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).
Letter providing feedback on carburation, synchro-mesh gearing, and control placement on a Bentley.
| Identifier | ExFiles\Box 89\4\ scan0092 | |
| Date | 11th May 1934 | |
| - 2 - COPY. and in particular to my letter to you of the 26th May.) Carburation. Owing to the design of the S.U.Carburettor at present employed, an appreciable delay occurs after depressing the throttle pedal before the full increase of power is developed. To any one accustomed to the instantaneous acceleration provided by the modern down-draft pump type carburettor, this delay is very noticeable - not only in the actual loss of useful acceleration in traffic but in the 'feel' of the car which by comparison is sluggish. Admittedly, the acceleration which follows the hesitation is excellent, but often the available split-second and always the whole of the impression of livliness and speed is meanwhile lost, and this latter impression is surely more important to you, as manufacturers, than the ultimate performance. As evidence of how subtly the action of these carburettors ruins the impression of livliness of the car, my case may be of interest. I recently carried out on my Bentley the acceleration tests to which I submit all my cars, and although I had been driving the car for a year, constantly studying its performance with great interest, I was amazed by the results which were far better than I would have thought possible from a car with so mild a response to the throttle pedal. Acceleration from one constant speed to another is fair, but if the throttle is opened in advance at a lower speed and the same test repeated acceleration is phenomenal for an unsupercharged car of this type. It seems a great pity that the tremendous impression of liveli-ness which this car should give should be lost through not fitting a different type of carburettor. Synchro-mesh on second speed. As I wrote to Major Cox on the 11th May 1934: 'To my mind, the chief charm of synchro-mesh is the ability to engage the desired lower gear whilst braking up to a street corner or obstruction without having to remove the right foot from the brake pedal - and this gear, in the case of the Bentley, is or should be, nine times out of ten, second gear.' For this reason I feel that the addition of this refinement to second speed, especially to a higher geared sports car like the Bentley, would be of the greatest value. Moreover, I think you will agree that one is entitled to expect on such an expensive car a refinement which is available on many small and cheap XXXXX ones. In view of the recent adoption of this feature on the Phantom III Rolls-Royce I feel that to stress its merits would be XXXX merely 'speaking to the convinced'. Controls. Lastly I would like to see the steering wheel cleaned up the removal of the throttle and spark controls to the dash. Thanks to the admirable working of your automatic spark control the over-riding hand control is only needed in case of failure of the start | ||