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).
Data summary from test bed runs of a Graham Supercharger fitted to a Bentley.
| Identifier | ExFiles\Box 140\1\ scan0095 | |
| Date | 19th December 1934 | |
| To E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to By: x209 Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}6/KW.19.12.34. Graham Supercharger on the Bentley. We have obtained a certain amount of data on the Graham Supercharger on the Bentley which we have been running on the test bed. A summary of the results so far obtained is as follows :- (1) When run with cold water instead of hot water in the supercharger casing the Graham blower picks up 6 H.P. (2) When run with an expanding carburetter instead of the fixed choke carburetter used on the Graham, a further 7 H.P. is gained. (3) In order to obtain the maximum performance at low and high speeds a semi-expanding type of carburetter is required. Comparing curves 2 and 4 it will be seen that the fixed choke carburetter enables a better power output to be obtained with the blower at speeds below 3,000 r.p.m. than can be obtained with the S.U. This confirms the Graham people's assertion that the blower is very sensitive to any depression at its suction side. (4) We have obtained better slow running results putting exhaust gas through the blower casing than using water. This means that if we can evolve a satisfactory thermostat control for the exhaust heat to the supercharger, we can have the required amount of heat for slow running at low speeds and cut the heat off completely at high speeds, so improving the power output. The position of the blower is as shown on the attached sketch. We have so far tried two pipes only: of these the short one with the wingle bend was much better than the long one with a double bend. Nothing we could do to the long pipe, not excluding heating it the whole of its length, would produce good slow running. The short pipe gave good slow running with exhaust heat only passed through the blower casing. | ||