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).
Modifications made to the Spectre Exhaust System to reduce horsepower loss.
| Identifier | ExFiles\Box 4\1\ 01-page237 | |
| Date | 29th January 1935 | |
| /300 To E.{Mr Elliott - Chief Engineer} cp to Mr. c. to Hy.{Tom Haldenby - Plant Engineer} Hs{Lord Ernest Hives - Chair}/Wym{G. Harold Whyman - Experimental Manager};28/KW.29.1.35. SpectreCodename for Phantom III Exhaust System. We have carried out a number of modifications to the above system with a view to reducing the H.P. loss, which in the original system was 54 B.H.P. at 2750 r.p.m., see memo. Hs{Lord Ernest Hives - Chair}/Bwdl.3/KW. 5.12.34. An analysis of the figures shows that the rear silencer was responsible for 40 B.H.P. loss, and our present modifications have been confined to this part of the system, with the result we have now reduced the rear silencer B.H.P. loss to 24. The following is a list of the alterations carried out - (1) Inlet cone small diam. increased from 1.375" to 2.00". (2) Further row of 10 5/16" dia. holes drilled round inlet cone. (3) Fishtail sawn off swan neck pipe. (4) Blank end sawn off main inner pipe. (5) 5/16" dia. holes in both top hats increased in number from 80 to 120. The fishtail noise is a little more noticeable but not objectionable, but we have run into light booms at 20-22 m.p.h., 30-31 m.p.h. and 40 m.p.h. To try and overcome these booms we have instructed for a larger front expansion chamber and an oval shaped swan neck pipe giving the same area as a round pipe, 3.00" dia. Both these additions should also help us for tail pipe noise and power loss. Hs{Lord Ernest Hives - Chair}/G.H.Wyman. | ||