Jacobs R-755

{{short description|225 hp radial aircraft engine}}  {{infobox aero engine |name= R-755 / L-4 |image = File:Radial Engine EASM 4Feb2010 (14568077736) (cropped).jpg |caption = Jacobs R-755 on display at the [[Evergreen Aviation & Space Museum]] |engine_type= [[Radial engine]] |national_origin = |manufacturer= [[Jacobs Aircraft Engine Company]] |first_run=1933 |major_applications= |number_built = |developed_from = |developed_into = |variants_with_their_own_articles = }}

The '''Jacobs R-755''' (company designation '''L-4''') is a seven-cylinder, air-cooled, radial engine for aircraft manufactured in the United States by the [[Jacobs Aircraft Engine Company]].<ref name=Gunston>{{cite book|last1=Gunston|first1=Bill|title=World encyclopaedia of aero engines|date=1989|publisher=P. Stephens|location=Wellingborough|isbn=1-85260-163-9|page=85|edition= Fully rev. 2nd}}</ref>

==Design and development==

The R-755 was first run in 1933 and was still in production in the 1970s. With a [[Bore (engine)|bore]] and [[Stroke (engine)|stroke]] of 5.25 in × 5 in (133 mm × 127 mm) the [[Engine displacement|displacement]] was 757 cu in (12.4 L), power ranged from 200 hp to 350 hp (150 kW - 260 kW). The engine features steel [[Cylinder (engine)|cylinders]] with aluminum-alloy [[cylinder head]]s. An '''R-755E''' variant was developed for use in helicopters.

==Variants== ;R-755A1:The base-line direct drive production version.<ref name=JAWA5556>{{cite book| last= Bridgman| first= Leonard| title= Jane's all the World's Aircraft 1955-56| year= 1955| publisher= Jane's all the World's Aircraft Publishing Co. Ltd.| location= London|page=305}}</ref> ;R-755A2:300 hp variant. ;R-755A3:Similar to A1 but with Scintilla magnetoes. ;R-755B1:De-rated version of the R-755A to drive a fixed pitch airscrew.<ref name=JAWA5556/> ;R-755B2:De-rated version of the R-755A to drive a variable or controllable pitch airscrew.<ref name=JAWA5556/> ;R-755E:Up-rated engine with reduction gearing.<ref name=JAWA5556/> ;R-755EH:Developed to power the Jacobs Type 104 Gyrodyne.<ref name=JAWA5556/>

==Applications== [[File:Waco YQC-6 N15705 (6235199366).jpg|thumb|[[Waco Custom Cabin series|Waco YQC-6]]]] {{columns-list|colwidth=30em| * [[Anahuac Tauro]] * [[Beechcraft Model 17 Staggerwing]] (B17L, C17L, E17L) * [[Boeing-Stearman Model 75|Boeing-Stearman PT-18 Kaydet]] * [[Cessna AT-17 Bobcat]] * [[Cessna 195]] * [[Funk F-23]] * [[Grumman Ag Cat|Grumman G-164 Ag Cat]] * [[Kellett KD-1]] * [[Lascurain Aura]] * [[Morane-Saulnier MS.505 Criquet]] * [[Waco F series]] (YMF, YPF) * [[Waco Custom Cabin series]] (YOC, YQC) * [[Waco Standard Cabin series]] (YKC, YKC-S, YKS-6) * [[Waco CG-15|Waco PG-3]] (twin-engined powered version of Waco CG-15 glider, prototype only) }}

==Engines on display== * A preserved Jacobs R-755 is on display at the [[Arkansas Air Museum]].<ref>[http://www.arkairmuseum.org/engines/engine-jacobs755.php Arkansas Air Museum - Jacobs R-755] {{Webarchive|url=https://web.archive.org/web/20101203082656/http://www.arkairmuseum.org/engines/engine-jacobs755.php |date=2010-12-03 }} Retrieved: 31 January 2009</ref> * A Jacobs R-755 is on public display at the [[Aerospace Museum of California]] *A preserved Jacobs R-755 is on display at [https://www.supertaviation.ca Super T Aviation Academy] in Medicine Hat, Canada. * A restored Jacobs R-755A is on display at the [[House of Whitley]].

==Specifications (R-755-A1)== {{pistonspecs|   |ref=Jane's fighting aircraft of World War II,<ref name="BridgmanFAoWWII">{{cite book|editor-last1=Bridgman|editor-first1=Leonard|title=Jane's fighting aircraft of World War II|date=1989|publisher=Military Press|location=New York|isbn=0-517-67964-7|page=305|edition= 1995}}</ref> Jane's all the World's Aircraft 1938<ref name=JAWA1938>{{cite book |title=Jane's all the World's Aircraft 1938 |editor1-last=Grey |editor1-first=C.G. |year=1938 |publisher=Sampson Low, Marston & company, ltd |location=London |editor2-last=Bridgman|editor2-first=Leonard|pages=86d-87d}}</ref> |type=7-cylinder air-cooled radial piston engine |bore={{convert|5.25|in|abbr=on}} |stroke={{convert|5|in|abbr=on}} |displacement=757 cu in (12.4 L) |length={{convert|37|in|abbr=on}} overall |diameter={{convert|43.5|in|abbr=on}} |width= |height= |weight={{convert|505|lb|abbr=on}} |valvetrain=2 valves per cylinder, pushrod-actuated, sodium-cooled exhaust valves |supercharger= |turbocharger= |fuelsystem= Single Stromberg NA-R7A carburetor |fueltype=73 [[Octane rating|octane]] |oilsystem= One pressure pump, two scavenge pumps |coolingsystem=Air-cooled |power={{convert|225|hp|abbr=on}} at 2,000 rpm at sea level |specpower=0.32 hp/cu-in (14.8 kW/L) |compression= |fuelcon= |specfuelcon= |oilcon= |power/weight=0.48 hp/lb (0.8 kW/kg) |designer= |reduction_gear=Direct drive, right hand tractor |general_other= |components_other= |performance_other= }}

==See also== {{aircontent  |see also=

|related=

|similar engines= * [[Armstrong Siddeley Cheetah]] * [[Wright R-760]]

|lists= * [[List of aircraft engines]] }}

==References== {{reflist}}

==External links== {{commons category}} * [https://web.archive.org/web/20080609180228/http://www.lancastermuseum.ca/s,jacobsengine.html The Jacobs Engine - Nanton Lancaster Society] * [http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/8fe9769e3e0192fc8525670c006cc54c/$FILE/ATTH0K0R/TC121.pdf FAA Type Data Certificate Sheet - R-755] {{Webarchive|url=https://web.archive.org/web/20170901152345/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/8fe9769e3e0192fc8525670c006cc54c/$FILE/ATTH0K0R/TC121.pdf |date=2017-09-01 }} * [http://autoweek.com/article/classic-cars/jay-leno-welcomes-cessna-powered-plymouth-his-garage? Jacobs Engine Powered Plymouth Truck] {{Jacobs aeroengines}} {{US military piston aeroengines}}

[[Category:1930s aircraft piston engines]] [[Category:Aircraft air-cooled radial piston engines]] [[Category:Jacobs aircraft engines]] [[Category:Seven-cylinder engines]]