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The newly developed optical measuring system allows adjustment of front and rear wheel angularities - toe, camber, caster - in assembly-line production. There is no need to align the car, since the measuring base for the angle alignment is formed by the car itself. Defined spring compression values and direct caster angle determination lead to higher accuracy. Adjustment is carried out directly on the assembly line. Measuring pits are not required. The working time for each car and the working area required, which are important cost factors, are markedly lower than with conventional instruments. The axle measuring system was developed for the VW Vanagon, but can also be used for passenger car chassis. This present paper describes the measuring principle, the optical and mechanical design of the device, and a statistical analysis of over 100 cars aligned by means of this system, in comparison with conventional measuring instruments.

The newly developed optical instrument for vibration analysis is based on the laser Doppler effect that can be used to measure the vibration velocity of object surface points. The new system “SOVAS” (Scanning Optical Vibration Analysis System) analyzes the vibration amplitude of whole surface areas by means of computer controlled laser scanning and fast Fourier transform of the velocity signals derived from Doppler frequency modulation. As results frequency spectra of single points as well as vibration patterns of up to seven simultaneously measured frequency ranges can be displayed. The presented paper gives a detailed description of “SOVAS” and some typical applications in vibration analysis of car body and engine parts.

Holographic analysis of vibrations on squealing drum brake systems is a useful method to localize vibration sources on drum brake components. The results described in this paper are obtained by combinations of holographic as well as classical vibration measurements. This report describes experiments and illustrates how results in preventing brake squeal can be obtained, and used as a logical basis for the efficiency of this method. As a consequence easier principles for suppression of brake noise can be developed. Experiments carried out on three different types of rear brake systems show, that the main part of noise (1 to 2 kHz) is transmitted by the backing plate. Improved constructions without any tendency to squeal are demonstrated. A main result of this new testing method is that the observations and experiments carried out are of a general nature and so they are easily transferable to other brake noise problems on drum brake systems.

Analyses of squealing disk brakes generally show main frequencies from 1 to 10 kHz. On a test stand holograms exposed by time average and double-pulse techniques are recorded from various types of disk brakes. Photographs of reconstructions from those holograms display a vibration pattern in a simple topographical map of fringes, which represents contours of equal vibration amplitudes on the brake components: That would be i.e. yoke-type or fist-type callipers, brake pads and brake disk. Holographic Vibration Analysis is a useful method for looking at these small vibration amplitudes to understand different mechanisms of coupling. Also it is possible to localize vibration sources in squealing disk brakes.

The use of a giant pulse laser with 30 ns double pulses makes it possible to holograph different phases of an object vibration within time intervalls from 100 μs to 1 ms onto the same plate. The vibration phases into which the first and second laser pulse are fired can be exactly preselected by means of an electronic trigger system. The simultaneous reconstruction of the holograms taken by the first and the second laser pulse generates on the object surface a system of interference fringes which are loci of equal displacement. Adjoining fringes correspond to displacement differences of half a wavelength of the laser's light. In this way, it is possible, for instance, to visualize the vibration pattern of car bodies and drive units excited by the running engine. The method of measurement and a hologram camera especially constructed for making double pulsed holograms of automobiles are described. Several examples of application are quoted in order to illustrate this technique.