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 design and function of a magnetic petrol gauge, clipped from 'Motor' magazine.
| Identifier | ExFiles\Box 75\2\ scan0117 | |
| Date | 17th March 1914 | |
| R.R. 235A (150 H) (S.A. 209. 25-1-15) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 0900. 7984 Motor 17:3:14 A MAGNETIC PETROL GAUGE. A very general form of petrol gauge for showing the amount of petrol which may be at any time in the tank is that in which a float of cork or hollow metal is arranged within a tube fitted inside the petrol tank in such a way that, as it rises within the tube, is caused to revolve by means of spiral guides in the sides of the tube, or else to cause a central rod to revolve by a spiral guide within the float, in either case the amount of rotary movement being communicated to an indicator working over the face of a dial at the top of the tube and on the outside of the tank. This construction has, of course, necessitated there being a central aperture in the dial through which the rod operating the indicating finger can pass, and this central aperture, small as it is, has always been a source of loss of petrol by evaporations, perhaps not a large one, truly, but still a loss, and an American firm, the Boston Auto-Garage Co., of Boston, U.S.A., has recognized this drawback, and has remedied it by magnetic means. Relying upon the usual method of employing a tube, a float and a spiral slot or guide, in order to obtain a rotary movement, they do not pierce the dial plate at all, but mount beneath it and upon the top of the operating rod a permanent magnet, which has the effect of causing a needle on the top of the dial—and hence outside the tank—to follow its movements and synchronize with it, thus giving the same result upon the dial as if the indicator had been directly connected with the mechanism inside. Another method of operating the gauge is by dispensing with the tube and guides and mounting the float on the end of a cranked arm, which, in rising, turns a rod carrying the magnet horizontally, an arrangement which allows the gauge to be fitted to the end or side of the tank. The annexed illustration shows several ways in which the device has been worked out. Key to diagram. (1) "Triumph" dash gauge. (1a) Petrol supply tube from T joint to gauge. (1b) Tube from tank to T joint. (1c) T joint. (1d) Connection to carburetter. (2) No. 36 upright gauge, shown in section. (3) Gauge, applied to side of tank. (3a) Gauge, shown in section, applied to dome end of tank. (4) Locker, motor boat or storage gauges. (S) Stand-pipe from tank to reading level; any length. (5) No. 2 upright gauge. (B) Flange bushing. | ||