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).
Carburation issues, comparing the Doris and Derby schemes, and recommending the adoption of a proven American pilot jet system.
| Identifier | ExFiles\Box 50\3\ Scan231 | |
| Date | 8th August 1922 | |
| - 2 - EP {G. Eric Platford - Chief Quality Engineer} 5/H18.8.22. car as soon as ever possible and will give the comparative results as obtained on the dynamometer and on the road, particulars of which they have promised to supply to us as soon as they are taken. The chief difference in this scheme and the ordinary Doris scheme is that the petrol is drained to the bottom of the boiler on the exhaust pipe, and a pipe from the top of the boiler is again returned to the induction pipe. As we are experiencing carburation trouble with our own cars at Derby, and as this trouble will be worse during the coming winter, I strongly recommend that, failing the fixing of the hot throttle scheme and present design of pilot jet, which is not yet applied, we should immediately apply this scheme which has been a proved and tested scheme and has been used on American cars for over 10,000 miles. I also recommend that we should be in a position to apply this scheme to any cars on which the carburation is not satisfactory. As regards the Pilot jet used by America, there is no external adjustment for this jet, but the supply is pre-determined fixed and checked on test and it is surprising how this predetermined amount which is 40-50 Pts. per hour (see drawing) is consistently satisfactory for the successful running of the car. This pilot jet carburetter is rather larger than the Derby scheme, and although in making tests they appreciated that the Derby scheme seemed somewhat more efficient as regards the use of petrol, they rather feared that it would not be large enough to run the engine in the worst of their cold weather. They are quite anxious, however, to make comparative tests with the Derby Pilot jet over their existing type and will report to us as soon as these have been taken. The control for the pilor jet is fixed to the dash and the handle is rather large and heavy, so that it can be actuated by the foot. It must be realised that this pilot jet has been in service on their cars in America during the past winter and has given entire satisfaction. The one alteration they have made from the drawing is that the air inlet holes on the Barrel of the carburetter have been fixed at the bottom and not at the top, as they found that dust and foreign matter accumulated on the inside. EP. {G. Eric Platford - Chief Quality Engineer} | ||