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).
Engine valve springs, camshaft timing, and radiator design considerations.
| Identifier | ExFiles\Box 70\1\ scan0093 | |
| Date | 15th September 1927 guessed | |
| contd :- -4- It is probable that we shall have to make these springs from our usual wire by the usual process, but it is understood that a brand of Swedish tempered music wire is the best that can be obtained for these springs. The design which we have made gives a maximum pressure, valve open, of 95 lbs. We do not wish this pressure to be higher than is necessary to keep the valves from bouncing at 3000 r.p.m., the speed at which it is intended to run the engine, and which it must be tested for quite a long period, and very carefully analysed in respect of torsional and crankchamber vibrations, valve bouncing, push-rod reliability. It is understood that two of the present exhaust valve cams will be used if we use rollerless tappets, that the angle between the cams will be 111°, and that the timing will be as shewn in the accompanying sketch, which shews the way of checking the correctness of the cams. We believe this camshaft will be quite right, but would probably be better if the whole camshaft were say five crankshaft degrees later relative to the crankshaft. [Diagram Text] IN EX 43 IN 73 EX Timing shews heavy accelerations only. clearance = .012 It will be noticed that we wish the timing in the future to be always taken with a [illegible] sufficient cold clearance, to give the point of the commencing of the rapid acceleration, as at anything but the lowest speed we look upon the whole of the toe as a closed valve, though for running the clearance when hot must be such that we take up the whole of the slack during the slow lift portion of the cam, (i.e. for silent running.) (11) RADIATOR. Regarding the radiator, it would appear that this is quite satisfactory. It is necessary to fit the bonnet with louvres, and those recently designed appear quite satisfactory. In conjunction with the bonnet we have arranged that this will pass over the dash for simplicity and better appearance, as is adopted in the RR. American chassis, with the new form of bonnet clip and lock, as these make the bonnet easier to fit and handle. We have now made these bonnet clips simpler to construct, and as all the surfaces are machinable the finish should not be so costly as at present, considering that they save handles and much fitting. contd :- | ||