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).
Informational leaflet explaining the operation and principle of the Gallometer for measuring fuel consumption.
| Identifier | ExFiles\Box 33\5\ Scan033 | |
| Date | 28th November 1922 guessed | |
| HOW. These drawings show :- (a) The four positions of the handle which turns the tap at the bottom. (b) The internal construction of the Gallometer. (c) Four sectional views of the tap, which show the way the petrol flows, or is cut off, in each position. S—Petrol supply pipe. C—Carburettor pipe. G—Hole into Gallometer. (O) “Off” position in which all connections are cut off. (1) Petrol flows from supply to Carburettor and the Gallometer is cut off. The car runs normally, just as if no Gallometer were fitted. (2) Petrol continues to flow to the Carburettor, but also it flows through the hole G into the Gallometer. (3) Petrol supply cut off so that the Carburettor is now fed solely from the petrol with which the Gallometer was filled in (2). [Centre Panel] THE GALLOMETER (PATENTS APPLIED FOR) INDICATES “Miles per Gallon” ON ANY MOTOR VEHICLE. MEASUREMENT IS THE KEY TO ECONOMY. WHY. If, in running one mile a car consumes : ¼ gallon, consumption=4 miles per gallon ; ¹/₂₃ gallon, consumption=23 miles per gallon; and similarly for any other simple fraction. The principle of the Gallometer is that the petrol used in running one mile is measured and indicated as such a simple fraction; then, as explained, the lower figure of the fraction is “miles per gallon.” The Gallometer, applied to a car, is usually mounted inside, below the dash, within easy reach of the driver, and is a permanent fitting on the car. Normally, the handle will be at (1). To test, the Gallometer is first filled by turning the handle to (2) : a slight overflow at the top indicates when it is full. Then the handle is returned to (1) and the car continues as usual, but with the Gallometer now exactly full of petrol. When a milestone is passed, or the mileage figure on the speedometer clicks over, the handle is turned to (3), which causes the car to run solely on the petrol in the Gallometer. At the end of the mile the handle is turned through “off” to (1) which retains the remaining petrol until its level is observed, either while the car continues to run, or later. The consumption of petrol over the measured mile causes its level to fall until it comes into view on the scale. The mark at which it stops represents the fraction of a gallon which has been consumed, because there is ¹/₄₀ gallon above the 40 mark ; ¹/₂₅ gallon above the 25 mark; etc. In the illustration, the petrol level has fallen to the 32 mark, so that the consumption is 32 miles per gallon. | ||