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).
Results of engine knock tests and vehicle performance measurements.
| Identifier | ExFiles\Box 150\1\ scan0164 | |
| Date | 6th August 1936 guessed | |
| - 2 - RESULTS Knock Tests - These were made by C.F.R. Uniontown Method i.e. by driving the car at full throttle, with full spark advance, through the speed range at which knock commences and ends. A large number of observations were made on each fuel and with each set of plugs, and a graph is attached with conventional plotting. Commercial 67/68 O.N. Using original plugs gave light knock at 20 m.p.h. rising to medium between 25 and 30 m.p.h., falling to light at 40 m.p.h. with extinction at slightly over 50 m.p.h. Changing to new plugs knock intensity decreased slightly commencing later, at about 30 m.p.h., with extinction at 50 m.p.h., maximum intensity was never more than light minus and occurred about 40 m.p.h. Shell 70/71 O.N. Faint traces with original plugs between 30 and 40 m.p.h. With new plugs it was doubtful if any knock occurred at all, occasional very faint traces suspected at about 40 m.p.h. B.P. Ethyl (I.C.I. Type) 79/80 O.N. No knock observable with either original or new plugs. A final check was made on the Shell in the car's tank on both sets of plugs - no knock could be produced and from this it was inferred that plug deterioration was negligible and that the tendency for the engine to knock less as the tests progressed was probably due to the amount of full throttle running, which driving on the Track permitted, burning out small accumulations of carbon which produced the knocking observed previously. PERFORMANCE The Tapley Meter is a pendulum type accelerometer which records pull in pounds per ton. It is a delicate instrument and results from a short test, like this, with an unfamiliar car, must be regarded as approximate though comparative. The rolling resistance of the car, and this includes wind resistance, was first ascertained and determined as 50 lbs per ton at 30 m.p.h. and 100 lbs per ton at 60 m.p.h. - good figures showing the car to have reasonably low air resistance. Average pull was: 257 lbs. per ton at 30 m.p.h. 208 lbs. " " " 60 m.p.h. 154 lbs. " " " 80 m.p.h. which approximates a H.P. curve at the road wheels of 53 h.p. at 1500 r.p.m., 91 h.p. at 3200 r.p.m. and 118 h.p. at 4300 r.p.m; figures which must not be taken as exact but comparable with the power to be expected from the engine. The various fuels tested showed but little difference on the Performance Meter, all differences being within errors of observation, the fact that maximum speed over the half mile on all fuels only varied between 21.4 and 22 secs. confirms this observation. It should be noted though that Commercial tended to give lower performance figures and also the slowest readings over the half mile - speeds there varying from 81.81 m.p.h. to 84.11 m.p.h. - in all cases with slight adverse wind - readings being actual speeds taken with stop watch. Incidentally the actual maximum speed of the car under these conditions appears about 90 m.p.h., which is up to standard. | ||