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).
Technical analysis and comparison of leakage effects in silent tappets for various engine models.
| Identifier | ExFiles\Box 17\6\ Scan290 | |
| Date | 24th July 1934 | |
| -2- Thus the effect of leakage is directly proportional to the square of the clearance and inversely to the cube of the plunger diameter. These quantities should be kept as small and as large as possible respectively. The formula emphasises the inherent disadvantage of the Halford type of tappet and the importance of maintaining k as low as possible in the G.M. type. The Phantom set of tappets have a value of k equal to 1/4 and the SpectreCodename for Phantom III equal to 1/6; thus, other quantities being equal the effect of leakage would be 2 1/4 times as great for the Phantom as for the SpectreCodename for Phantom III. Taking a constant clearance in the various cases of silent tappets we have tried; and assuming that L is proportional to the valve spring load with the valve closed, we have the following relative effects of leakage. | Engine | Type of Tappet | k | L | d | b | Relative Movement at rocker end | |---------|----------------|-----|----|------|------|---------------------------------| | Ph.II | G.M. | 1/4 | 70 | .625 | .900 | 20.0 | | J-III. | G.M. | 1/4 | 70 | .525 | .650 | 46.5 | | SpectreCodename for Phantom III | G.M. | 1/6 | 50 | .525 | .725 | 13.25 | | Bentley | H.{Arthur M. Hanbury - Head Complaints} | 1 | 56 | .500 | .500 | 896.0 | Hs{Lord Ernest Hives - Chair}/F.Ll.Smith. | ||