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

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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]

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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]

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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]

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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]

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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

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THE DESIGN

Plummer block

Torque

transducer

Drive pulley

Test bed

• To be situated on trolley:

•Motor

•Clutch

•Oil pump

•Sump

•Heater

Camshaft

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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

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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