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The stability factor is widely used for four-wheel vehicles as an index representing the turning performance of a vehicle. Stability factor for two-wheel vehicles has been proposed as an indicator of cornering performance from the same way of thinking. In line traceability evaluation as a sensory evaluation item of motorcycles, the expressions of understeer and oversteer are sometimes used, but the relation with stability factor for two-wheel vehicles has not been investigated. In this paper, a test in which the slip angle characteristics of the front and rear tires were varied using a riding simulator was conducted, and the correlation between the stability factor and the rider evaluation was investigated to derive an index showing the line traceability.

This paper describes the development of a new concept two-wheel steering system for realizing motorcycle motion control. By considering the whole of the main frame as the rear-wheel steering axis, it was possible to move the rear-wheel steering system from the conventional installation position at the rear arm to the head pipe. As a result, the developed two-wheel steering system is both lightweight and compact. This two-wheel steering system was installed in a motorcycle, and starting and stopping tests were carried out with two people riding on the motorcycle. The test results confirmed that the two-wheel steering system is capable of changing the motion characteristics of the motorcycle in actual riding. Furthermore, by calculating the equivalent wheel alignment of this system, this paper also theoretically demonstrates that these changes in motion characteristics are caused by changes in caster and trail.

This paper presents a practical simulation model of the rubber V-belt CVT which is widely used as a low cost driveline element for small displacement motorcycles. The characteristic of this CVT is determined by the axial force balance between driver and driven pulleys, and the elastic force of a rubber V-belt. Because these axial and elastic forces are calculated by the kinematic and FEM analysis, a large-scale simulation model which costs long execution time for the calculation is needed to estimate the characteristic of CVT. This calculation uses the one-dimensional simulation model built up with MATLAB and SIMULINK environment, so that it was possible to get the calculation result with relatively low execution time. The elastic deformation of the rubber V-Belt was calculated by a simple spring model which was verified by experiments and FEM.

Dry centrifugal clutches used in conventional scooters occasionally suffer from judder, a problem that is extremely time consuming and expensive to solve. In order to study the judder phenomena, an experimental analysis was performed on a 125cc scooter. Numerical simulations were also performed to verify the experimental analysis results and to elucidate the principle of the judder. The results of this analysis show that dry centrifugal clutch judder can be modeled as torsional self-exited vibration of the drive train caused by the friction characteristics of the clutch, and that tire characteristics are also a contributing factor. These results correspond to previous experimental findings and countermeasures.

An original multi-body dynamics simulation program for reciprocating engine system with elastically deformable piston skirt was developed in order to understand and examine the secondary motion of piston. This program uses specialized equations of motion using only the rotational degree of freedom of each components taking the valiation of rotating speed of crank into account. In order to validate the practical use of this program, the calculations were compared with the measurements on the piston motion of a two-stroke engine for motorcycles and a four-stroke engine for automobiles, and good agreements were obtained between them.