18.104.22.168 Buffer Tests
(a) three drop tests with a total test weight equal to the manufacturer's rated maximum load for which the porting is designed [see 22.214.171.124(a)]
(b) one drop test with a total test weight equal to the manufacturer's rated minimum load for which the porting is designed (see 126.96.36.199)
Following each drop test, the buffer shall be held in its fully compressed position for a period of 5 min, and shall then be allowed to return freely to its fully extended position and stand for 30 min to permit return of the oil to the reservoir and to permit escape of any air entrained in the oil.
On each of these tests, the average retardation of the test weight, during the stroke of the buffer, shall not exceed 9.81 m/s2 (32.2 ft/s2), and any retardation peak having a duration of more than 0.04 s shall not exceed 24.5 m/s2 (80.5 ft/s2).
On completion of the drop tests, no part of the buffer shall show any permanent deformation or injury.
(a) Two drop tests shall be made as follows:
(1) One drop test shall be made with the porting as specified in 188.8.131.52(a), with a total test weight equal to 120% of the manufacturer's rated maximum load, from a height such that the maximum velocity attained by the falling weight during the buffer compression shall be equal to 125% of the rated car speed for which the buffer is rated. In this test, the retardation shall be noted and shall be permitted to exceed the values specified in 184.108.40.206.1.
Immediately following this test, the buffer shall be examined externally for visible deformation or injury. If no damage is apparent, the buffer shall then be fully compressed at low speed and then released to determine if it will return freely to its extended position.
(2) After the buffer has been examined externally and has returned freely to its extended position, a second drop test shall be made from the same height and with the same load as specified in 220.127.116.11.1(a). During this test, the retardation shall not exceed the corresponding retardation developed in the test specified in 18.104.22.168.1(a) by more than 5%.
(b) If, for a given stroke of a buffer having more than one porting, the construction of the buffer varies for the different portings, then a strength test similar to that specified in (a)(1) shall also be made for the porting having the range at minimum loads for which the porting is designed as specified in 22.214.171.124(b).
Following each drop test, the buffer shall be held in its fully compressed position for a period of 5 min, and shall then be allowed to freely return to its fully extended position and stand for 30 min to permit return of the oil to the reservoir and to permit the escape of any air entrained in the oil.
The drop in oil level, as indicated by these measurements, shall show no loss of oil exceeding 5 mm/m (0.06 in./ft) of buffer stroke, but in no case shall the loss be that the oil level is below the bottom of the plunger or the highest metering orifice, whichever is higher.
Where the volume of oil above the porting is small when the buffer is filled to its normal working level, the laboratory shall be permitted to make additional tests for oil leakage.
Should the plunger fail to return to its fully extended position or should the time required for it to return to its fully extended position exceed the time specified, the manufacturer shall either submit a duplicate buffer or install a new pressure cylinder and piston, following which the plunger-return test shall be repeated. Should the buffer again fail to meet the plunger-return test requirements, it shall be rejected.
Buffers of the spring-return type shall be tested for plunger return with a 20 kg (45 lb) test weight resting on top of the plunger during the test. The plunger shall be depressed 50 mm (2 in.), and, when released, the plunger, while supporting the test weight, shall return to its fully extended position within 30 s.
(a) Spring-Return-Type Buffers. The lateral movement at the top of the fully extended plunger shall be accurately measured, the upper end of the plunger being manually moved from its extreme right to its extreme left position. One-half of the total movement measured shall be considered as being the true lateral movement at the top of the plunger and shall not exceed 5 mm/m (0.06 in./ft) of buffer stroke.
(b) Gravity-Return-Type Buffers. A similar test for lateral movement shall be made. The measurement shall be taken at the lower end of the buffer cylinder when the buffer plunger is fully extended and braced to prevent lateral movement. One-half of the total movement measured shall not exceed 5 mm/m (0.06 in./ft) of buffer stroke.