CEMB USA C73 (A) - Manual (Page 22)

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5.7 - Eccentricity measurement (optional) ►
The much enlarged fi gures show the outer tyre surface and axis of wheel rotation.
Fig. A - shows measurement of the total Peak-to-Peak eccentricity defi ned as maximum radial deviation of the tyre
surface.
Fig. B - shows measurement of the eccentricity of the 1st
harmonic, i.e. the eccentricity of that circle which “recopies”
the tyre shape, by averaging the local deviations of the tyre
from the round shape.
Obviously the P.P. measurement is normally greater than
that of the 1st harmonic. Tyre manufacturers normally supply
two different tolerances for the two eccentricities.
At the end of the balancing spin it is possible to automatically measure the eccentricity of the tyre through the SONAR
sensor installed on the guard. The sensor should be positioned by hand in front of the tyre tread.
GRAPH 1 : represents the actual Peak-to-Peak eccentricity.
GRAPH 2 : represents the eccentricity of the 1st harmonic. For a wheel in optimum conditions, such graph
should approach a straight line.
While rotating the wheel, the screen cursor indicates the current value, with the stage referred to the
eccentricity measurement sensor.
The following buttons are enabled:
: Start an eccentricity optimisation procedure (see
ECCENTRICITY OPTIMISATION ) .
: A box is displayed indicating the offset effect that that eccentricity of the fi rst harmonic measured
may have, at an average speed of 120 Km/h.
: Return to measurement screen.
GRAPH 1 - (yellow)
GRAPH 2 - (red)