<!-- This article is a part of Wikipedia:WikiProject Aircraft. Please see Wikipedia:WikiProject Aircraft/page content for recommended layout. --> {{infobox aero engine | name=B2 | image=Jowett-Praga B.jpg | caption=Jowett-Praga B on display at the Shuttleworth Collection |engine_type=Air-cooled flat twin |manufacturer=Praga, Ceskomoravska-Kolben-Danek Co. |national_origin=Czechoslovakia |first_run= |major_applications= |produced= |number_built=135 |developed_from= |variants_with_their_own_articles= }}
The '''Praga B2''' was a low powered aero engine suitable for very light aircraft. It dates from the mid-1930s.
==Design== The Praga B2 was a dual ignition, air-cooled horizontal twin producing 40 horsepower (30 kW) aimed at lightweight aircraft.<ref name="JAWA38">{{Harvnb|Grey|1972|pages=32d}}</ref> It was a higher compression version (6.7:1 from the earlier 5.72:1) of the original and otherwise very similar '''Praga B''',<ref name="Praga"/> which provided 36 hp (27 kW). Its cylinders<ref name="JAWA38"/> were machined from alloy steel forgings and had aluminium alloy heads. The pistons were of aluminium alloy, with three compression rings and one scraper ring. The connecting rods were of nitrided steel, with divided big ends and bronze bushes at the little ends.<ref name="JAWA38"/> The one piece crankshaft was also formed from nitrided steel and had two main roller bearings and a single ball thrust bearing.<ref name="JAWA38"/> The single piece crankcase was cast from an aluminium alloy.<ref name="JAWA38"/>
135 units in all, including B and B2 variants were built.<ref name="Praga">[http://www.lompraha.cz/files/publikaceaj.pdf Praha history] {{webarchive|url=https://web.archive.org/web/20080913060147/http://www.lompraha.cz/files/publikaceaj.pdf |date=2008-09-13 }}</ref> Jowett Cars Ltd. of Idle, Bradford in the UK obtained a licence in 1936 to build the Praga B engine, for installation into the licence built Hillson Praga. Immediately after the end of World War II the Praga B2 was on display at the 1946 Paris Air Show.<ref>[http://www.flightglobal.com/pdfarchive/view/1946/1946%20-%202270%20-%200095.html Small engines at Paris Show ''Flight'' 21 November 1946]</ref> <!-- ==Operational history== --> <!-- ==Variants== -->
==Applications (B & B2)== *Alaparma A.M.10 Tucano *AVEX Yakstas Racer thumb|Yakstas LV-X095 en EAA Gral. Rodriguez 2017 *de Schelde Scheldemeeuw *de Schelde Scheldemusch *Hillson Pennine *Mignet Flying Flea *Praga E.114/Hillson Praga
==Specifications (B2)== <!-- choose one to copy here --> {{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=Grey 1972 p.32d |type=2-cylinder horizontally opposed |bore=105 mm (4.13 in) |stroke=110 mm (4.49 in) |displacement=1.906 L (116 cu in ) |length=610 mm (24.0 in) |diameter= |width=854 mm (33.6 in) |height=515 mm (20.3 in) |weight= 48 kg (106 lb) (with airscrew hub) |valvetrain=Two alloy steel valves per cylinder at 50°, aluminium-nickel-bronze valve seats. Two ball bearings to each rocker arm, grease gun lubricated in oil tight rocker-box. Push-rods and tappets in aluminium sleeves. |supercharger= |turbocharger= |fuelsystem=Zenith 42M, mixture passing through sump in pipe to avoid condensation. Two BTH magnetos supplying two plugs/cylinder. |fueltype= |oilsystem=Integral with 4.5 L (7.9 pt) sump. Pressure and scavenge pumps, filtered; pressure feed to big and little ends. |coolingsystem=Air-cooled, finned cylinders |power=31.1 kW (41.7 hp) at 2,440 rpm |specpower=16.3 kW/L (0.36 hp/cu in) |compression=6.7:1 |fuelcon=at 2,440 rpm 9.38 kg/h (20.68 1b/h) |specfuelcon=0.225 kg/hp/h (0.495 lb/hp/h) |oilcon= 0.2-0.3 kg/hp/h (0.44-0.66 lb/hp/h) |power/weight=0.65 kW/kg (0.4 hp/lb)
|designer= |reduction_gear=Direct, right hand tractor.
|general_other= |components_other= |performance_other= }}
==See also== {{aircontent <!-- include as many lines are appropriate. additional lines/entries with carriage return. --> |see also= |related=<!-- related developments --> |similar aircraft=<!-- similar or comparable aircraft --> |lists= *List of aircraft engines }}
==References== {{Reflist}} {{refbegin}} *{{cite book |title= Jane's All the World's Aircraft 1938|last= Grey |first= C.G. |year=1972|publisher= David & Charles|location= London|isbn=0-7153-5734-4 }} {{refend}}
==Further reading== {{Commons category|Praga B}} *{{cite book |title=Jane's all the World's Aircraft 1947 |editor1-last=Bridgman |editor1-first=Leonard |year=1947 |publisher=Sampson Low, Marston & Co |location=London |page=37d}}
Category:Boxer engines Category:1930s aircraft piston engines