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\ Scan107 | |
| Date | 1st February 1930 guessed | |
| BRITISH MADE Operation Sheet (3) FOR THE HOBSON K-S TELEGAGE MADE BY H.{Arthur M. Hanbury - Head Complaints} M.{Mr Moon / Mr Moore} HOBSON LIMITED 47/55, THE VALE, ACTON, LONDON, W. 3. Telegrams: "ASSEMBLAGE, LONDON." Telephone: CHISWICK 4231 (4 lines.) The Hobson K-S Telegage consists of four units—the Head, Tank Unit, Triple Air Line Assembly and Hand Pump. 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 Pressure Balance Chamber and Air Line are merely a safety device, which protect the gauge against high pressure. 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 the petrol when the car is in motion. When the Air Cup is above the level of the petrol it is constantly being filled by the surge and splash. The 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 connected at the top to Pressure Balance Air Line and the back half is a Brass Tube. A U-tube containing liquid is the most accurate instrument known for measuring pressure. THE HAND AIR PUMP, is of the spring loaded type and to operate it the knob should be withdrawn when the plunger will return automatically pumping air to the Air Chamber. By means of this pump any air lost by absorption or contraction on cooling down may be at once replaced. THE TRIPLE AIR LINE ASSEMBLY, leads from the Tank Unit to Instrument Board. Three different sizes of Union nuts are fitted on the lines and each is screwed on its appropriate union on Tank Unit and Instrument Board. The Air Line is connected to Air Line connection on Tank Unit and Brass Tube on Dash Head. The Pressure Balance Air Line is connected to Pressure Balance connection on Tank Unit and Pressure Balance connection on Dash Head. The Pump Line is connected to Pump connection on Tank Unit and to the Air Pump on 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, or the Hand Pump operated. 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, or the Hand Pump operated, and will continue to rise until it records the true contents of the tank. 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.) | ||