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).
Test bed results and manufacturing inaccuracies of a Spectre Camshaft.
| Identifier | ExFiles\Box 93\5\ scan0005 | |
| Date | 9th July 1934 | |
| To REC. X4644 307 Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}6/KW. 9.7.34. SpectreCodename for Phantom III Camshaft. Further to our conversation about the balanced camshaft, here are test bed figures which have so far been obtained. Naturally it is difficult to measure anything very accurately under test bed conditions, but we think the results obtained are quite sufficient to indicate large inaccuracies in either the cam form or in grinding. In the first place, the angle between the cams is incorrect. The cams should have 4° of overlap; in actuality they have about minus 4° of overlap or an error of 8° on the crankshaft which means 4° on the camshaft. Secondly, the duration seems to be wrong on some of the forms. The correct duration for the inlet valve and .020 tap clearance is 230°. As you will see, three cams come out at about 220°. Similarly, the exhaust valve duration should be 234° and one cam actually measured is only 222°. Finally, the toe of the camshaft which is responsible for the silence or otherwise of the mechanism does not remotely resemble the drawing of B-6 cam and from the sound is equally bad on a number of others. As this really is entirely a manufacturing question we would rather you dealt with it than we did. We should be glad to know whether your own measurements confirm our results. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||