Proceedings of the Institution of Mechanical Engineers,Part D: Journal of Automobile Engineering

The quest to improve the fuel economy of General Motors passenger cars has led to the investigation of an engine-flywheel hybrid powertrain at the GM Research Laboratories (GMR). An engine-flywheel system was designed for a compact car and its performance was predicted analytically. The sytem was estimated to achieve an improvement in EPA composite fuel economy of 13 per cent ooer a 1984 production compact car. This margin of improvement was judged insuficient to justify the complex drivetrain, and, therefore, a prototype system was not built. However, the current potential of engine-flywheel hybrids for GM passenger car applications has been defined, and the technology areas requiring additional research attention have been identified.

The deterioration of the medical condition of stretchered patients during ambulance transport is discussed. The dominant vibration is generally low frequency (below 10 Hz) and in the vertical direction. Assessment of the sensitivity of supine patients to front-to-back vibration is referred to.

Methods of alleviating the vibration experienced by stretchered patients are discussed and particular types of stretcher suspension described.

This suspension has a constant natural frequency of vertical oscillations over a wide range of patient mass. A stretcher ride height (above the ambulance floor) independent of patient mass is achieved.

The stretcher suspension was tested over four types o surface (one ofl-highway), using a commercial vehicle having a chassis similar to that of a commonly used ambulance. Vibration of the vehicle floor and of the stretcher in both the vertical and the pitch senses was measured using accelerometers.

Transmissibility of the stretcher suspension, the stretcher frame and the stretcher mattress was obtained. The vertical vibration level (averaged over the four types of surface) experienced by the patient is compared with vibration tolerance levels for supine patients. Vibration inputs are closest in magnitude to the vibration exposure limit in the range 1.5–4 Hz. The transmissibility of the suspension in this range is between −7 and −9 dB.

Subjective evaluation of the suspension has been favourable.

Some modifications to the method of characteristics for the analysis of the gas exchange process in internal combustion engines are presented in this paper. The modifications are related to the calculation of the path lines and the Riemann characteristic lines at the grid points. Regarding the path lines, the algorithm for the generation and elimination of path lines has been improved, mainly for the cases in which the fluid motion passes from being null or going out of the pipe to going into the pipe. In those cases the algorithm proposed by Benson can cause some mistakes in the entropy level field of the duct. An alternative method is proposed: the duplication ofpath lines. The other modifcation proposed is related to assuming a linear interpolation for the pressure and the volume flowrate between the nearest grid points, rather than assuming a linear interpolation of the value of the Riemann characteristics. These modijcations substantially improve the results obtained in the calculation of the fluid flow in manifolds of reciprocating internal combustion engines.

The geared permanent magnet d.c. starter motor has several significant advantages over the wound-field starter, some of which are discussed. The acceleration performance and the cold cranking are shown to depend on both the battery internal resistance and the motor armature resistance. Typical motor characteristics and principles of design optimization are discussed, and it is shown that a motor of reduced weight and high efficiency is achieved compared with comparative conventional machines.

An overview is given on hydraulic anti-lock systems with direrent pedal characteristics, power supply concepts, and physical configurations suitable for ‘add-on’ installation or functional integration. The integrated Teves anti-skid system is presented with special attention to a three-circuit configuration including ‘dynamic’ brake circuits. Different safety levels of electronic concepts compared to the advanced Teves approach, and the application of microprocessors are discussed.

The addition of anti-lock control to vehicle braking systems represents a considerable increase in complexity in design, development and manufacturing. Related to these three activities there is much to be learned from laboratory and prototype vehicle test programmes. When vehicles are in the hands of drivers who are representative of customers and operate in the real environment, however, there is a variety of valuable lessons to be learned about the acceptance and the acceptability of a system, both in relation to the vehicle and to usage by people who are not conditioned by their employment as vehicle or brake engineers. This paper discusses some of those lessons.

Requirements for certification of composite materials used in sailplanes and powered sailplanes, as issued by the LBA (Luftfahrtbundesamt), the airworthiness authority of the Federal Republic of Germany, are reviewed. As an example of the certification procedure the fatigue life test of a CFRP Nimbus wing conducted at the DFVLR (German Aerospace Research Establishment) is outlined. Considering the fact that the certificated lifetime of 6000 hours for gliders is not long enough, a possible way is shown for getting more comprehensive general information about the fatigue behaviour of composites and for achieving higher design allowables in an acceptable time by means of structural tests.

Traditionally British Rail has used experience and sound engineering practice to ensure reliable traction and rolling stock. In-service reliability has been measured in terms of frequency of train delays in traffic. Availability is measured in terms of the number of vehicles available for service at a fixed time each day. Service problems are reported to the design authority at periodic service problem meetings.

Modern traction and rolling stock specifications call for higher petformance to be obtained within tighter cost, size and weight constraints. To meet these demanding specifications, new system designs of increasing complexity have to be adopted. This has resulted in an increased engineering risk that the performance specifications will not be met.

To ensure that reliability and availability remain acceptable, it is becoming increasingly necessary to use reliability modelling and assessment techniques. These are used from initial concept, throughout the design phase, and during the operational life of the equipment.

This paper outlines some of the basic techniques which are available to assist in the solution of today's service problems and the design of tomorrow's vehicles. The application of these techniques will be illustrated by examples.

The 1986 Railway Division Chairman outlines the problems facing the railways because of the decline in passenger and freight traffic over the past thirty years, and expresses his views on the contributions that engineers can make towards a strategy for recovery of the railways' market share. He gives details of how costs may be reduced in design, construction and maintenance of track, locomotives and rolling stock and how service to the customer may be improved.