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8/18/2019 Piston Design and analysis
1/22
Piston Design &
Analysis
2-Stroke ROTAX Aircraft Engines
ROTAX FLYING CLUB - 2001 ©
8/18/2019 Piston Design and analysis
2/22
Copyright ROTAX F 2
Piston Function
Transfer energy to the crankshaft
Control expansion under warm-up
8/18/2019 Piston Design and analysis
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Copyright ROTAX F 3
New pistons are
measured at
dimension “H”
Used pistons aremeasured at
widest point
Piston Measurements
8/18/2019 Piston Design and analysis
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Copyright ROTAX F 4
Compare piston to cylinder for clearance
and evaluation of suitability of cylinder
!ollow latest
specifications from
"ota# using only
genuine "$%A
Aircraft engine
parts
Piston Analysis
8/18/2019 Piston Design and analysis
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Copyright ROTAX F 5
Pistons are neit'er
cylindrical nor round
Pistons are made wit'special materials to control
e#pansion
Piston rings 'ave special
functions and design
Piston Design
8/18/2019 Piston Design and analysis
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Piston !ailureAnalysis
2-Stroke ROTAX Aircraft ngines
8/18/2019 Piston Design and analysis
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Copyright ROTAX F
Normal Pistons
Deposits vary fromoil ash, bron, tan,to black!bron"
#ight color $enoteshigher cylin$ertemperat%res"
#ight scoring is
normal, varnishfrom blo-by gasis normal
8/18/2019 Piston Design and analysis
8/22
Copyright ROTAX F !
Heat (ei)ure
E&cessive heat,over '2(()!*+(ET
#ean .etting ora$.%stments oncarb
/ncorrect loa$ing onpropeller alloinge&cessive R01
8/18/2019 Piston Design and analysis
9/22
Copyright ROTAX F "
Cold (ei)ure
Thermo-imbalance ofpiston an$ cylin$er
#ack of arm-%p
E&cessive temperat%re$ierence inlet too%tlet on engine"
8/18/2019 Piston Design and analysis
10/22
Copyright ROTAX F 10
*ac+ of *ubrication
E&cessive ateringestion ca%sing
loss of oil 3lm onintake"
#ack of intake air3lter service"
Res%lts in e&cessiveclearance
8/18/2019 Piston Design and analysis
11/22
Copyright ROTAX F 11
$il !ailure,$il !las'
4igh temp in enginefrom cooling system
fail%re, fan belt,coolant problems"
0oor 5%ality oils,a%to, gear,
%ns%itabletemperat%restability"
8/18/2019 Piston Design and analysis
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Copyright ROTAX F 12
#%brication on6ict
1i&ing of oils
Synthetic!1ineral
hemical reaction
8/18/2019 Piston Design and analysis
13/22
Copyright ROTAX F 13
1%lti fail%re
Overlappingsei7%res
)ail%re to repairOperator $enial
8/18/2019 Piston Design and analysis
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Copyright ROTAX F 14
Piston (cuffing
Sc%8ng one&ha%st si$e ith
no markscorrespon$ing onintake"
Thermal loa$ing
of oil 3lm $%e topoor 5%ality oil"
8/18/2019 Piston Design and analysis
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Copyright ROTAX F 15
Piston "ing,Cylinder (cuffing
Oil break$on $%eto9
/mproper break-in 0oor 5%ality oil
#ack of oil in mi&t%re
E&cessive loa$ing of
engine :propellerpitch;
8/18/2019 Piston Design and analysis
16/22
Copyright ROTAX F 1#
Piston Dome -rea+out
/gnition timingfail%re, erratic 3ring"
#ack of ignition$amper, pointsengines"
8/18/2019 Piston Design and analysis
17/22
Copyright ROTAX F 1
Piston Dome Detonation
0re-ignition,lea$ing into$etonation
A$vance$ ignitiontiming
Spark pl%g heat
range too high
#o octane f%el
8/18/2019 Piston Design and analysis
18/22
Copyright ROTAX F 1!
!oreign .aterial
1aterial $amage onpiston from $isplace$or intro$%ce$ ob.ect"
Disassembly re5%ire$of entire engine to3n$ any a$$itionalmaterial!$amage an$locate so%rce"
8/18/2019 Piston Design and analysis
19/22
Copyright ROTAX F 1"
Piston (coring,.aterial Damage
Ob.ects beteenpiston an$ all"
omplete
$isassemblyre5%ire$ to 3n$so%rce an$ allrelate$ material
8/18/2019 Piston Design and analysis
20/22
Copyright ROTAX F 20
Piston !ractureomplete$isassembly re5%ire$to remove all material
a%se from e&cessiveear, e&cessive R01ith no loa$,e&cessive clearance
3tting"
8/18/2019 Piston Design and analysis
21/22
Copyright ROTAX F 21
1%lti fail%re
arbon$epositsfo%n$ ithin
$amage$areas ofpiston, enginehas r%n aftera previo%sfail%re"
)ail%rethreshol$levels arere$%ce$
8/18/2019 Piston Design and analysis
22/22
Copyright ROTAX F 22
Sympathetic sei7%re
marks
0iston e&ha%st si$e 0iston intake si$e