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).
Causes and potential solutions for 'booming' noises in coachbuilt car bodies.
| Identifier | ExFiles\Box 14\5\ Scan162 | |
| Date | 21th May 1930 | |
| - 2 - EP{G. Eric Platford - Chief Quality Engineer}7/H21.5.30. The "dead" fabric type body is dying out in favour of the boomy coachbuilt type. We find the characteristics of the chassis for torque reaction affect and fuss etc. at high speeds in most cases entirely changed when bodies are fitted. We are tackling the body people to deal with bodies which have distinct tendencies to boom, set up by the roof, or large panels for the body, scuttle, or floorboards, or large wind-screens, and although these matters are given attention by the Coachbuilders, the trouble is not entirely eliminated. The "fuss, rumble, sting" and exhaust boom periods at high engine speeds are still troublesome on both chassis. As regards the boomy periods set up by the Exhaust, these do vary according to the sonorous condition of the body, in some are really objectionable. The slightest leak from the exhaust cutout and deep metal valances and covering on back of chassis we consider aggravate this. Similar large deep wings and even wheel discs, aggravate axle, tyre and other noises which we have proved out. We have several cases of complaint now in hand of 20 HP. boom period 50 m.p.h. (Considered exhaust), which as a chassis are quite normal but objectionable with body fitted. (Bodies now having coachbuilders attention owing to their tendency to boom.) This matter has been demonstrated to and is receiving the attention of the Experimental Dept. So far we have not found any improvement on the new high compression engine chassis. As a matter of fact, we take the view that this will be more objectionable owing to higher cruising speed which will be maintained with this chassis. Temporarily disconnecting entirely the centre support of subframe to chassis did not affect a general booming complaint on a Phantom II. This confirms the last paragraph in R's memo. We should like to try a car fitted with boomy body (enclosed front limousine - say Hoopers) and also the quietened exhaust and complete rubber insulated subframe, as mentioned in R's memo. We feel we ought to be in a position, retrospectively in such cases, to make some modification of the existing silencer, if it is considered such a modification can be applied and will avoid or alleviate the trouble. EP.{G. Eric Platford - Chief Quality Engineer} | ||