Material options and design changes for the Wraith III exhaust silencer to improve durability.
| Identifier | ExFiles\Box 8\8\ 08-page62 | |
| Date | 15th September 1938 | |
| 623 DA. {Bernard Day - Chassis Design} 1/G.15.9.38. WRAITH III. EXHAUST SYSTEM. In view of the condition of the modified silencer interior parts taken from the Wraith lll car after 2,600 miles running, we are holding back the designs which we have made of this type of exhaust silencer, as the material used in the experimental system is obviously not satisfactory, the perforated tubes which are made from sheet mild steel .032" thick being badly flaked. The maximum thickness of the mild steel plate which can be used with the recommended diameter of balancing holes punched in the material is .040", and this would not have a very long life, the holes at present are .093" diameter. There are three methods of reducing the metal deterioration for the silencer internal parts - (1). By altering the material to Staybrite steel. In order to use a reasonable thickness of material in Staybrite, and to avoid drilling the balance holes, it will be necessary to increase the diameter of the holes to a minimum of .1875"; this, of course, means experimenting to find the number and position of the larger holes for correct tuning; there is also the question of the cost of Staybrite. (2). By increasing the thickness of the Mild Steel material to give a satisfactory length of life. This again means that in order to be able to punch the balance holes for tubes, it will be necessary to increase the diameter of the holes in relation to the thickness of metal used, and experiments are required to determine these points. There will certainly be a considerable increase in the weight of the silencer by this method. (3). By using the system in its present form with the silencer treated inside and outside with a protecting process such as the Follsain Penetral H.T. process. (4). We understand there is the possibility of a heat resisting steel being found, which would enable .040 thickness to be used, but so far we have not been able to get any particulars. If it is found essential to use the balance holes already tried on the experimental cars, with either items (1) or (2), it would mean that the holes would have to be drilled in the materials instead of punching, and this | ||
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).