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).
Comparative test report on the Vokes-Blanvac exhaust silencer against a competitive model at various engine speeds.
| Identifier | ExFiles\Box 152\3\ scan0122 | |
| Date | 4th May 1938 guessed | |
| making provision for either silencer to be used whilst all engine controls remained fixed. Comparative tests were made at different engine speeds, as given below:- 150 r.p.m. slow running speed. The Vokes-Blanvac gave a more definite pulsation than the competitive pattern but by attaching the tail pipe this sound was softened down. 800 r.p.m. The Vokes-Blanvac sounded definitely better than the competitive pattern with no loss of power reading on the Dynamometer. 1,600 r.p.m. (30 m.p.h. road speed). The difference in sound between the two silencers became still more marked. The Vokes-Blanvac can be described as a soft hum in comparison with the competitive pattern loud rushing sound. No difference in power was shown by the Dynamometer. 2,000 and 2,500 r.p.m. (40 and 50 m.p.h. road speed). All the remarks applied to 1,600 r.p.m. still hold good at these increased speeds. Conclusion: FROM THE ABOVE TESTS IT APPEARS THAT THE VOKES-BLANVAC EXHAUST SILENCER, TAKEN GENERALLY, IS MUCH SUPERIOR TO THE COMPETITIVE PATTERN. (Signed)................. | ||