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).
Experiments and methods for noise insulation in Bentley cars using felt.
| Identifier | ExFiles\Box 138\1\ scan0136 | |
| Date | 14th March 1935 | |
| To Sg.{Arthur F. Sidgreaves - MD} c. to Wor.{Arthur Wormald - General Works Manager} c. to C. c. to E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to Hn.{F. C. Honeyman - Retail orders} c. to Bn.{W.O. Bentley / Mr Barrington} Re Noise Insulation. We have carried out a number of experiments on No.1 and No.4 Bentley cars with a view to preventing the mechanical noises in the engine, tappets, etc., and exhaust noises, from being heard in the body, and have now obtained very satisfactory results. The method we employed was the liberal use of felt on the dashboard, scuttle, floorboards and rear luggage boot, and a sheet metal shield coated with felt underneath the rear seat. The fitting of this material to the above mentioned 2 cars has resulted in them both being infinitely nicer cars to drive; in fact it has transformed them from mechanically noisy cars to mechanically quiet cars. The reason we use the word mechanically is so that it will not be confused with the "boom" periods prevalent in the Bentley car, because although our felting scheme has a "deadening" effect on booms, it does not eliminate them. The scheme in detail is as follows :- (a) The dashboard must be insulated with felt 1/2" thick, reinforced on the outside by a layer of fibre sheeting, to be secured to the dashboard with 3/32" split pins and plain washers. (b) All floorboards must be bedded on felt or baize and all joints should be felt lined. (c) The front floorboards should be covered with a layer of felt 1/2" thick, attached by adhesive to a rubber sheet .062" thick, in the form of a mat. In the case of metal front floorboards, these should be lined with felt 1/4" thick stuck on with adhesive in addition to the above. (d) The pedal plate on existing cars should be lined with felt 1/4" thick, fitted tightly round the pedal stems, and stuck on with adhesive, but for future cars we ought to arrange for large circular felt pads around the pedal stems, held up to the bottom side of the plate by springs, effectively sealing up the holes through which the pedal stems operate in all positions of the pedals. | ||