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).
Spring oscillation, natural frequency, and its effect on passenger comfort, including the formula for the period of a spring.
| Identifier | ExFiles\Box 178\1\ img178 | |
| Date | 28th August 1926 | |
| - 6 - Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}1/LG28.8.26. oscillation can be built up at a certain rate - say 80 impulses per minute. This rate of oscillation is known as the frequency of the rear springs, or the number of complete periodic movements which the rear springs naturally wish to make in one minute. The periodicity of the rear springs is the time (usually measured in seconds) that they take to make one complete oscillation. Now the reason the natural frequency of the suspension is important is because it is this which dictates whether a passenger will be sea-sick or not. When the car goes over a bump, if no shock absorbers are fitted, the body will continue to be moved up and down by the free oscillation of the springs. If these occur at a frequency below about 70/min. there is a danger of the passen- gers suffering from sickness. Now, given the deflection of a spring in its loaded position, it is quite easy to calculate its natural period. Every spring having the same loaded deflection should have about the same natural frequency of vibration. Actually the internal friction of the spring, or damping factor, has a certain amount of influence on the result. The formula for the period of a spring is:- Period = 2 π √m/k = 2 π √g Where m.{Mr Moon / Mr Moore} is the sprung weight, k.{Mr Kilner} is the spring stiffness and √ the static deflection. In other words the period is directly proportional to the √ deflection on any spring, to the √ load on any spring of given rating, or inversely proportional to the √ spring rating with any fixed load. contd. | ||