"This SAE Recommended Practice provides procedures@ and information to conduct vibration (impact) tests on lighting devices and their components as well as other safety equipment used on vehicles. Rationale The SAE Heavy Duty Lighting Committee established the SAE Vibration Task Force to incorporate improvements in the SAE J577 Vibration Machine. The goal was to make the test results repeatable from machine to machine and lab to lab without changing the nature of the test. Members of the SAE Heavy Duty Lighting Committee and the SAE Lighting Committee were solicited for their input as to improvements made to their machines over time. The drawings referenced in this document represent improvements suggested by committee members as well as those developed through testing. 1. Cam followers were added to reduce friction and prevent wear. This should extend the interval between calibrations. 2. The 4 springs that produce the 290N ?? 20N force were replaced with a single compression spring located at the front of the machine and mounted directly to the hammer. The compression spring will have a longer life cycle and is much easier to adjust and replace. 3. Cantilevered adjustment mechanisms were added to aid in fine tuning the 3.2 mm gap between the hammer and anvil. 4. Cam followers were added to engage a vertical Vee block to reduce side wobble. 5. A second cam was added to the machine to further stabilize the table. The cam design was changed so they are replaceable. 6. A programmable controller was added to control the rpm of the cams to ?? ? rpm. A ""Hall Effect"" sensor provides feedback from the cam shaft to the controller to control shaft rotation. 7. The ""V"" belt and pulleys were replaced with a timing belt and cogged pulleys. This will prevent slippage. 8. The ? horsepower motor was replaced with a 1/3 horsepower DC motor. 9. The rear spring mounting frame was changed to a weldment with bolts on top for easy removal of the top bracket for spring replacement. 10. The rear springs have been detailed in their specifications to provide 1335 N force per spring when installed. 11. The hammers have been replaced with a solid block to reduce the force per square inch when striking the anvil which should result in less wear and longer calibration intervals. 12. A belt guard was added to improve safety. 13. The anvil was changed to a two-piece construction to make it easier to replace when necessary. The shape of the anvil is square@ which allows for rotation without replacement. 14. A fixture mounting plate was added to the top plate to aid in fixture mounting and to prevent the need to disassemble the machine if a different fixture mounting is needed. Tapped holes are provided for a combination of fixture mountings. A threaded hole is provided for the accelerometer mounting and for the calibration of the tension test. 15. A calibration frame has been specified along with the appropriate force gage and connections. This should improve accuracy when calibrating the machine. 16. The location of the accelerometer has been standardized and will improve output measurements. 17. A study of accelerations using various weights that included the fixture mounting plate@ the DUT@ and the test fixture showed that when the sum of these weights are between 13.5 kg and 27.0 kg@ the accelerations are not dampened. A survey of the SAE Heavy Duty Lighting Committee Members determined that 97% of all test fixtures plus the fixture mounting plate weigh less than 13.5 kg. This will require fixture designs that allow weights to be added or removed to meet the requirement. When larger devices are tested and a larger fixture mounting plate is required they should be kept within the 13.5 and 27.0 kg range 18. Zert fittings have been added to lubricate the cam followers mentioned in item number 1 and 3 above. 19. A detailed procedure has been added to the document for calibrating the machine. 20. The mounting base has been specified with a pressurized vibration isolation system so that all machines are mounted on bases with similar dampening characteristics. 21. A screw type mechanism was added for adjusting belt tension on the motor. 22. Three GO-NO-GO gages have been detailed in the document to aid in the calibration of the machine. 23. The cam design was studied and it was determined that when the hammer strikes the anvil the cam has rotated 14 degrees. The cam design from 1938 lifts the hammer after 225 degrees of rotation. The cam design used on the first round robin test lifted the hammer at 255 degrees. This required high accelerations to lift the hammer to 3.2 mm (.125 inch) or top dead center (TDC) on the cam. Tests showed that the high accelerations caused the hammer to travel higher than desired with the gap around 4.98 to 5.99 mm (.196 to .236 inch). We also found that from the time the hammer first strikes the anvil (approximately 14 degrees cam rotation) until it is lifted at 255 degrees the hammer bounces on the anvil resulting in uncontrolled data points (around 4 g's). A new cam was designed to lift the hammer after 30 to 60 degrees rotation of the cam and making a smooth transition up to TDC. Tests revealed that the hammer/anvil gap did not exceed .125 inch and the data points were contained in a narrow band. 24. The SAE Heavy Duty Lighting Committee has conducted two round robin tests on 6 machines tooled by 5 different companies and has determined that the new machines@ when properly calibrated@ will greatly reduce variations from machine to machine. Benchmark data collected from machines in 1974 showed 1900% variation between peak to peak g values (over 200% if the lowest and highest values are thrown out). The following chart provides the results of the second round robin tests conducted by the SAE HDLC task force. There is approximately 31% variation in the data (20% if the lowest and highest values are thrown out). When the improvements listed above are incorporated in the J577 vibration machine@ following the detailed specifications along with proper calibration and fixturing@ the test results from machine to machine will show a reduction in variations. Deviation from these specifications could affect repeatability of the test."