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).
Technical discussion on suspension spring flexibility and ride comfort issues for the 20 HP and Phantom 40/50 HP models.
| Identifier | WestWitteringFiles\S\June1928-August1928\ Scan102 | |
| Date | 25th July 1928 guessed | |
| contd :- -2- The 20 HP. springing seems to satisfy customers. The Repair Dept, in conjunction with the Expl: Dept: go to the limit of flexibility in cases of complaint, but the increase in flexibility that can be utilised with the present spring design is not large if the principle of making a car always fit for Continental work is adhered to. PHANTOM & 40/50 HP. We are always in difficulty with these cars. Our problem is, flexibility V.{VIENNA} controlability. Whatever we do to the cars within practical working limits we are haunted by the 20/30 m.p.h. joggle on good roads which we can only eliminate by altering the weight distribution somewhat drastically. Some cars are much better than others, but if we go to the absolute limit of flexible springs, this trouble will still exist on the majority. Our experiences are :- FRONT SPRINGS. Standard, 3.1" initial deflection, 1.75" buffer clearance. Spring stiffness dictated by front wheel brakes. Immunity from hitting the buffers only just sufficient. With axle control we can use American type springs which have 3.6" initial deflection but we have tested them and so far feel that the improvement they give in the rear seat riding does not compensate for the lack of car control. REAR SPRINGS. When originally designed the 40/50 spring had 6" initial deflection and 6" buffer clearance (approx.) The std. now is 8" deflection and 4" buffer clearance which we have repeatedly proved is the limit for comfortable Continental work. The Repair Dept. using discretion, drop to 9" deflection and 3" buffer clearance in exceptional cases. If we drop all rear spring poundages 10% we shall probably be working at less than 3" buffer clearance whenever the car has a full complement of passengers and luggage. Even so we are sure we shall still have low speed riding complaints and shall probably encounter a crop of high speed troubles. We cannot help feeling that the scheme for carrying two spare wheels at the back which we have for India lll. will assist us in getting good riding on Coupes and light four-seater cars if we are able to utilise it. We think that the new type hydraulics and plated springs may help us further to improve matters. There is no doubt that we get many more criticisms of the Phantom suspension than any other feature on the cars, but we think that we have already reached the limit of flexible road springs. Weight distribution does seem to be a vital factor or we should not get so much better riding on the 20 HP. with 5" rear spring deflection than we do on the Phantom with a 9" spring deflection. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||