Letter to C.W. Hancock discussing carburetter acceleration lag and crankshaft torsional period test results.
| Identifier | ExFiles\Box 11\4\ 04-page023 | |
| Date | 3rd May 1932 | |
| C.W.Hancock from Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} Hotel de France, Chateauroux(French test region), Indre, France. We thank you for your report of May 1st. Grylls has written to you on the gear box troubles. CARBURETTER. We are following on with the carburetter tests here and as soon as we get any results worth having we shall send the parts out to you for confirmation. We have an impression that the lag in acceleration may be due to the large capacity between the jet and the diffuser. We are trying various accelerating wells which will carry a quantity of petrol near the diffuser and which will come into operation upon suddenly opening the throttle. We find on the two little 25 HP. carburetters that we lack snap acceleration which we put down to having a low fuel level in the diffuser because we have not got diabolo floats as on the twin choke carburetter. The accelerator pumps on these little carburetters are not powerful enough to raise the level in the diffusers sufficiently for snap opening up. This is interesting as it is more or less the same condition as we have on the expanding carburetter. CRANKSHAFT TORSIONAL PERIOD. Naturally, when thinking of the slipper wheel you will be suspicious of timing gear rattles. We are rather concerned to find that the Test Dept. are running all their P.II slipper wheels at 14 lbs. load. Apparently this was fixed up between yourself and Mx. {John H Maddocks - Chief Proving Officer} to eliminate bus knocks. All our records show that we have never run a car in France with less than 18 lbs. load and even with this load you are now reporting crankshaft half speed periods. Fairey's car we tried the other day had a very marked high speed period but at the time we did not appreciate that the damper was only set at 13 to 14 lbs. load. We should like to know exactly what you have fixed up with Mx. {John H Maddocks - Chief Proving Officer} because unless there was a very good reason for going to 14 lbs., we think we should revert to the load at which we ran our 10,000 mile tests. We know that the Test Dept. can always get away with a lighter damping load than we can on their new cars and for that reason we want to stick very closely to the loads we find satisfactory on the completion of the 10,000 mile test. | ||
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).