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).
The principle and function of an O.S. Rear Tank Gauge.
| Identifier | ExFiles\Box 75\2\ scan0192 | |
| Date | 12th February 1927 guessed | |
| O.S. SPEEDOMETER CO. LTD. CONTINUATION SHEET NO. O.S. REAR TANK GAUGE. M <- Manometer <- Autovac Exhauster T.... ....E S ----C PRINCIPLE. To measure the pressure of the air necessary to balance the pressure of the liquid at the bottom of the tank. This pressure is equal to the height of the liquid and consequently proportional to the quantity that has to measured. DESCRIPTION of the GAUGE. This result is easily arrived at by joining a small bell C placed at the bottom of the tank to a manometer M by means of an airtight tube "E". Supposing the tank is empty, the air contained in the system bell-tube-manometer will be at atmospheric pressure. If at this moment petrol is poured in, the level of this rising, will tend to penetrate into the bell C but the air contained in the instrument being unable to escape, will be compressed in opposing the entrance of the liquid in the bell; its pressure therefore will be equal to the pressure of the petrol at the bottom of the tank. DESCRIPTION OF THE RENEWAL. But the compressed air contained in the instrument dissolves on coming into contact with a volatile liquid like petrol; further small leakages can allow the air to escape. It is therefore | ||