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).
Misleading oil relief valve pressures for the 40/50 chassis, suggesting revised figures for drawings.
| Identifier | ExFiles\Box 66a\4\ scan0001 | |
| Date | 12th June 1925 | |
| R.R. 493A (50 H) (D.D. 31. 12-6-25) J.H.D. EXPERIMENTAL REPORT. Expl. No. 48205 REF Hs{Lord Ernest Hives - Chair}/AJL1/LC41125 To BY/SS.{S. Smith} from Hs{Lord Ernest Hives - Chair}/AJL. Re. 40/50 Chassis - Oil Relief Valve. Sec.5205 With reference to your BY/SS{S. Smith}1/DB{Donald Bastow - Suspensions}24.9.25. It appears that the figures regarding oil pressures obtainable when using the spring E.72836, as given on the gen.arrgt. drawing E.72843 are somewhat misleading. On reading these figures the natural inference is that one will obtain the following oil pressures regardless of oil flow :- 25 lbs/sq.in. to the main bearings. 3½ " " " " rocker shaft. 1½ " " " " timing gears. The last two itemes are correct according to the wording, but the 25 lbs/sq in is the pressure at which the main valve starts to open; this of course, increases considerably as the flow of oil increases owing to the valve lifting against the spring. It would appear advisable to alter the drawing in order that no misunderstanding occurs in the works. We suggest that the wording be altered to indicate the pressures at which each valve commences to open - viz :- Main bearing 25 lbs/sq.in. Rocker shaft 1.25 lbs/sq.in. Timing gears 1 lb/sq.in. One can quite understand the failure of the works rig to produce the pressures as at present indicated on the drgs., owing to the limited available oil flow as compared with the condition when fitted to the engine. The rig as at present fitted up is perfectly capable of ensuring that the valves lift at the correct pressures, which we imagine is all that is required of it; the pressures at which the valves lift should therefore be stated on the drg. and not the pressures which are obtained under running conditions. These latter pressures are of no interest to the prope assembling and testing the valve unit. We know that we shall get the pressures we require to the various engine components if the valves commence to lift under the pressures stated above. These figures only therefore should be worked to. We are not at present in a position to fix limits to these figures - they should therefore be worked to as they stand for the present time. Hs{Lord Ernest Hives - Chair}/A.J.Lidsey | ||