Figure 20 – uploaded by Charles McCartan

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Fig.20 4stHEAD model of MM spring at 16 mm deflection — Figure 20 4stHEAD model of MM spring at 16 mm deflection

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We have added three further papers below [10-12] at the end of the Reference section, as interesting background reading. While these authors claim to model valve springs, even progressive wound valve springs, none of these papers presents any experimental evidence of

Fig.3 Basic valve spring geometry for the five test springs

Fig.5 Valve spring coil spacing for the five test springs Fig.4 Information on valve spring coil spacing THE VALVE SPRINGS (PART 1)

Fig.6 Three separate load measurements for a valve spring

Fig.7 Three separate stiffness measurements for a valve spring

Fig.8 ANSYS FEA mesh model of the ‘KW inner’ spring springs in the ANSYS [1] FEA software, including the ‘KW inner’ spring. The model was set up using the data from Figs.3 and 5. The computational mesh for it is shown in Fig.8. Depending upon the number of elements involved, in this case with some 4150 elements for the entire spring, the computation moves in about 0.1 mm deflection steps from free height to near coil bind. For the ‘KW inner’ spring this takes some 1.86 hours on a 3.0 GHz single processor running Ansys Workbench v11.0 on a Windows XP 64 bit system.

Fig.10 Model of spring deflection used in 4stHEAD Fig.9 Measured and FEA computed stiffness of ‘KW inner’ A MATHEMATICAL MODEL FOR SPRING DEFLECTION UNDER LOAD

Fig.11 Screen snapshot of both 4stHEAD computation models risen incrementally but the deflection has not.

Fig.12 Measured and computed stiffness by FEA and 4stHEAD

Fig.13 Stiffness modelling by FEA and both 4stHEAD models

Fig.14 Measured and 4stHEAD computed stiffness of ‘KW outer’

Fig.15 Static and dynamic modelling by 4stHEAD of ‘KW inner’ unchanged, the ensuing spring mass and stiffness are also virtually unchanged (35 N/mm and 54.8 g) but the deflection of the spring from its free height to coil bind is reduced from 32.73 mm to 30.08 mm. The use of ovate wire for the (normally less stiff) inner spring gives greater design flexibility without sacrifice of spring deflection before coil binding; this is often a real valve spring design issue for those engines with high valve lift characteristics.

Fig.16 Measured and 4stHEAD computed loads of HM springs

Fig.17 Measured and computed stiffness of ‘HM outer’ spring

Fig.18 Measured and computed stiffness of ‘HM inner’ spring

Fig.21 Measured and computed basic data for the five test springs

Fig.22 Natural frequencies of the five test springs REFERENCES deflection nears coil bind reflect the declining values for the mass of the active coil elements. Consequently, one can logically neglect from technical consideration any natural frequency values in the last millimetre (or so) of spring deflection. The two HM springs have very similar natural frequency levels for most of the valve lift in the range of 440 to 460 Hz. The important design issue here is that one should arrange for the valve lift profile for the HM engine to have low excitation acceleration harmonics in this frequency range. A similar logic applies to the KW springs, and to a lesser extent the MM spring, but with progression these springs exhibit a much broader range of potential excitation frequencies.

Figure 20 – uploaded by Charles McCartan

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