Motorcycle steering behaviour

The thinking behind the choice of a data recording method that will be used to gather information on the frequency responses of motorcycles is discussed. The design and development of a microcomputer based data acquisition system (including transducers and signal conditioning circuitry) is described, along with the test and data processing strategies to be used. A new theoretical model is developed which includes a frame flexibility that allows the rear wheel of the motorcycle to yaw and camber about an inclined axis. The effects of changes in axis position and stiffness are investigated, and stability results are presented for the straight-running condition. The measurement of this stiffness (and that relating to a flexibility involving the front frame) for a large motorcycle, by both static and dynamic methods, is described. The nature of the flexibility involving the front wheel assembly is examined, and conclusions are drawn regarding the validity of theoretical models and the use of appropriate stiffness measurement methods. Theoretical frequency responses of a motorcycle to steering torque inputs are calculated for the straight-running condition. An attempt is made to interpret the responses by studying the effects on them of various motorcycle parameter alterations, and comparing these with the changes in handling performance as predicted by riders' experiences with real machines. The common notion that there exists a trade-off between stability and responsiveness is examined. Two new theoretical models, each representing a motorcycle towing a type of trailer, are developed and the stability results are presented. The effects of trailer parameter variations are described and recommendations relating to the design and use of the combinations are made. A description is given of the design and development of a microcomputer controlled, modal motion simulator, which employs stepper motors driving a scale model motorcycle. The simulation strategy and software are discussed and improvements are suggested.