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 report on improving gear rattles in the Phantom II Spring Drive through adjustments to ignition, compression, and spring loading.
| Identifier | ExFiles\Box 179\2\ img112 | |
| Date | 2nd January 1932 | |
| To R.{Sir Henry Royce} from Ha/LHS.{Lord Herbert Scott} c. Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. Dm.{D. Munro} E.{Mr Elliott - Chief Engineer} c. Ry. PHANTOM II SPRING DRIVE (S.79915) Tests have been carried out on the Test Bed Unit in order to improve gear rattles at 550 to 650 R.P.M. full load. These rattles are only slight on the majority of Phantom units, but it was very noticeable on 27-SK chassis, the unit in this chassis having a compression ratio of 5.22 : 1. We find that by retarding the ignition until detonations cease, the rattles are considerably improved, this being done on the bed unit which has a compression ratio of 4.9 : 1. This means that on a high compression unit as in 27-SK running with standard ignition settings, detonations and subsequent gear rattles are more pronounced. When we obtain the next 5.22 : 1 compression ratio cylinder head we will give definite ignition setting figures which cure detonations and improve gear rattles. The speeds of the rattle periods are unaffected by alteration to the spring driving load or the frictional loading. There is a slight improvement to the intensity of the rattles by increasing the spring driving load from standard which is 19 lbs. at 17.5" radius to 24 lbs. at 17.5". If the loading is further increased to 30 lbs. at 17.5", the improvement is considerable, the rattles being only slight. To obtain this loading it is necessary to fit double driving springs, the particulars of which are as follows :- Outer Spring to Hs.{Lord Ernest Hives - Chair}481. .750" free length; requires a load of 70 lbs to compress to .500" ; mean diameter of coils .625" ; diameter of wire .110" & 3 1/2 working coils, 4 1/2 coils in all. Inner Springs. .750" free length; requires a load of 27 lbs to compress to .500", mean diameter of coils .425" ; diameter of wire .072" (15 S.W.G.) & 5 working coils, 6 in all. We find that as the frictional loading is increased the rattles become more intense, and that if a light frictional loading of 8 lbs. at 17.5" radius, in conjunction with a heavy spring driving load of 30 lbs at 17.5" radius be used, the rattles are almost cured at 550 to 650 R.P.M. full load, this being the period complained of. By having the light frictional loading, however, the half torsional period becomes more obvious, and in order to avoid this, a compromise is effected by using frictional loading of 18 lbs. at 17.5" radius. | ||