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 from the American office to Derby, England, offering comments on spring suspension, specifically regarding bouncing frequency.
| Identifier | ExFiles\Box 43\2\ Scan192 | |
| Date | 26th January 1927 | |
| 43900 ROLLS-ROYCE OF AMERICA, INC. SPRINGFIELD, MASS. Oy1-E-12627 January 26th, 1927 Mr. E.{Mr Elliott - Chief Engineer} W. Hives, Rolls-Royce, Ltd., Derby, England. (Copy for the attention of Mr. Haldenby.) Dear Mr. Hives: Re Spring Suspension We have your exceedingly interesting notes on "Suspension" (Fundamentals of Car Performance). I would like to offer the following comments. (1) Bouncing Frequency (p.6). I believe I sent you a copy of my report of Nov.10/26 to R.{Sir Henry Royce} on our tests of moment of inertia of complete cars. But in any case am enclosing a copy. These results showed clearly that the frequency in "pitching" or "bouncing" does not necessarily have any direct relation to the spring deflection under normal load. That is the time period equal to 2π√(e/g) is not true. It is in fact only true for the suspension of a single mass on a single spring, or the suspension of a car in which K² is equal to a x b (i.e. the masses are so distributed that they may be taken as concentrated above the axles). We think this never occurs in practice but is more nearly approached on the shorter cars. (We should like you to swing a 20 hp.) To illustrate this I enclose a sketch showing the case of a mass midway between a pivot and a spring. The masses are the same, the deflection of the spring under load is the same in each case. Yet the frequency in the second case is 1.41 of the first case. We believe the second case represents the typical condition of a long wheelbase car. | ||