valve and piston
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Crankcase
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• provides mounting surface for
cylinders and external accessories• contains the engine’s internal parts• provides a tight enclosure forlubricating oil as well as means ofattachment to an airframe
Crankcase
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• most aircraft crankcases are made of castaluminum alloys.
• made by sand casting
Crankcase
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Opposed Engine
Radial Engine
Types
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• consists of two halves ofcast aluminum alloy
Opposed Engine Crankcase
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•
divided into distinct sections• can be as few as three or asmany as seven
• typically has four mainsections
Radial Engine Crankcase
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•
mounted at the front and bolteddirectly at the power section• supports the propeller sections• mounting points for magnetosand other engine accessories
ose !ection
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•
the reciprocating moton ofthe pistons is converted torotary motion of the crank"shaft
• supports crankshaft
bearings
#ower !ection
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•
houses the superchargerand its related components•
attachments of inductionpipes and manifoldpressure lines
!upercharger !ection
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•
mounting pads for fuelpump$ oil$ tachometergenerators etc
%ccessory !ection
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#iston
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• a cylindrical plunger thatmoves up and down$ backand forth within a cylinder
#iston
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•
draw fuel and air into a cylinder• compress the gases•
purge burned exhaust gases• transmit the force to thecrankshaft
#iston
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•
cast aluminum alloy• may exceed &''' (•
high as )'' psi or up
#iston
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the top surface directly exposed to the heat
of combustion
#iston *ead
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cut into a piston’s outsidesurface
holds a set of piston rings as many as six ring grooves
Ring +rooves
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portion between the ringgrooves
Ring ,and
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an enlarge area inside thepiston
provides additional bearingarea for a piston pin
#iston pin boss
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piston base is extended toform the piston skirt
helps align a piston n acylinder
#iston skirt
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the diameter of the pistonparallel to the piston boss isslightly less than thediameter perpendicular tothe piston.
Cam"+round #iston
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prevent leakage of gaspressure reduce oil seepage into the
combustion chamber transfer heat from the piston to
the cylinder walls
#iston Rings
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prevent gas from escapingpast the piston
typically use two or threecompression rings
Compression Rings
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controls the amount of oil
Oil control ringsOil scraper rings
Oil Rings
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#i #i
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#iston #in
! i
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held tightly in place by asetscrew that preventsmovement.
!tationary
! i" ti
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allows little movement
!emi"-oating
( ll" ti g
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free to rotate in both theconnecting rod and thepiston
(ull"-oating
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alves
alves
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regulates the -ow of gases intoand out of the cylinder each cylinder has at least one
intake valve and one exhaust valve intake valves operate at lower
temperatures
alves
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alves
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metallic sodium melts andtransfer heat to the valve
stem where the heat isconducted away by thecylinder head
alves
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alve (ace
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creates a seal at the intakeand exhaust ports
provides a uniform sealingsurface
alve (ace
alve !eat
alve +uide
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provides support to thevalve stem
holds the valve face /rmlyagints the valve seat
alve +uide
alve !prings
alve !pring Retainer
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holds the valve springs inplace
alve !pring Retainer
alve Operating 0echanism
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alve Operating 0echanism
Camshaft
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transform the circular motionof the crankshaft to the linearmotion needed to actuate a
valve driven at one"half the
crankshaft’s rotational speed
Camshaft
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alve lifter or tappet
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transmit the force of thecam to the push rod
transmit the motion of thevalve lifter
pp
#ush Rod
Rocker %rm
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a pivoted arm mounted onthe bearing of the cylinderhead to open and close the
valves
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