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).
Technical memorandum discussing different petrol tank and gas gauge designs, focusing on venting issues.
| Identifier | ExFiles\Box 19\3\ Scan379 | |
| Date | 19th May 1930 | |
| X7772 To: Ebn. from Oy. C. SETT. C. WHR.{Mr Wheeler} C. Mr. Soutter. C. Hyr. C. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} C. FS{F. Steele}/ST.{Capt. P. R. Strong} OYS/DW.19.5.30. Petrol Tank. Sec.7080. ------------------------ You recall the talk to Bandemor or King Seeley last winter on gas-gauges. Have now had a talk to Searight of H.M. Hobson on the same subject. Since I think a clear understanding will help us in handling both P.I and P.II I am retailing what I have learnt from Searight and others. (1) It is usual here to use a "muff" around the end of gas-pump filling hose, to check the back-flow of vapor. If these are tight to the filler spout it is possible to produce excess pressures of 6 lbs. in the tank. (2) In the Am. K.S. tank fitting the vent pipe is provided to prevent this pressure squirting all the liquid out of the gauge. The fuel can only enter the bell through the .040 hole at the bottom, and leaves the bell through a 5/16 pipe. So the pressure in the bell can never be excessive. This vent pipe discharges freely to atmosphere on the Am. P.I tank through the main tank vent. (3) A small air hole used to be provided in this vent pipe at top of tank. This was recently omitted by King Seeley. This was used because under conditions causing rapid discharge from vent pipe, if the filling hose is suddenly removed, the moving column of liquid in the vent pipe produces enough suction in the bell to suck the liquid back out of the U-tube. This would only occur with tank partly filled and gauge reading low. The small hole to air in tank "broke" this suction. With our large back-leg on the U-tube this hole was found unnecessary. (4) The English instrument has no vent pipe. England uses a high filler. If there were a vent from the tank unit, excess fuel in the filler spout above full tank level would be bound to discharge through the vent pipe to the floor every time the tank was filled. You remember we found this on earlier cars and changed to low filler and central vent for this reason, and also because of spilling of the fuel on left-hand turns. cont'd.{John DeLooze - Company Secretary} | ||