FREQUENCY RESPONSES OF MOTORCYCLES TO STEERING TORQUE INPUTS AND TO FRONT WHEEL AND TYRE IMPERFECTIONS

An existing mathematical model of a motorcycle in free control, which is capable of explaining in general terms the small perturbation steering stability and modal properties, is extended to allow the calculation of responses to sinusoidal inputs of rider applied steering torque, and to forcing arising from dynamic unbalance of the front wheel, lateral force variations at the front tyre/road contact, and swashing of the front wheel. The various responses are presented and their practical implications are discussed. Steering torque inputs are shown to be capable of exciting the main oscillatory modes of motion when the vehicle speed and forcing frequency are appropriate. Responses to front wheel and tyre derived forcing are shown to peak when the vehicle speed is such that the front wheel rotation frequency coincides with the natural frequency of the wobble model. In this resonant condition, it is suggested that easily perceptible vibrations can occur, depending on the wobble mode damping and the degree of wheel imperfection. A design criterion for avoiding extreme sensitivity to wheel condition is suggested.

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: p. 193-200

Subject/Index Terms

Filing Info

  • Accession Number: 00387043
  • Record Type: Publication
  • Source Agency: National Highway Traffic Safety Administration
  • Report/Paper Numbers: C129/83, HS-036 355
  • Files: HSL, TRIS, USDOT
  • Created Date: Jul 30 1984 12:00AM