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).
Continuation sheet to AC-Sphinx discussing material stress tests, filter mounting, and leak-proofing solutions.
| Identifier | ExFiles\Box 135\3\ scan0266 | |
| Date | 6th April 1938 guessed | |
| THE AC-SPHINX SPARKING PLUG Co., LTD. CONTINUATION SHEET No. 2. been due to some impurity in the sheet, and you will be interested to know that when this half pressing was put on to an expanding tool under a press the split did not continue until considerable pressure was applied, and then did not continue along the same line but split out sideways from the end of the crack before continuing to split downwards, which seems to show quite definitely that this was caused by some inclusion in the metal, and was not in the nature of a crack due to it being over stressed. As a matter of fact a large number of pressings taken at random in the Press Shop were put on to an expanding tool, and in most instances the diameter of the mouth of the pressing was directly stretched to between 5/8" and 3/4" larger diameter than normal before any split took place, and in no case did a pressing split open until the diameter was increased by 1/2". We should be interested to see the other case which came to light as soon as you have finished with it, and we would then be interested in examining this carefully to see whether or not the same sort of trouble has occurred, or whether it has been due to wear between the pressing and the clip. As regards the mounting of the Filter, we would have imagined that a piece of strip fibre would probably have been a little more suitable than felt, where there is, as you mention, a possibility of movement of the Filter affecting the connection pipes. At the same time we would like to agree with you in your suggestion that the clip should be moved further away from the seam, as we think that there is some danger of compression of the case close to the seam affecting its leak-proof qualities. As regards your criticism that you had some difficulty in making a leak-proof joint between your aluminium washer and the face of the Filter, you will agree of course that as this is only sheet metal it certainly does not present anything like as perfect a face as one would get from a machined surface, and it may be necessary for us to lightly linish the ends to help in this jointing, though it has occurred to the writer that it might be useful to dip the aluminium washers in an oil proof adhesive before tightening up and in this connection we would propose to experiment with a cement known as Bostik, which we believe would be suitable for the purpose. In any case we will take the necessary precautions to avoid having any word marking at the point where we expect to make a sealed face. | ||