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 analysis of vehicle oscillation, focusing on improving riding quality by addressing bouncing and pitching.
Identifier | ExFiles\Box 43\2\ Scan219 | |
Date | 23th August 1927 | |
Oy9-E-S2327 -2- August 23, 1927. Meanwhile, on the 40/50 K² is equal to about .45 a b to .55 a b, depending on the body and the loading, and being lower (and therefore worse) for the longer wheelbase. (This is obvious since a b is larger for the longer wheelbase.) Hence our efforts to improve riding quality concentrate on:- (a) Shifting mass towards the ends (to increase K²). (b) Using softer springs, particularly in front. ( Because these have most effect in slowing down the oscillation period.) (c) Developing more effective shock absorbers, particularly in front. Types of Oscillation. Sketch IV show the two types of oscillation which we are considering. In "Bouncing" the rear springs deflect more than the front. The centre of oscillation is probably only 12" or so in front of the front bumper. We fit soft rear springs to make this movement slow and "easy". We fit as soft rear shock absorbers as possible so as not to interfere too much with this movement, which is considered desirable. Frequency is 65 to 90 oscillations per minute. In "Pitching" the centre of oscillation is under the driver's seat, i.e. about 1/3 of the wheelbase from the rear axle. Therefore the front springs deflect more than the rear. Hence the front springs and front shock absorbers are the chief factors in controlling the speed and amplitude of pitching. Pitching is disagreeable - because it is fast (120 oscillations per minute) and because it throws the passengers off the seat-backs. American macadam roads are particularly inclined to promote pitching because of the spacing of the "frost waves" in the road. The above notes (a), (b) and (c), on improvements of riding quality, obviously apply more to pitching than bouncing. With very soft front springs, it appears that the front shock absorbers can be made very effective without jerking the car over pot-holes. | ||