Lesson 24 Safety and Performance Testers,There are many types of safety and performance testers for vehicle. The style and design depend on the test items, the vehicle style, the year of the tester, and the manufacturer. Diagnostic test lanes for passenger cars are described in this paper. It is integrated fully automatic testing lanes for passenger cars and light utility vehicles up to a GVW of 3500 kg. The test lane consists of an electronic console and three mechanical units which mounted in the floor, are: a side slip tester, a suspension tester and a roller brake tester.,The software, that controls the measurements, is designed for fully automatic testing. The operator can perform all tests one after the other without any need to interfere with the system. All the operator has to do is to drive the car and to watch the results on the screen. After each test, the measuring result of the particular test is shown. After completion of all tests, a summary report is shown on the screen.,1. The Side Slip Tester The side slip tester is a steel plate that can roll sideways on bearings. When the operator drives a wheel of a car over the plate, the tire may move the plate sideways. These forces arise among others, when the toe setting of an axle is out of specification. The side slip tester measures the distance in meters over which a wheel of an axle is dragged sideways, when the other wheel of that axle runs straight for one kilometer.,The main influencing factor of the measurement is the total toe adjustment of the axle. The alignment is set to have all wheels run straight forward at cruising speed. The wheels should also run parallel to the car centre line. The side slip reading will correspond to a toe adjustment between the dynamic toe value and the static toe value. The operator must always drive over the side slip tester at walking speed.,He should avoid that the car body moves up and down, as this causes bump steer. When the side slip tester measures more than 7 m/km effective toe-in or toe-out, the operator must cheek the wheel alignment. When the measurement is between 4 and 7 m/km effective toe-in or toe-out, the operator is advised to check the wheel alignment.,2. The Suspension Tester The suspension tester measures the spring system of a vehicle. The quantities, related to vehicle parts, that influence the measurement, are from top to bottom: body mass, body spring, shock absorber, wheel mass and tire stiffness.,Also the stabilizer bar can influence the measurement. Each wheel is sequentially brought into vibration with a fixed amplitude and with frequencies from 0 to 25 Hertz. During this vibration the variation of the vertical wheel load are measured. After the measurement the measured data is analyzed according to different methods.,The suspension tester consists of two measuring plates that sequentially vibrate sinusoidally with a variable frequency and a constant amplitude. The tester measures the dynamic vertical force that the wheel exerts on the measuring plate. After the measurement of the two wheels of an axle, the measured data are processed and the results are presented on the screen.,The available measurement method is Eusama which has the Damping method and the Altus Speed method. 1) Emama The Eusama value is an internationally recognized measure for the road holding safety of a vehicle. It shows how well the suspension parts can keep the tire in contact with the road under worst case conditions.,It is a measure for how well the suspension can transmit the braking forces during an emergency stop. The computer compares the measured adhesion value with rejection limits that are stored in memory: 0 to 20% Dangerous, 21 to40% Fair, 41 to 60% Good, more than 61% Excellent. A difference Left/Right that exceeds 20% should be investigated.,The Eusama value is sensitive to the tire stiffness and to the weight of the vehicle. Please note that the Eusama value is measured at the relatively high frequencies between 12 and 24 Hertz and so the Ensama value does not necessarily correlate with what the drivers feels when he enters a corner with the vehicle.,2) Damping The Eusama value is sensitive to the tire stiffness and to the weight of the vehicle. Please note that the Eusama value is measured at the relatively high frequencies between 12 and 24 Hertz and so the Ensama value does not necessarily correlate with what the drivers feels when he enters a corner with the vehicle.,With this method the Wheel Damping Factor of the suspension system is calculated. This value indicates how well the wheel bounce resonance is controlled by the shock absorber. For most cars the damping factor is between 0.2 and 0.4. A difference Left/Right which exceeds 0.05 should be investigated.,The damping factor is not dependent on the weight (and the load) of the vehicle, but depends on the ratio sprung to unsprung weight and the damping force of the shock absorber.,3) Altus Speed With this method, the speed is calculat