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).
Extract from a letter detailing a fault with a petrol gauge and an investigation into its cause.
| Identifier | ExFiles\Box 44\4\ Scan032 | |
| Date | 6th April 1929 | |
| +9038 Extract from letter ref. GWH{George W. Hancock - Head Chateauroux}6.4.29. We reduced the pressure to 30 lbs. per sq.in. running at 60 m.p.h., so far we do not appear to have gained very much, the weather has turned cold, which gives us a better oil consumption in any case, therefore results may be misleading. The petrol gauge has not functioned correctly since we landed in France. Its action has been confusing, but we give what is our opinion after careful examination of the cause of the failure. If we take the position as thus - the rear tank full of petrol, the liquid in the gauge tube shewing full amount of petrol, we get the following results - there is a definite pressure in the pressure pipe holding the liquid up. In the balance line there is next to nothing. We take the car on the road and very quickly obtain a high speed before much petrol is used. A slight surging of the petrol in the tank is caused which causes momentarily a higher pressure in the balance line (which is important for it is still sealed with petrol in the tank) - the result being that a certain amount of air in the balance pipe is forced out, there being very little weight of petrol to keep it back. The next moment a certain amount of vacuum is produced in the balance line and petrol enters, afterwards it is drawn up the tube by the dropping of the liquid in the gauge, due to petrol being used until as we have found out it mixes with the liquid in the tube. We have found definite proof of this, each time it has been examined. The pressure line has always been dry, coloured petrol has always run out of the balance line immediately it was disconnected from the gauge. Our liquid is now useless as it is 50% petrol. We hope this is clear to you and should be much obliged if you will send along some more liquid as we intend to carry a junction from the balance line to the top of the filler cap to verify our investigations. A rough sketch is attached to shew our meaning. -------------- | ||