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).
Eliminating body 'boom' by adjusting scuttles, engine feet, and other components on different body types.
| Identifier | Morton\M19\ img047 | |
| Date | 21th March 1931 | |
| - 4 - HS{Lord Ernest Hives - Chair}/HWS.3/KT.21.3.31.cont. chassis. However, as the following results shew, it would be quite possible to change a body from one chassis to another and unconsciously alter the conditions of mounting so that the boom was appreciably reduced. We find speaking generally that - (1) With Cabriolet de Ville bodies we can eliminate the boom by removing the rear engine feet. (2) Saloon bodies are liable to be more difficult but can frequently be cured by slacking off the scuttle isolation bolts in addition to removing the rear engine feet. (3) Limousines with partitions are the most difficult to deal with (25-EX). Raising the partition generally makes the boom at least 40% worse in the front seats. We have almost cured our worst example by isolating the column where it is attached to the dash, and isolating the scuttle from the angle bracket which carries the floorboards. It should be noted that tightening the scuttle isolation bolts is good for torque reaction but can increase booms. Naturally in changing the bodies over this feature might be altered as also the central window thereby confusing the results. As an instance of some of the problems that bodies create, 18.G.IV has a worse boom running over tram sets at 30 M.P.H. with engine stopped, than it has at any speed on an ordinary road with the engine mounted solid, and driving the car normally. Again we have 25-EX whose body booms persistently with an ordinary chassis though lifted several inches clear of the frame and dashboard by a crane. We agree that since the car reaches the customer complete, it is useless to throw all the responsibility onto the coachbuilder, the position is equally hopeless if the problem is left to the chassis maker entirely. Answering the questions on Page 3. of your memo. (1) We believe that P.II booms are worse than P.I for the reasons given. We are still trying to find other reasons connected with the chassis. (2) We think bodies today have greater booming tendencies than previously. | ||