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Transcript of Rotax
Piston Design &Analysis
2-Stroke ROTAX Aircraft Engines
ROTAX FLYING CLUB - 2001 ©
Copyright ROTAX FLYING CLUB 2001 (C)
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Piston Function
Transfer energy to the crankshaft
Control expansion under warm-up
Copyright ROTAX FLYING CLUB 2001 (C)
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New pistons are measured at dimension “H”
Used pistons are measured at widest point
Piston Measurements
Copyright ROTAX FLYING CLUB 2001 (C)
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Compare piston to cylinder for clearance and evaluation of suitability of cylinder.
Follow latest specifications from Rotax using only genuine ROTAX Aircraft engine parts.
Piston Analysis
Copyright ROTAX FLYING CLUB 2001 (C)
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Pistons are neither cylindrical nor round.
Pistons are made with special materials to control expansion.
Piston rings have special functions and design.
Piston Design
Piston Failure Analysis
2-Stroke ROTAX Aircraft Engines
Copyright ROTAX FLYING CLUB 2001 (C)
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Normal Pistons
Deposits vary from oil ash, brown, tan, to black/brown. Light color denotes higher cylinder temperatures.Light scoring is normal, varnish from blow-by gas is normal
Copyright ROTAX FLYING CLUB 2001 (C)
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Heat Seizure
Excessive heat, over 1200F/650C EGTLean jetting or adjustments on carbIncorrect loading on propeller allowing excessive RPM
Copyright ROTAX FLYING CLUB 2001 (C)
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Cold Seizure
Thermo-imbalance of piston and cylinderLack of warm-upExcessive temperature difference inlet to outlet on engine.
Copyright ROTAX FLYING CLUB 2001 (C)
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Lack of Lubrication
Excessive water ingestion causing loss of oil film on intake.Lack of intake air filter service.Results in excessive clearance
Copyright ROTAX FLYING CLUB 2001 (C)
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Oil Failure/Oil Flash
High temp in engine from cooling system failure, fan belt, coolant problems.Poor quality oils, auto, gear, unsuitable temperature stability.
Copyright ROTAX FLYING CLUB 2001 (C)
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Piston Scuffing
Scuffing on exhaust side with no marks corresponding on intake.Thermal loading of oil film due to poor quality oil.
Copyright ROTAX FLYING CLUB 2001 (C)
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Piston Ring/Cylinder Scuffing
Oil breakdown due to: Improper break-in Poor quality oil Lack of oil in mixture Excessive loading of
engine (propeller pitch)
Copyright ROTAX FLYING CLUB 2001 (C)
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Piston Dome Breakout
Ignition timing failure, erratic firing.Lack of ignition damper, points engines.
Copyright ROTAX FLYING CLUB 2001 (C)
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Piston Dome Detonation
Pre-ignition, leading into detonationAdvanced ignition timingSpark plug heat range too highLow octane fuel
Copyright ROTAX FLYING CLUB 2001 (C)
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Foreign Material
Material damage on piston from displaced or introduced object.Disassembly required of entire engine to find any additional material/damage and locate source.
Copyright ROTAX FLYING CLUB 2001 (C)
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Piston Scoring/Material Damage
Objects between piston and wall.Complete disassembly required to find source and all related material
Copyright ROTAX FLYING CLUB 2001 (C)
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Piston FractureComplete disassembly required to remove all materialCause from excessive wear, excessive RPM with no load, excessive clearance fitting.