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).
Design of a centrally vented petrol tank versus a balanced line gauge.
| Identifier | WestWitteringFiles\V\March1931-September1931\ Scan047 | |
| Date | 13th March 1931 | |
| HS{Lord Ernest Hives - Chair}/RM.{William Robotham - Chief Engineer} FROM DA{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork} DA{Bernard Day - Chassis Design}/EV{Ivan Evernden - coachwork}3/M13.3.31. Copy to SG.{Arthur F. Sidgreaves - MD} x4038 REAR END OF P. 2. x7460. HS{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer}3/MJ9331. x4531. We thank you for your letter and regret to say that we fear you have forgotten that you were the co-disciple of OY. in advocating the centrally vented petrol tank with single line gauge. At your request we persuaded R.{Sir Henry Royce} to allow us to make a design based on the model K.{Mr Kilner} S. fitting you left with us. The single line gauge was then your only hope of curing the troubles. A central vent must of necessity be high above the tank top compared with our present gauge fitting or it will spill on accelerating or hill climbing. We believe you will find the present design too low. (It is lower than that used by RRAI.) Also the dia. of the vent must be large (OY. asked for 2") or else pressure will bebuilt up in the tank during filling which will expel all the liquid in the gauge tube. Our vent as drawn is that of the model you gave us. It is recognised by RRAI. that the vent will spill when the tank is full (our side filler vent does now) and if it spills over the rear apron it destroys the paintwork, especially on light coloured cars. It must therefore spill beneath the apron. Our central vent is cleaner, smaller, and lower than that of RRAI. for P. 1., so we do not see why they should object to it as you say. The advantages of the central vent are: (1) Rapid filling. (2) Sprengle pump, using fresh air and one line, with no hand pump. (3) Cheapness of the gauge. The disadvantages are: (a) The central vent is high and will interfere with bodies having a rear trunk or boot. (b) On such bodies with trunk or boot petrol vapour will be trapped under the body. (c) Petrol spills either under or above the apron - either is bad Since you have now perfected the present balanced line gauge we would prefer to adhere to the vent in the filler, and if possible we would like to redesign the present tank fitting to improve its rather large and ugly appearance. One suggestion is that the aluminium cover could be removed when an apron is fitted. This would reduce the height of the bulge. DA{Bernard Day - Chassis Design}/EV{Ivan Evernden - coachwork} | ||