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).
Operation sheet for the Hobson K-S Telegage fuel gauge system.
| Identifier | ExFiles\Box 44\4\ Scan110 | |
| Date | 13th March 1930 guessed | |
| BRITISH MADE Operation Sheet FOR THE HOBSON K-S TELEGAGE Telegrams: "ASSEMBLAGE, LONDON." Telephone: CHISWICK 4231 (4 lines). MADE BY H.{Arthur M. Hanbury - Head Complaints} M.{Mr Moon / Mr Moore} HOBSON LIMITED 47/55, THE VALE, ACTON, LONDON, W. 3. The Hobson K-S Telegage consists of three units—the Head, Tank Unit and Air Line. In operating condition the Air Tube and Air Chamber of the Tank Unit and the Air Line connecting the Tank Unit to the Head are filled with air. (See Figures 3 and 4). The petrol tries to rise to the same level in the Tank Unit as it is in the tank. This is not possible because of the air trapped between the bottom of the Tank Unit and the Liquid in the Head. However, the effort of the petrol to get into the Air Chamber presses on the trapped air and this pressure is communicated through the Air Tube and Air Line to the Head on the Instrument board, where it is recorded by the rise of the red Liquid in the Glass Tube. THE TANK UNIT, Fig. 1, shows the Air Tube and Air Chamber which must always be filled with air. The petrol tries to enter through Hole "C," and thus presses on the trapped air. This is the only part of the Tank Unit that has anything to do with the reading of the Gauge. The Vent Tube, open at the top, is merely a safety device, which protects the gauge against high pressure. It does not enter into the operation of the gauge in any way. The remainder of the Tank Unit, that is, the Air Cup and Air Delivery Tube, act only as a means of supplying fresh air to the Air Chamber. This is to overcome the loss of air due to absorption in the petrol and contraction of the air due to a sudden drop of temperature. The Air Supply mentioned above is obtained by utilising the movement of petrol in the Tank. When the Air Cup is above the level of the petrol it is constantly being filled by the surge and splash when the car is in motion. This petrol runs through the Drain Hole 'D' and down the Air Delivery Tube drawing with it a few bubbles of air. At the bottom of the tube the air bubbles out and rises under the Air Chamber. It enters the Air Chamber through Hole "C" and replaces any petrol which may be there. When the Air Chamber is full of air these bubbles simply pass off and are not used. THE HEAD, shown in Fig. 2, is mounted on the Instrument Board and is simply a U-tube containing a special heavy red liquid. The front half of the U-tube is a Glass Tube open at the top and the back half is a Brass Tube. A U-tube containing liquid is the most accurate instrument known for measuring pressure. THE AIR LINE, coming from the Tank Unit, is connected at the top of the Brass Tube. Any pressure which comes through the Air Line will press the liquid downward in the Brass Tube and upward in the Glass Tube. In fact, the difference in levels of the liquid in the two tubes is an exact measurement of the pressure coming through the Air Line and hence records the depth of petrol in the tank. By calibrating the gauge in gallons an EXACT reading in gallons is shown on the instrument board. Three things are necessary to ensure the Gauge functioning correctly:— 1. The Red Liquid in the Head must be set at the bottom line when disconnected and hold this setting. If the Head shows a leak and will not hold setting, it should be returned for replacement. 2. The Air System Must Be Free from Leaks or Obstructions. The most common obstruction is petrol which, however, CAN ONLY BE DRIVEN INTO THE AIR LINE WHEN THERE IS A LEAK OR CONNECTIONS ARE NOT PROPERLY MADE. Petrol being a moving obstruction, will cause a very erratic reading of the Gauge. 3. The Tank Unit Must Supply Air by the surging of the petrol, as described above. When you have these three conditions and the gauge is reconnected the Liquid in the Head will start to rise after the car has been driven and will continue to rise until it records the true contents of the tank. Stopping, starting and turning of corners will hasten this action. After this the gauge will not again lose its reading unless disconnected. LIQUID: Hobson K-S Liquid is specially selected because of its specific gravity and other characteristics. POSITIVELY NO OTHER WILL DO. Every distributor and dealer should have a bottle of Hobson K-S Liquid to cover emergencies. These bottles can be ordered in various sizes as follows: No. 1 Bottle, ½ oz., sufficient for filling 3 gauges No. 1½ Bottle, 1 oz., sufficient for filling 20 gauges No. 2 Bottle, 2 oz., sufficient for filling 40 gauges No. 3 Bottle, 6 oz., sufficient for filling 125 gauges RESERVE: The Telegage provides a reserve of somewhat less than one gallon, and this amount is not recorded on the gauge, as the reading starts at Hole "C." Above this point the gauge registers exactly, gallon for gallon, all petrol put into the tank. (THIS IS NOT THE CORRECTION SHEET.) | ||