Optimum Damping in a Randomly Excited Non-Linear Suspension

Analogue computer studies of an automobile suspension on a simulated random road show that optimum ride and road holding can be achieved with linear damping for all magnitudes of road roughness. Unsymmetrical damping, however, provides better isolation from large bumps and obstacles at the expense of only very moderate increases in the mean-squared values for random inputs. Optimum values for the ratio of bump to rebound damping rates are obtained by use of an integral-square criterion. For a linear system the effects of the seat dynamics and road power spectrum characteristics are illustrated using the results of a digital computer program. The influence of the non-linearities on mean-square values is analysed theoretically and the statistical describing function method applied.

Second Paper: Recent Developments in Exhaust Manifold Reactor Systems

Exhaust emission control systems employing air injection and exhaust manifold reactors in place of conventional exhaust manifolds have been developed to control vehicle emissions to 0·25 gram (20 p.p.m.) of hydrocarbons and 5·0 grams (0·22 per cent) of carbon monoxide per mile. These low emission levels have been achieved with good driveability, good vehicle performance and very little loss in fuel economy. Durability tests of a number of exhaust manifold reactor systems indicate that acceptable life in consumer service can be attained. Non-nickel alloy steels developed by specialty steel manufacturers, and based on the iron-chromium- aluminium system, appear to be useful materials of construction for reactors. These alloys coupled with the now demonstrated simplifications in reactor design offer one route to lower ultimate costs of these units. The commercial development and application of exhaust manifold reactor systems seems entirely feasible.