<!-- This article is a part of Wikipedia:WikiProject Aircraft. Please see Wikipedia:WikiProject Aircraft/page content for recommended layout. --> {{infobox aero engine |name=Rapp 125/145 hp |image=File:Rapp-Motorenwerke,_Rapp_8-cyl_on_the_engine_test_bench.jpg |caption=The 125/145 hp Rapp Rp II eight-cylinder engine on the test bench at the Rapp Motorenwerke |engine_type=Inline piston engine |national_origin=Germany |manufacturer=Rapp Motorenwerke |first_run={{circa|1915}} |major_applications=Lohner B.V, Lohner B.VI |number_built= |developed_from=Rapp 100 hp |developed_into= |variants_with_their_own_articles= }}
The '''Rapp 125/145 hp''', also referred to as '''Rapp Rp II''',<ref name="Grosz2002-Rp">Grosz; Haddow; Schiemer. 2002. p. 477</ref><ref name="Gersdorff1981">von Gersdorff; Grasmann. 1981. p. 26</ref> was a water-cooled 90° V-8 aircraft engine built by Rapp Motorenwerke in 1915.
==Design and development==
The Rapp 125/145 hp V-8 engine design was derived from the earlier four-cylinder Rapp 100 hp design in 1915.<ref name="Keimel1981">Keimel. 1981. p. 461</ref> It had eight cylinders, arranged in two rows of four, with a reduced bore and stroke of {{cvt|115|x|140|mm|in|2}}.<ref name="Grosz2002-Rp"/><ref name="Eyb1918">Eyb. 1918. p. 125</ref>
An order of 40 engines of this type, destined for the Lohner B.V and B.VI training aircraft,<ref name="Grosz2002-Lo">Grosz; Haddow; Schiemer. 2002. pp. 13, 471</ref> was placed by the Austro-Hungarian Armed Forces around the turn of the year 1915/16.<ref name="Pierer2011">Pierer. 2011. pp. 14–16</ref> A few engines were also sold to the Bavarian Army, where they were installed on training aircraft, but were plagued with recurrent carburettor fires and soon removed from service.<ref name="Grosz2003">Grosz. 2003. p. 33</ref>
The design of the cylinders and the valvetrain reflected the design of the Rapp 100 hp four-cylinder.<ref name="BMW-Rapp125">cf. ''BMW Group Archives''. 125 PS Rappmotor (photo)</ref> The cylinders of each cylinder row were again arranged in pairs composed of two separate forged steel cylinder liners screwed into the pairwise cast cylinder heads.<ref name="Keimel1981"/> The cylinder heads had integral cooling jackets and were cast from steel in pairs and then machined.<ref name="Vogelsang1918">cf. Vogelsang. 1918. pp. 158–161</ref><ref name="Huth1914">cf. Huth. 1914, p. 180-183</ref> The valve seats, with the exhaust valve seats being water-cooled, were separately built parts which were screwed into the cylinder heads and could be easily removed for maintenance work.<ref name="BMW-Rapp125"/> Both inlet valves of the cylinder pair, and likewise so both exhaust valves on the other side, were pressed into their seat by a single pivoted leaf spring. The intake was oriented to inner side of the Vee and the exhaust was oriented to the outer side.
Each cylinder's exhaust and inlet valves were actuated successively from a single cam lobe on the overhead camshaft via roller tappets and rocker arms.<ref name="Huth1914"/><ref>cf. ''Der Motorwagen''. 20 January 1918. pp. 14-15</ref> The camshaft of each cylinder row was driven via a vertical timing shaft and bevel gears between the two cylinder pairs. Two magnetos were also driven from the vertical timing shaft and were located between the two cylinder rows.<ref name="BMW-Rapp125"/>
The crankcase was cast from aluminum<ref name="Keimel1981"/> in two pieces, parted at the center line in an upper and a lower part. The lower part had a different design compared to the previous Rapp engines. Instead of a relatively flat base it had a tapered design, with the oil pump installed on the lowest point.<ref name="BMW-Rapp125"/> The oil was routed via an external oil feeder line to the upper side of the crankcase and then distributed between the two cylinder rows to the main journals. In order to circulate the engine coolant separate geared water pumps were installed on the respective side of the crankcase for each cylinder row.<ref name="BMW-Rapp125"/>
The engine used two Zenith-type carburettors which were both located between the cylinder rows. Each carburettor fed one row of four cylinders.<ref name="BMW-Rapp125"/> Also preheated air could be provided to the carburettors via intake air pipes routed through the exhaust.<ref name="Grosz2003"/>
==Applications== *Lohner B.V<ref name="Grosz2002-Lo"/> *Lohner B.VI<ref name="Grosz2002-Lo"/> *LVG B.I (Ot) (training aircraft, built by Otto)<ref name="Grosz2003"/>
==Specifications== {{CSS image crop |Image = Rapp-Motorenwerke%2C_Österreichische_Marinesoldaten.jpg |bSize = 544 |cWidth = 352 |cHeight = 264 |oTop = 90 |oLeft = 0 |Description = Austrian marines at the Rapp-Motorenwerke, {{circa|1916}}. Rapp Rp II engines can be seen on the left. |Alt = Austrian marines at the Rapp-Motorenwerke, {{circa|1916}}. }} {{pistonspecs| <!-- If you do not understand how to use this template, please ask at Wikipedia talk:WikiProject Aircraft --> <!-- Please include units where appropriate (main comes first, alt in parentheses). If data are missing, leave the parameter blank (do not delete it). For additional lines, end your alt units with )</li> and start a new, fully formatted line with <li> --> |ref=''Eyb''<ref name="Eyb1918"/> |type=eight-cylinder, water-cooled V-8 piston engine |bore={{cvt|115|mm|in|2}} |stroke={{cvt|140|mm|in|2}} |displacement={{cvt|11.6|L|cuin|0}} |length= |diameter. |width= |height= |weight={{cvt|220|kg|0}} |valvetrain=two single overhead camshaft-actuated valves per cylinder |supercharger= |turbocharger= |fuelsystem= |fueltype= |oilsystem= |coolingsystem=Water-cooled |power={{cvt|130|hp|0}} at 1,400 rpm |specpower= |compression= |fuelcon= |specfuelcon= |oilcon= |power/weight= |designer=Karl Rapp |reduction_gear=Direct-drive |general_other= |components_other= |performance_other= }}
==See also== {{aircontent <!-- other related articles that have not already linked: --> |see also=
<!-- designs which were developed into or from this aircraft: --> |related= *Rapp 100 hp *Rapp 200 hp
<!-- aircraft that are of similar role, era, and capability this design: --> |similar aircraft=
<!-- relevant lists that this aircraft appears in: --> |lists= *List of aircraft engines <!-- For aircraft engine articles. Engines that are of similar to this design: --> |similar engines=
<!-- See WP:Air/PC for more explanation of these fields. --> }}
==References== {{reflist}}
===Bibliography===
*{{cite book |title=Austro-Hungarian Army Aircraft of World War One |last1=Grosz |first1=Peter M. |last2= Haddow |first2=George |last3=Schiemer |first3=Peter |year=2002 |publisher=Flying Machine Press |isbn=1-891268-05-8 }}
*{{cite book |last=Eyb |first=Robert |title=Fliegerhandbuch |publisher=R.C. Schmidt & Co. |location=Berlin |edition=3rd |year=1918 |language=de |url=https://catalog.hathitrust.org/Record/005346784 |oclc=9500053 }}
*{{cite book |title=Die Bayerischen Motoren Werke bis 1933: Eine Unternehmensgründung in Krieg, Inflation und Weltwirtschaftskrise |last=Pierer |first=Christian |year=2011 |publisher=Oldenbourg Verlag |language=de |isbn=9783486704440 |url=https://books.google.com/books?id=S1aliJMr9MAC }}
*{{cite book |title=Österreichs Luftfahrzeuge: Geschichte der Luftfahrt von den Anfängen bis Ende 1918 |last=Keimel |first=Reinhard |year=1981 |publisher=H. Weishaupt |language=de |isbn=9783900310035 |url=https://books.google.com/books?id=XIBGAAAAYAAJ }}
*{{cite book |last=Huth |first=Fritz |title=Motoren für Flugzeuge und Luftschiffe |publisher=R. C. Schmidt & co. |location=Berlin |year=1914 |language=de |url=https://catalog.hathitrust.org/Record/001646423 |oclc=11492610 }}
*{{cite book |last=Vogelsang |first=C. Walther |title=Der Flugmotor und seine Bestandteile |publisher=C. J. E. Volckmann Nachf. G.m.b.H. |location=Berlin-Charlottenburg |year=1918 |edition=3rd |language=de |url=https://catalog.hathitrust.org/Record/002101951 |oclc=62113315 }}
*{{cite journal |author=<!--Staff writer(s); no by-line.--> |title=Zur Konstruktion der Steuerung |journal=Der Motorwagen |date=20 January 1918 |volume=21 |issue=2 |pages=13–16 |publisher=Krayn |location=Berlin |language=de |url=https://catalog.hathitrust.org/Record/000638153 }}
*{{cite book | last=Grosz | first=P M | title=LVG B.I, Windsock Datafile No.98 | publisher=Albatros Productions | year=2003 | isbn=1-902207-53-X }}
*{{cite book | last1=von Gersdorff | first1=Kyrill | last2=Grasmann | first2=Kurt | title=Flugmotoren und Strahltriebwerke | publisher=Bernard & Graefe Verlag | location=München | year=1981 | language=German | isbn=3-7637-5272-2 }}
*{{cite web |url=https://www.bmw-grouparchives.com/research/detail/index.xhtml?id=1093133 |title=125 PS Rappmotor [...] Landheer |author=<!--Not stated--> |date= |website=BMW Group archives |publisher=BMW Group |access-date=25 December 2020 |quote= }}{{Dead link|date=August 2025 |bot=InternetArchiveBot |fix-attempted=yes }}
{{Rapp aeroengines}}
Category:1910s aircraft piston engines Category:Rapp aircraft engines Category:V8 engines Category:Liquid-cooled aircraft piston engines