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 engineering merits and installation of an equalizer bell and line for petrol gauges.
| Identifier | ExFiles\Box 44\2\ Scan172 | |
| Date | 12th July 1928 | |
| Messrs.Rolls-Royce,Ltd., Date 12. 7. 28. Page 2 top of the tank where it is connected to an equalizer bell, which is sealed by the petrol on its rising above the last gallon of calibration. The equalizer bell and line have hitherto only been used by the King-Seeley Corporation and ourselves on our industrial gauges, aeroplane installations and installations in which the tank unit and filler of the petrol tank are enclosed within the bonnet of a car, where pressure above atmospheric exists in relation to the atmospheric pressure at the dash-board where the gauge is situated. [handwritten above 'dash-board': facia] From an engineering point of view, we believe you will appreciate the merits of this suggested installation in your case. The reading in which you are interested is only that of the calibrated portion of the tank. Therefore when this point is passed, the head imposed by the height of the filler and any unusual pressures which may be exerted thereon will be dealt with by equalizing the pressure on the top of the gauge, even up to the limit of pressure that the joints in the system will withstand. From an installation point of view, we have found that this pressure balance or equalizer line does not present any difficulties. The two small copper pipes are led within a flexible armoured pipe, or at a certain point where preferred, such as between the back of the chassis and the tank connections | ||