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 performance, noise levels, and power loss of various silencer designs.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan199 | |
| Date | 26th November 1925 | |
| contd :- -2- are diverted owing to this method of spacing the baffles. SILENCER Silencer No.1. was found to be considerably quieter than standard but yet not sufficiently quiet. The exhaust forward note was rather pronounced, and whistling took place at from 38 - 46 m.p.h. Silencer No.2. fitted with three alternative baffles was considerably quieter than No.1. and no whistling took place. It was not considered sufficiently quiet however and owing to the very small extra loss in power it was decided to incorporate a fourth baffle in it, giving us :- Silencer lll. This was found to be quiet and free from whistling; the power losses as compared with the standard silencer are not considered excessive and quite compatible with the extra silence achieved. This silencer was approved by London Sales 26.11.25. POWER. The attached power curves show the road wheel B.HP. absorbed by the silencers under consideration. The curve for Silencer No.ll has been omitted; this followed very closely curve No.1. It will be observed that silencer No.lll. absorbs very little more B.HP. than the present standard, only 2 B.HP. more at 2000 r.p.m. These comparatively small extra losses are not noticeable on the road and cannot be detected on timed hill climbs or acceleration tests. contd :- | ||