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).
Cure for a booming sound in cars by isolating the dash and steering column using rubber mounts.
| Identifier | ExFiles\Box 137\4\ scan0279 | |
| Date | 23th March 1931 | |
| TO HS.{Lord Ernest Hives - Chair} FROM EV.{Ivan Evernden - coachwork} COPY TO R.{Sir Henry Royce} SG.{Arthur F. Sidgreaves - MD} E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} X634 V2/23.3.31. RE BOOMING CARS. We understand you to say that the isolation of the dash and column from the frame effects a cure of the booming experienced at 60 MPH. We agree to "Rs{Sir Henry Royce's Secretary}" remark that it is not possible to mount the dashboard on rubber chiefly because we wish to use the dash as a frame crossmember and to take the torsion on the frame side member produced by a spare wheel carried at the side. It has occurred to us, however, that it might be possible to put a small amount of rubber isolation in the clip that supports the column from the dash . se sketch:- [Handwritten on left sketch] THIS IS NOW A RUBBER GLAND RUBBER .125 CLEARANCE .062 [Handwritten on right sketch] RUBBER SHAPED TO ALLOW IN & OUT PUMPING TO BE EFFECTIVE THE RUBBER NEED ONLY ALLOW OF SAY 90 THOU RADIAL MOVEMENT & THIS WOULD NOT BE APPRECIATED AT THE WHEEL We have tried to form the rubber so that it will permit the column to pump in and out of the support bracket without working the diaphram of the dash. We do feel that it is a case of resonance between the engine and the dash is acting as a diaphram amplifier. a good example of this is the stirling loud speaker which has a pare diaphram which is never resonant with any of the emitted notes. For this very reason damping will have little effect neither will stiffening the face of the dash. In the case of resonance, damping in a small degree is effective and stiffening or weakening a perfect cure. We suggest that the reaction on the column from the thrust on the pendulum lever willnot cause the column to pump in and out of the support bracket as the cast dash has bending stiffness fore and aft and is steadied at the top by the body through the scuttle isolation rubbers. EV.{Ivan Evernden - coachwork} | ||