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).
The description and testing of self-adjusting tappets supplied by Self-Adjusting Tappets Ltd.
| Identifier | ExFiles\Box 17\6\ Scan172 | |
| Date | 31th January 1934 | |
| To Sg.{Arthur F. Sidgreaves - MD} from Hs{Lord Ernest Hives - Chair}/Std. c. to WoR.{Arthur Wormald - General Works Manager} c. to Ng. c. to E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} x7060 Hs{Lord Ernest Hives - Chair}/Std.10/KW.31.1.34. Report on Self-Adjusting Tappets supplied to us by Self-Adjusting Tappets Ltd. --------------------------------- DESCRIPTION. The method of self-adjustment of this type of tappet is shown in accompanying sketch - a coarse square thread on the end of the push rod A engages with a similar thread in the cap B. An external cap C, transmits the rocker load to cap B. via the ball shown, and ensures that the cap B. is free to rotate. Cap B. is linked to a helical spring D.{John DeLooze - Company Secretary} (see diagram) which opposes right-handed motion of the screw thread, and so avoids all clearance when the valve is closed. When the push rod load comes on the thread, as valve is opening or closing, the inefficiency of friction does not allow movement between the male and female parts of the thread during the opening period, and hence no valve lift is lost. Should a condition be obtained however in which the valve is held off its seat, the continued load coupled with vibration will cause the thread to rotate slowly until the valve is closed. TESTS. Six of the push rods, as received by us, were fitted to 22-EX car and five of these functioned correctly - they did not hold the valves off their seats when engine was running and caused no noise whatsoever. The sixth rod persisted in opening the valve and holding it open - examination of the mechanism of the adjusting end of the rod failed to reveal any cause for this. Accordingly the remaining eleven rods were then fitted to 22-EX and run for approximately 100 miles at high engine revolutions. All the rods functioned correctly, and the only criticism directed against them is that after bringing the car in with the engine hot and leaving until next morning, some of the valves were found | ||