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).
Optimal cylinder compression capacity for the 40/50 engine, comparing Derby and Springfield practices.
| Identifier | ExFiles\Box 19\7\ Scan079 | |
| Date | 5th May 1924 | |
| RECEIVED AH EM c. Hs.{Lord Ernest Hives - Chair} GMBY C.SPT. x790 EP{G. Eric Platford - Chief Quality Engineer}13/Hl.5.24. re. 40/50 Cylinder Compression Capacity. The compression capacity of the engines now being received on test appears to be slightly less than it used to be, and we are under the impression that this is due to the change of the valve from the tulip to the flat type. According to the drawing the old standard should be 25.75 to 26.25 cubic inches and according to the latest drawing should be 25.25 to 25.75 cubic inches, i.e. .5 cubic inches less. We believe the engines are now suffering from certain roughness, whereas we seem to be well in hand for power and general performance. We suggest, therefore, that we should keep our compression capacity to the maximum rather than to the minimum. Oy. reports that on Springfield chassis they specify this capacity to be 27 cubic inches, and they have realised this should be fairly exact and have specified limits of .25 cubic inches either way. In making comparisons we do not feel that they are lacking in performance as compared with our Derby chassis. It may be they claim an advantage in this respect due to their vaporiser scheme. We do not therefore wish the compressions to go up at this stage. In accordance with the experience we are now having and also in accordance with the experience Springfield are having it would appear that if anything we should go less, and instructions should therefore be given for the compressions to be as before, i.e. the mean compression 26 cubic inches with a .25 cubic inch limit either way, and even this is 1 cubic inch below Springfield practice. EP.{G. Eric Platford - Chief Quality Engineer} | ||