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).
Investigating and solving petrol spray from the Phantom III carburettor breather pipe during braking.
| Identifier | ExFiles\Box 91\1\ scan0322 | |
| Date | 14th June 1936 | |
| C to E X300 a SEEN BY ALL TESTERS. HOTEL DE FRANCE. CHATEAUROUX. Indre. France. 67 To. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} 32. EX. - PHANTOM III Float Chamber Stand Pipe. We have been investigating with a view to overcoming the trouble of petrol spray issuing from the carburetter breather pipe when braking, as reported in our Daily Report of the 27/5/36. In comparing the two carburetters 25/30 HP. and Phantom III, it was observed that the design of the float chambers were entirely different. A test with the 25/30 showed that no trouble was experienced when braking as was the case on the Phantom. The Phantom carburetter has the vent pipe placed just above the chamber where the feed needle valve is located. This chamber is completely isolated by an aluminium partition from the rest of the float chamber, and is at the forward end of the carburetter. The petrol on braking, surges to the forward side and runs up the vent pipe situated immediately above it. This action is assisted by the extra flow of petrol from the pumps when THE FLOAT goes down, due to the petrol having surged to the forward end. To prevent this happening, we have put the vent pipe in the centre of the lid{A. J. Lidsey} where the petrol cannot reach, either accelerating or braking. We find this arrangement absolutely satisfactory under all conditions; we enclose two rough sketches, one illustrating the Phantom III float chamber, showing the isolated chamber and the new position of the vent pipe, and the other shows how the different design of the 25/30 HP. float chamber cannot produce this trouble. The isolated chamber referred to, becomes very hot with a high under bonnet temperature; when the engine is stopped, the petrol in this compartment evaporates, consequently, after a short time when petrol is again pumped through, it immediately vaporised and came out in the form of fine spray from the vent pipe. We have drilled holes at the bottom of the partition so as to give it some communication with the fuel in the main chamber, and we hope that this will prevent the rapid evaporation that occurs. The new position of the vent pipe eliminates the possibility of the spray of petrol being forced up and out as we have reported on previous tests at Mount Ventoux. [Signature] T.H. Hamilton. GWH{George W. Hancock - Head Chateauroux}/HFH.{Hoppy F. Hamilton} | ||