From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Tests conducted on J.III type shock dampers using an N.S. 3497 conical seated valve.
| Identifier | ExFiles\Box 105\3\ scan0280 | |
| Date | 18th October 1932 | |
| 5520. FILES ONLY N.S. 3405. J.III. TYPE SHOCK DAMPERS. 18.10.32. Tests with N.S. 3497 Conical Seated Valve. This type of valve as originally designed had a narrow brimmed (.100" wide) valve damping 'hat' attached. With this attachment it was possible, providing the 'hat' was working in oil - not dry - to overcome the 'squawk' which had previously caused considerable trouble. There was, however, a tendency for the valve to "thump", and in addition to this another trouble arose. After statically setting the ball pin load to 90 lbs. L.P. running the damper until a temperature of approx. 80°C was attained (the static load was then normal) and then cooling off, it was found that the initial static load had increased to between 130 and 150 lbs. L.P. The H.P. loads were not readily obtainable with the damper on the rig. This was thought to be due to the fact that, when initially filled, the oil had not had time to penetrate to the 'hat'. When heated up the oil perculated into the 'hat' chamber and thus when cooled the 'hat' had to overcome the resistance on the cold oil. Various 'hat' clearances, atmospheric inlet holes, drilled studs, cylinder grooves, etc, were tried. At this stage diagrams were taken of both high and low pressures, at various temperatures with .005" diametral clearance, and a .105" atmospheric inlet hole. It was then found that whereas the high pressure tended to decrease the low pressure increased, as the oil temperature increased and the diagrams returned to normal levels when the damper was again cooled off. This was contrary to the static load variation experienced. Four inch stroke was used to give greatest range of diagrams and speeds. It was decided to lengthen the brim of the hat to .250" It was eventually found that the best compromise between the three troubles experienced (i.e. squawk, knock, and building up) was obtained with this type of 'hat' having .005" diametral clearance, and two holes .055" diameter drilled in the wall. Or alternatively, with .032" diameter hole in the L.P. face of the valve (to ensure oil being supplied to the 'hat' chamber), .015" diametral 'hat' clearance, and two .093" holes in the wall. In both cases quoted the atmospheric inlet hole | ||