View source for Praga B2

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{|{{Infobox aircraft begin
 | name=B2
 | image=Jowett-Praga B.jpg
 | caption=Jowett-Praga B on display at the [[Shuttleworth Collection]]
}}{{Infobox Aircraft Engine
 |type=Air-cooled flat twin
 |manufacturer=Praga, Ceskomoravska-Kolben-Danek Co.
 |national origin=[[Czechoslovakia]]
 |first run=
 |major applications=
 |produced=
 |number built=135
 |program cost=
 |unit cost=
 |developed from=
 |variants with their own articles=
}}
|}

The '''Praga B2''' was a low powered [[Aircraft engine|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&nbsp;kW) aimed at lightweight aircraft.<ref name="JAWA38">{{Harvnb|Grey|1972|pages=32d}}</ref>  It was a higher [[Compression ratio|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&nbsp;hp (27&nbsp;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== -->
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==Applications (B & B2)==
*[[Alaparma A.M.10 Tucano]]
*[[AVEX Yakstas Racer]]
[[File:Yakstas LV-X095.jpg|thumb|Yakstas LV-X095 en EAA Gral. Rodriguez 2017]]
*[[de Schelde Scheldemeeuw]]
*[[de Schelde Scheldemusch]]
*[[Hillson Pennine]]
*[[Flying Flea|Mignet Flying Flea]]
*[[Praga E.114|Praga E.114/Hillson Praga]]

==Specifications (B2)==
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{{pistonspecs|
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|ref=Grey 1972 p.32d
|type=2-cylinder horizontally opposed
|bore=105&nbsp;mm (4.13 in)
|stroke=110&nbsp;mm (4.49 in)
|displacement=1.906 L (116 cu in )
|length=610&nbsp;mm (24.0 in)
|diameter=
|width=854&nbsp;mm (33.6 in)
|height=515&nbsp;mm (20.3 in)
|weight= 48&nbsp;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&nbsp;hp) at 2,440&nbsp;rpm
|specpower=16.3 kW/L (0.36&nbsp;hp/cu in)
|compression=6.7:1
|fuelcon=at 2,440&nbsp;rpm 9.38&nbsp;kg/h (20.68 1b/h)
|specfuelcon=0.225&nbsp;kg/hp/h (0.495 lb/hp/h)
|oilcon= 0.2-0.3&nbsp;kg/hp/h (0.44-0.66 lb/hp/h)
|power/weight=0.65 kW/kg (0.4&nbsp;hp/lb)

|designer=
|reduction_gear=Direct, right hand tractor.

|general_other=
|components_other=
|performance_other=
}}

==See also==
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|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]]