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 development of the Phantom III exhaust system, addressing noise issues and material changes for cost savings.
| Identifier | ExFiles\Box 93\1\ scan0086 | |
| Date | 20th January 1937 | |
| To E.{Mr Elliott - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Whym. c. to Hs.{Lord Ernest Hives - Chair} cc to By.{R.W. Bailey - Chief Engineer} 323 Rm{William Robotham - Chief Engineer}/Whym.6/AP.20.1.37. PHANTOM III. EXHAUST SYSTEM. Continuing our previous report on Phantom III. exhaust systems, we have now had the opportunity of building up and testing three more silencers to our new design, and whilst they are all satisfactory on 37-EX, the car on which the original system was developed, they are hardly good enough on the other cars we have tried them on. This is certainly unfortunate, but it is very difficult to pick out the right car to work on, 37-EX. is an absolutely standard car, with the type of body which usually shews up exhaust booms, and one expected that a quiet system on this car would be even better on the Limousine type of body, but such is not the case. We are rather inclined to the opinion that the fault lies in the straight through system, and that one long continuous length of pipe might tune out a certain note perfectly, but any variation caused by carburation or distribution, turbulence or half a tooth in valve timing etc, is sufficient to produce a note slightly out of phase with the silencer tuning, and thus spoil the whole job. We have also tried this system on a car fitted with a four port head, and this again alters the characteristics of the system. We are therefore, for the timebeing, continuing with our present form of rear silencer, and carry on developing our new system to suit the four port head, which we understand will shortly be put into production. We are, however, hoping to standardise "Aluminized" mild steel in place of Staybright parts if 35-EX. goes through its 15,000 miles test satisfactorily, and this will mean a saving of approximately £5. 0. 0. per car. We are now saving approximately £1. 18. 0. by using nickel plated mild steel lagging covers in place of the stainless ones. Rm{William Robotham - Chief Engineer}/Whym. | ||