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).
Petrol pump failures caused by vapour lock, detailing diagnostic tests conducted on a run from Boulogne to Chateauroux.
| Identifier | ExFiles\Box 82\1\ scan0156 | |
| Date | 29th July 1933 | |
| X4513a. hotel de France. Chateauroux. Indre. 29.7.33. To Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} From G.W.H. B E N S P O R T We have received your memo Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}6/KT 27/7/33. PETROL PUMP We have allready sent you reports of failures experienced during our run from Boulogne to Chateauroux. These failures were definately due to vapour lock. The difference between our failure and the failure you experienced is, we have not had any signs of petrol shortage during the sustained high speeds. Our failure is after stopping a few minutes, when a complete failure occurs. We have proved that this failure is due to vapour. The pipe lines, petrol filter, are the cause. We have informed you that by short circuiting the mass of pipes etc. on the dash we overcome 90% of the trouble. We had whilst Hs{Lord Ernest Hives - Chair} was with the car a failure of the pump itself. This has not re-occured. We are trying out piece meal to get at the trouble, unfortunately the air temp. is much cooler. The following tests have however been carried out. (1) Filter suspended as near the bonnet as possible. Water temperature 100°C. Oil temp. 100°C Air temp. under the bonnet 65°C. (2) Result after engine had been stopped 2 minutes. Engine petered out after restarting and would not start again for some time. (3) No1 test repeated with the exception that as soon as engine was stopped a seperate petrol tank was connected direct to pump. (4) Result. Engine started and continued to run without any sign of fluttering. (5) Pump connected up to own tank, a glass tube replacing the feed from the tap on dash to filter. (6) Result. A rather surprising result is that the pipe line or glass tube was not kept full of petrol, but a small supply runs down as the pump functions. If the mixture is put over to strong the pipe line is immediately filled. There is a constant stream of vapour bubbles been drawn down the supply pipe indicating that the petrol in the pipe lines from the tank is evaporating With the temperatures as first stated the engine is continually luffing through this vapour coming through. | ||