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).
Power output and performance of three different camshafts.
| Identifier | ExFiles\Box 13\2\ 02-page071 | |
| Date | 29th May 1931 | |
| To H.{Arthur M. Hanbury - Head Complaints} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to ES. Wor.{Arthur Wormald - General Works Manager} c. to H.{Arthur M. Hanbury - Head Complaints} Da.{Bernard Day - Chassis Design} c. to BY.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rh.{R. Hollingworth}8/KT.29.5.31. JAPAN I. POWER OUTPUT. With reference to R3/M2L.5.31. we have tested three camshafts to the forms you mention, i.e. Loc.1153 & 1158., and the two best i.e. 119º and 113º - were reported upon in Hs{Lord Ernest Hives - Chair}/ACL.1/U.23.5.30., 20.11.29., 9.11.29., and Hs{Lord Ernest Hives - Chair}/19.5.30. We give below the actual timing obtained at .013" tappet clearance, from which you will observe that they agreed very closely with two of the camshafts mentioned in your memo. We are really very pleased with the 112º camshaft results obtained in these tests for a normal as opposed to a sports type of motor car. We are afraid, however, that we have not made it quite clear why the 112º camshaft is not being used on the present production China cars. With the twin low depression carburetter and a free exhaust as shown in V.869 attached, the 112º camshaft gives excellent results. However, with the standard carburetter and standard exhaust system these results are rather negatived, in fact the 112º camshaft is actually inferior to the 110º camshaft below 2200 RPM. The desirability of a good MEP. at low speeds for R.R. cars was emphasized by a series of comparative road tests between the two camshafts on a standard China unit and it was decided that we could not afford to change on the standard car, as its performance getting away from traffic jams etc was impaired. The position is, therefore, that we can almost get the figures you suggest with the existing 112º camshaft if we have the twin or low depression carburetter and a free silencing system, but without these two features we can make little or no use of the much improved camshaft that you have already given us. With regard to the 3rd. camshaft which you suggest (No.2) you will note that on V.869 the effect of closing the inlet 5 or 6º later was to drop the power at low speeds from 2500 RPM. downwards to a very appreciable extent. The timing diagrams at .013" clearance which actually gave these two results are as follows - | ||