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).
Vehicle suspension dynamics, pitching, and ride comfort, using analogies of a ship and a see-saw.
| Identifier | ExFiles\Box 67a\2\ scan0020 | |
| Date | 4th September 1927 guessed | |
| - 2 - I think you will agree that a ship which is trimmed by the head is more uncomfortable than one which is trimmed by the stern in a sea way, that is to say, trimming by the stern is the lesser of the two evils except with a fast following sea. You will also agree, I think, that the "tipping centre" of the unsprung weight will be further forward than "tipping centre" of the whole car weight, and I believe that the former point is much too far forward for comfort in our present cars with usual weight distribution. Another point I would like to raise for your consideration is the usefulness, or otherwise, of springs in the squabs, which springs must have a period and tendency to throw passengers forward on rebound. I think that the removal of springs from squabs and replacement by air cushions would ameliorate this trouble without creating any discomfort. After all in pitching the car may be likened to a plank of see-saw having the fulcrum at its "tipping centre", and if this "tipping centre" does not approximate to the longitudinal centre of the car then there must be a considerable difference between the amplitude and speed of motion of one end and the other; the end nearer to the fulcrum having the lesser velocity and lesser amplitude. Also, the more the total weight is forced forward or aft over the axles the slower will be the natural pitching period. If the weight were concentrated in the centre immediately over the fulcrum the extreme ends of the see-saw would be capable of being oscillated in a vertical direction at very high speeds indeed, thus causing discomfort. The matter is further complicated by the fact that the period of the rear springs of a car is affected by suspension at the front end of the car and vice versa, that is to say, if the period at the rear is taken with the front of car carried upon its ordinary springs it will not coincide with the period if the front end of the car be supported on a trestle or other solid foundation, so that there appears to be a mutual reaction of the front upon the rear and rear upon the front springing period. This question of being impelled forward reminds me of a grain conveyor which I once saw working in England. This conveyor was practically a long shallow trough carried upon supporting girders and attached thereto by numerous legs of flexible flat laminated timber at an angle on either side of the conveyor, that is to say, these supporting | ||