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).
Summary of suggestions and criticisms regarding the Hobson gauge system.
| Identifier | ExFiles\Box 44\4\ Scan159 | |
| Date | 16th January 1930 guessed | |
| - 4 - 6. When the liquid in the U tube is at the top they find as a matter of precaution that there should be not less than 1/4" of liquid above the outlet of the capillary tube in the rear leg. Otherwise air is liable to pass over into the gauge tube and drive the liquid into the pressure balance line. 7. Summarizing. Their suggestions on the present Hobson gauge, which scarcely amount to criticism as they do not know enough about it, are as follows: - 1. They think the 3 pipe system with pump is unnecessarily expensive for car use, but agree that the pump permits rectification after standing. 2. The pressure balance line introduces possibilities of error due to entry of gauge-liquid at the front end or fuel slugs at the rear. (Improved baffling at rear and removable joint at top of glass tube in front). 3. Doubt as to height of liquid in rear leg when gauge-glass reads full. 4. Connection of hand pump, with screw down needle and tire valve to top of stand pipe in tank, to introduce pure air to the standpipe and keep vapor down. With this system use larger hole (.100 to .125 in bottom of bell. 5. With a hand pump believe the "house" or "aeroplane" type of gauge without Sprengel pumps is most satisfactory. 6. If Sprengel pump is used it should be of new type giving 100% delivery of pure air. 7. Better joint on bottom of gauge glass. Note: The removable joint at the top of the gauge-glass permits easy adjustment of the correct liquid-level in the gauge glass by means of drops of guage-liquid introduced into the top of the glass tube by a match-stick. This is the method of setting the gauge which we, and everyone else, use. Yours very truly, Maurice Olley Maurice Olley M Encl: SK-378 A-14132 | ||