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).
Fuel supply issues related to vacuum pump efficiency at high temperatures and cooling system fan belt tests.
| Identifier | WestWitteringFiles\U\May1930-July1930\ Scan126 | |
| Date | 28th July 1931 | |
| -2- H.S./28.1/E.L./28.7.31. Contd. As soon as the car was stopped this temperature exceeded 80°C. with unventilated bonnet. It seems feasible that the vacuum pump would fall off in volumetric efficiency at these temperatures due to the low boiling point of petrol giving us a worse result than can be obtained on the road wheel dynamometer, where everything is shielded from the exhaust and kept as cool as possible with the bonnet off etc. We are continuing tests to see exactly what does happen. We have given prominence to this question of fuel supply because we think it is likely to cause weak mixtures at high speeds which, we shall show later, have a bearing on overheating. Actually, we have not recently had any reports of fuel shortage on our 10,000 miles tests, and have only a few isolated complaints from customers of the trouble; which shows that full throttle can seldom be held for three minutes on the road. It is, however, clear that as we are so much on the border line, any variation in the vacuum pump or autovac efficiency will cause trouble as will any slight air leaks on the suction side of the pump such as in the two-way tap or in the soldering of the tank filter tubes. Trouble caused by such leaks in service has been brought to our notice. COOLING SYSTEM. - FAN. - We confirmed our previous result that the standard spring loaded Whittle belt is incapable of driving the fan satisfactorily at high speeds. We have an alternative endless canvas rubber belt which has a much better life and will drive the fan when spring loaded but causes it to dance about rather too much. We think that this might be used with the tensioning | ||