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AEROSPACE COATINGS LTD
CAMSHAFT AND TAPPET TEST RIG
PRESENTATION SUMMARY
Introduction Overview of the Camshaft and Tappet
system. Load conditions and environment Failure and wear The Rig Conclusions
AEROSPACE COATINGS LTDAEROSPACE COATINGS LTD
OVERHEAD CAMSHAFT WITH INVERTED BUCKET FOLLOWER
Overhead camshaft with inverted bucket follower is the configuration type selected for our Test Rig
Camshaft acts directly onto the tappet and directly actuates the valve
Stone, R, Introduction To Internal Combustion Engines [1]
AEROSPACE COATINGS LTDAEROSPACE COATINGS LTD
CAMSHAFT LOBE FEATURES
The Camshaft lobe has three main features
1) Ramp 2) Flank3) Nose
What are their characteristics?
AccelerationValve lift proportional to lobe radiusZero velocity at maximum lift (turning point)
Heisler, H, Advanced Engine Technology [2]
AEROSPACE COATINGS LTDAEROSPACE COATINGS LTD
LOAD CONDITIONS AND ENVIRONMENT
Diagram shows the force at the tappet with respect to camshaft angle The three curves
represent different engine speeds
Maximum force is not necessarily at maximum valve lift.
Inertial force overcomes spring force due to increased acceleration
Stone, R, Introduction To Internal Combustion Engines[1]
AEROSPACE COATINGS LTDAEROSPACE COATINGS LTD
FATIGUE FAILURE (PITTING)
Fatigue accounts for 90% of failure in metals
Biggest culprit of camshaft failure.
Cracks propagate under the surface due to shear stresses.
Correct materials selection and processes can prevent this.
Pitting and spalling on a cam lobe (above) and tappet (below)
www.tribology-abc.com [3]
AEROSPACE COATINGS LTDAEROSPACE COATINGS LTD
FAILURE ANALYSIS
Microscopy images Top image shows
formation of fatigue cracks and broken off material
Bottom image shows loss of material due to fatigue, combined with abrasive wear.
These images show camshaft surface fatigue and abrasive failure.
The cause of this is due to a build-up of Hertzian stresses under the surface.
X 50 Mag
X 50 Mag
AEROSPACE COATINGS LTDAEROSPACE COATINGS LTD
THE DESIGN
Plummer block
Torque
transducer
Drive pulley
Test bed
• To be situated on trolley:
•Motor
•Clutch
•Oil pump
•Sump
•Heater
Camshaft
AEROSPACE COATINGS LTDAEROSPACE COATINGS LTD
DESIGN FEATURES
Simulated valve mass.
Adjustment for valve spring compression.
Probe type displacement sensor attached to rod.
Section through tappet and housing
Shims to allow for larger or smaller springs
Dual spring retainers AEROSPACE COATINGS LTDAEROSPACE COATINGS LTD
DESIGN FEATURES
Oil grooves on tappetOil grooves on tappet
Shims allow for Shims allow for tappet rotationtappet rotation
Tappet configurationAEROSPACE COATINGS LTDAEROSPACE COATINGS LTD
CYLINDER HEAD TEST RIG
AEROSPACE COATINGS LTDAEROSPACE COATINGS LTD
Fiat 1.9 JTD engine in place on the cylinder head test rig.
CONCLUSIONS
The use of a Camshaft and Tappet test rig is highly beneficial Simulates dynamic environments
Results can be applied to all aspect of material testing. Excellent example of a harsh tribological environment
Fatigue testing Cost and time effective
Easy to analyse, prepare and set-up
AEROSPACE COATINGS LTDAEROSPACE COATINGS LTD
REFERENCES
[1] Stone, R – Introduction to Internal Combustion Engines, The Macmillan Press, 2nd Edition 1992, ISBN 0-333-55083-6
[2] Heisler, H - Advanced Engine Technology, Butterworth-Heinemann, 1st Edition 2002, ISBN 0-340-56822-4
[3] http://www.tribology-abc.com/poll/case03.htm-accessed 2/12/04 [4] http://www.hbm.com/products/ - accessed 1/04/05