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).
Report comparing Vokes-Blanvac exhaust silencers against competitor and manufacturer models, detailing back pressures at various RPMs.
| Identifier | ExFiles\Box 152\3\ scan0123 | |
| Date | 4th May 1938 | |
| 4th May, 1938. REPORT ON VOKES-BLANVAC EXHAUST SILENCER ----------------------------- on high class fast Passenger Car test carried out by Manufacturers. "A" "B" "C" "D" latest Manufacturer's Vokes No.2. Vokes No.3. P.M. competitive special silent to compete with to compete with type.Sports pattern for type B. type A.{Mr Adams} Model Saloon models. 1500 4.95 6.7 6.2 4.7 2000 3.8 5.2 4.8 3.6 2500 2.9 3.9 3.5 2.7 3000 1.5 2.8 2.4 1.8 3500 - 2.1 1.6 1.3 4000 - 1.6 1.3 1.0. THE ABOVE TABLE SHOWS THE BACK PRESSURES IN INCHES OF MERCURY OF EXHAUST SILENCERS AT VARIOUS R.P.M. Vokes No.2. Silencer, same as the Manufacturer's best for silence, (if anything Vokes slightly better). Vokes No.3. Silencer gave a deep note, not increasing after 2500 r.p.m. About same as competitive Silencer. Over 3000 r.p.m. Vokes No.3. showed an improvement on competitive pattern, less back pressure due to utilisation of exhaust gas energy to produce depression or vacuum. Absolutely no tinny or drumming noise from body of Silencer, or running down noise. ---o0o--- | ||