DYNAMIC MEASUREMENT OF THE FORCES IN THE FRICTION ...

For this reason it was necessary to develop a measurement method which enables recording
the movement of a brake pad during a braking. Finally a visual measurement method was
used with a resolution of 10.2 million pixel. With regard to the following photographs, a pixel
corresponds to 0.124 mm - this therefore also corresponds to the maximum precision of this
method. Fig. 19 shows exemplarily the movement of the finger-sided brake pad during a
braking with a braking pressure of 40 bar.
RESULTS
Fig. 19: Movement of a brake pad
during a braking with 40 bar
As expected, the brake pad is drawn in the direction of rotation. Furthermore, it easily
screws out intake-sided correspondingly to the acting forces. Therefore, the sensors move
outtake-sided insignificantly in the direction of the wheel's centre. For the determination of
the point of application of load, which is near the middle of the pad's back plate, it means in
this case a deviation of approx. 0.66 mm, which has to be added to the measured value. By
using other caliper types this value can turn out considerably greater, since frame brakes are
construction-relatedly considerably stiffer than e.g. simple finger brakes.
The indications of the positions of the sensors in the
brake pad for the following results correspond to
Fig. 20.
The course of the four sensors of the piston-sided
pad is exemplarily presented in Fig. 21 at a braking
pressure of 40 bar and a stationary brake disc. In
Fig. 22 is the course during a braking process with
an initial speed of 15 m/s (425 rpm).
- 9 -
1 2
3 4
Fig. 20: Indication of the sensors
in the brake pad