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 H.M. Hobson Ltd. discussing the design and safety features of a vent pipe for petrol tanks.
| Identifier | ExFiles\Box 44\2\ Scan091 | |
| Date | 10th November 1927 guessed | |
| COPY. Messrs. H.M.Hobson Ltd., 47-55 Acton Vale, London W.3. Messrs. Rolls-Royce Ltd., Derby. Dear Sirs, For the attention of Mr. W.A.Robotham. We beg to thank you for yours of the 7th.Nov. with reference to the vent pipe on Hobson K-S Telegages. We fully appreciate that your tanks are efficiently ventilated to atmosphere, but our vent pipe is in the nature of a safety device on our gauge, and prevents the liquid being blown out of the dashboard instrument, under practically all conditions. The vent pipe communicates directly with the upper chamberof the bottom bell. We are enclosing our diagram sheet, which shows exactly its position. This upper chamber communicates (1) with the gauge via the air tube and air line (2) with the petrol tank via the small holes B. and C. It is possible to put an abnormally high pressure on the whole of the petrol tank without blowing liquid out of the dashboard gauge, as the vent tube, which exhausts direct to atmosphere, allows the petrol, and so the pressure, to escape from the top half of the bottom bell, thus imposing on the gauge no higher head than the height of the top of this vent tube. Cases have been known where the end of the pipe nozzle, at a Filling Station, has been wrapped round with rag, and jammed into side fillers, making a practically air-tight joint. Anything up to a 6 ft. head may be imposed on the petrol in the tank under these conditions. It is really to deal with such cases, amongst others, that the vent tube safety feature must be retained. We fully realise the necessity for cleaning the job generally with regard to external pipes etc., and it occurs to us it would be possible for you to design a neat and efficient central fitting for your tank. This central fitting to form the base or body to carry the two tubes of our tank unit. It could also form the vent to the tank, and if brought high enough up would not cause any trouble with spilling. The entry of water could be obviated by a dome shape cowl, and if you thought fit, the petrol feed service could also be carried and taken from this body. contd :- | ||