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).
Use of rubber isolation on the dash column to resolve a booming issue in cars at 60 MPH.
| Identifier | WestWitteringFiles\V\March1931-September1931\ Scan076 | |
| Date | 23th March 1931 | |
| TO HS.{Lord Ernest Hives - Chair} FROM EV.{Ivan Evernden - coachwork} L.H.S.{Lord Herbert Scott - Chair} 112 G.N ORIGINAL COPY TO SG.{Arthur F. Sidgreaves - MD} DA.{Bernard Day - Chassis Design} RE BOOMING CARS. X6341 We understand you to say that the isolation of the dash 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. See sketch:- [Sketch with Annotations] THIS IS NOW A RUBBER GLAND. Rubber .125 Clearance .052 RUBBER SHAPED TO ALLOW IN & OUT PUMPING. TO BE EFFECTIVE THIS RUBBER NEED ONLY ALLOW OF SAY 20 THOUS RADIAL MOVEMENT, AND THIS WOULD NOT BE APPRECIATED AT THE WHEEL. We have tried to form the rubber so that it will pump in and out of the support bracket without working the diaphram of the dash. We do not feel that it is a case of resonance between the engine and the dash but that the dash is acting as a diaphram amplifier. A good example of this is the Sterling Loud Speaker which has a paper 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 will not 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. Agreed to H.B.B. EV.{Ivan Evernden - coachwork} | ||