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 from H.M. Hobson Ltd. regarding an investigation into why recording fluid in a Hobson K-S Telegage is turning black.
| Identifier | ExFiles\Box 61\3\ scan0143 | |
| Date | 16th December 1930 | |
| COPY From: H.M.HOBSON LTD. 47-58, The Vale Acton London W.3. 16th December 1930 TPS/MW ROY{Sir Henry Royce}/JT/HP. Messrs. Rolls-Royce Ltd. Derby Dear Sirs, With further reference to the information which we recently transmitted to you, with regard to the cause of the recording fluid in the Hobson K-S Telegage turning black, this occurrence has been traced in another instance to a piece of the braiding wire from the electric lighting cable being introduced into the brass back tube of the instrument. The matter is now under investigation at the Imperial College of Science, London, and the action has been proved up to a point, namely, that the white metal braiding wire used in the lighting cables on certain motor car installations, if introduced into the back tube in the presence of Tetrabromide, brass, and copper shims, within 24 hours turns the liquid both in the back tube and front glass completely black, and other actions ensue. If, however, this action is attempted to be started in an ordinary glass test tube, with the same ingredients present, the phenomenon does not occur. It is therefore expected that some electrolytic or other action is required in addition to set this action in motion. It was quite clearly proved in the first instance, where a piece of this wire was found inserted in the back tube, as to what the original cause of the trouble was, as the operatives installing the gauges on the assembly line were subsequently watched, and it was found that two of them at any rate were using this type of wire for extracting small quantities of liquid from the gauge, for the purpose of setting the zero levels on the assembly line. Since the provision of a wooden dip stick or a pipe cleaner for the purpose of extracting small drops of liquid to set the zero level, no case of a similar nature has been reported from the manufacturers in question. (Continued) ENCLOSURE Nº 960 "JUSTSO" | ||