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).
Letter to John Marston Ltd. concerning the failure of an 'F' type oil cooler and suggesting changes to the manufacturing process.
| Identifier | ExFiles\Box 150\2\ scan0035 | |
| Date | 24th May 1938 | |
| 1280 EXPERIMENTAL DEPT. RM {William Robotham - Chief Engineer} /Std.2/JH. 24th May, 1938. Messrs. John Marston Ltd., WOLVERHAMPTON. For the attention of Mr. Dunn. Dear Sirs, Confirming our telephone conversation on Friday with your Mr. Smith, we would point out that B.II Dummy shutter sets are urgently required for production and we are still awaiting a satisfactory proof set. We have now failed an 'F' type oil cooler on an experimental engine which we have been running continuously and examination of the fractured portion (at the centre of the edge of the bottom plate for a distance of about five tubes) indicates that the solder band has parted gradually and the edges of the fracture have been rubbed smooth by vibration of the plate and tubes. While the depth of soldering is entirely satisfactory there are a number of air bubbles in the solder which may have contributed to the reason for the failure and we are anxious to ensure that these blow-holes do not occur in future coolers. It seems very likely that they are due to air being trapped in the spaces between the tubes bulges when the cooler is dipped and we suggest that a means of avoiding this is to individually dip the end bulges of each tube into flux during the process of the tubes into the case - the flux would thus be retained by capillary attraction and prevent trapping of air when the cooler is dipped. It would be necessary of course to wash the cooler out very thoroughly after dipping and our Laboratory state that the most satisfactory way of doing this is to rinse cooler internally with a weak solution (5% = ½ lb. to 1 gallon water) of ammonium chloride and then well wash out with hot fresh water. If possible we would like you to build any future coolers in this manner, since it is obviously essential to take every possible precaution to prevent failure occurring. | ||