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 speed at which resonance occurs in a spring system due to camshaft vibration.
| Identifier | ExFiles\Box 56\2\ Scan067 | |
| Date | 20th February 1929 guessed | |
| (4) SPEED AT WHICH RESONANCE OCCURS. Contemporary writers on this subject are agreed that the rate of forced vibration imposed by the camshaft sets up a state of resonance in the spring, which resonance becomes more intense when the natural frequency of the spring is an exact multiple of the RPM. of the camshaft. For example if the natural frequency of the spring is 10,000 vibrations per minute then the camshaft will synchronise at various speeds such as - 10,000 ÷ 10 vib: per rev. = 1000 RPM. of camshaft. " ÷ 12 " " " = 833 " " " ÷ 13 " " " = 769 " " " ÷ 14 " " " = 713 " " " ÷ 15 " " " = 667 " " etc. This does not explain however why we experience one very severe period at 1250 engine revs. with SS.{S. Smith} double springs, and no other apparent periods between 0 and bouncing speed -e.g.2700. It is somewhat significant that the lower period occurs at approximately half the bouncing speed, coupled with the fact that the latter appears to be another period of resonance coming on before the natural bouncing should occur. It appears to us that the nature of the forced vibration imposed by the camshaft is not so simple as has been assumed. The heavy acceleration and deceleration of the cam form are in effect two short sharp jabs at the valve spring of the same sign, occurring consecutively every revolution of the camshaft. The inlet valve lift cam LeC. 2558. originally employed on SS.{S. Smith} shews these impulses occurring at intervals of 92° and 268°. Reducing these figures to the simplest proportion we get 23 to 67, or say 1 to 3. | ||