piston design and analysis

8/18/2019 Piston Design and analysis

1/22

Piston Design &

Analysis

2-Stroke ROTAX Aircraft Engines

ROTAX FLYING CLUB - 2001 ©


2/22

Copyright ROTAX F 2

Piston Function

Transfer energy to the crankshaft

Control expansion under warm-up


3/22

Copyright ROTAX F 3

New pistons are

measured at

dimension “H”

Used pistons aremeasured at

widest point

Piston Measurements


4/22

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


5/22

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


6/22

Piston !ailureAnalysis

2-Stroke ROTAX Aircraft ngines


7/22

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


8/22

Copyright ROTAX F !

Heat (ei)ure

E&cessive heat,over '2(()!*+(ET

#ean .etting ora$.%stments oncarb

/ncorrect loa$ing onpropeller alloinge&cessive R01


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"


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


11/22


$il !ailure,$il !las'

4igh temp in enginefrom cooling system

fail%re, fan belt,coolant problems"

0oor 5%ality oils,a%to, gear,

%ns%itabletemperat%restability"


12/22


#%brication on6ict

1i&ing of oils

Synthetic!1ineral

hemical reaction


13/22


1%lti fail%re

Overlappingsei7%res

)ail%re to repairOperator $enial


14/22


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"


15/22


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;


16/22

Copyright ROTAX F 1#

Piston Dome -rea+out

/gnition timingfail%re, erratic 3ring"

#ack of ignition$amper, pointsengines"


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


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"


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


20/22


Piston !ractureomplete$isassembly re5%ire$to remove all material

a%se from e&cessiveear, e&cessive R01ith no loa$,e&cessive clearance

3tting"


21/22


1%lti fail%re

arbon$epositsfo%n$ ithin

$amage$areas ofpiston, enginehas r%n aftera previo%sfail%re"

)ail%rethreshol$levels arere$%ce$


22/22


Sympathetic sei7%re

marks

0iston e&ha%st si$e 0iston intake si$e

piston design and analysis

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