cooled 60° "Vee" piston aircraft engine |bore=5.4 in (137.16 mm) |stroke=6 in (152.4 mm) |displacement=1,649 in3 (27.04 L) |length=88.7 in (2,253 mm) |diameter= |width=30.8 in (781 mm) |height=40 in (1016 mm) |weight= 1,645 lb (746 kg)<ref name="Dry">No coolant or fuel.</ref> |valvetrain=[[SOHC]], two [[poppet valve|intake]] and two [[poppet valve|exhaust valve]]s per cylinder, [[sodium]]-cooled exhaust valve stems |supercharger=Two-speed two-stage, boost pressure automatically linked to the throttle, water-air aftercooler installed between the second stage and the engine. |turbocharger= |fuelsystem=Twin-choke updraft [[carburetor]] with automatic mixture control |fueltype= 100 [[Octane rating|Octane]], from mid 1944 100/150 Grade [[Aviation fuel]] |oilsystem=[[Dry sump]] with one pressure pump and two scavenge pumps. |coolingsystem=70% water and 30% [[ethylene glycol]] coolant mixture, pressurized. |power= Approx. 1380–1400 hp |compression=6:1 |fuelcon= |specfuelcon= |oilcon= |power/weight=0.80 hp/lb (1.73 kW/kg) take-off; 1.21 hp/lb (2.69 kW/kg) 100/150 grade fuel/MS gear. }}

==See also== {{Aircontent |related= * [[Rolls-Royce Merlin]] |similar engines= * [[Allison V-1710]] * [[Daimler-Benz DB 601]] * [[Junkers Jumo 213]] * [[Klimov VK-107]] * [[Mikulin AM-35]] |lists= * [[List of aircraft engines]] |see also= }}

==References== ===Notes=== {{reflist}}

===Bibliography=== {{refbegin}} * Bridgman, L. (ed.) ''Jane's fighting aircraft of World War II.'' London: Crescent, 1998. {{ISBN|0-517-67964-7}}. * Fozard, John W (editor).''Sydney Camm and the Hurricane: Perspectives on the Master Fighter Designer and his Finest Achievement''. Shrewsbury, Shropshire, UK: Airlife, 1991. {{ISBN|1-85310-270-9}}. * Gunston, Bill. ''World Encyclopaedia of Aero Engines (3rd edition)''. Sparkford, Somerset, UK: Patrick Stephens Limited, 1995. {{ISBN|1-85260-509-X}}. * Harvey-Bailey, Alec. ''The Merlin in Perspective: The Combat Years.'' Derby, England: Rolls-Royce Heritage Trust, 1983. {{ISBN|1-872922-06-6}}. * Harvey-Bailey, Alec and Piggott, Dave. ''The Merlin 100 Series - The Ultimate Military Development.'' Derby, England: Rolls-Royce Heritage Trust, 1993. {{ISBN|1-872922-04-X}}. * Hooker, Stanley ''Not Much of an Engineer.'' London: Airlife, 1984. {{ISBN|1-85310-285-7}} * Lovesey, AC ''Development of the Rolls-Royce Merlin from 1939 to 1945.'' Aircraft Engineering, July 1946, pp. 218–226. * Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. {{ISBN|1-85310-294-6}}. * Rubbra, AA. ''Rolls-Royce Piston Aero Engines: A Designer Remembers.'' Derby, England: Rolls-Royce Heritage Trust, 1990. {{ISBN|1-872922-00-7}}. {{refend}}

==External links== {{Commons category|Packard V-1650}} * [http://www.flightglobal.com/pdfarchive/view/1944/1944%20-%200591.html The Mustang – the longest-ranged single-engined fighter in the world] a 1944 ''Flight'' advertisement * [http://airandspace.si.edu/collections/artifact.cfm?object=siris_arc_362886 Packard V-1650 Merlin 12-Cylinder V Reports Collection 1941–1945 at the Smithsonian Air and Space Archives]

[[Category:1940s aircraft piston engines]] [[Category:Packard aircraft engines|V-1650]] [[Category:V12 aircraft engines]] [[Category:Liquid-cooled aircraft piston engines]]