In this study ， we measured transfer functions of a bicycle at various experimental conditions by performing a hammering test and measured vibration at running for considering a suitable hammering test cendition． In the tests ， we focused differcnce of resonance frequency of a bicycle frame With driver and that without driven As results ， the transfer function measured at hanging the bicycle using a rubber tube ( without driver ) shows clear resonance peak and the frequency was almost same at that at running test ( with driver ) ． Therefore ， hanging bicycle without driver was clarified to be suitable experimental condition for a harnmering test ．

Bicycle is a popular vehicle for general public because of the low price and the easy maintenance, and will be more importance vehicle by the low environmental loading in the future. Improvement of bicycle ride comfort is one of important factors to increase the popularity. In this study, subjective evaluation test and reduction of bicycle vibration were performed to improve it. In the subjective evaluation, low frequency seat vibration was found to affect the ride comfort very much. Subsequently, transfer path analysis (TPA) and hammering test were performed to obtain vibration characteristic of the bicycle for reduction of the seat vibration. Through TPA, rear frame of the bicycle was found to have high influence to seat vibration than that of front side and the vibration behavior was obtained by modal analysis.For reduction of the seat vibration, a spring was inserted to the front of the seat and steel plates were attached to rear frame to increase the stiffness. As a result, the acceleration level at running condition was decreased about 10 dB by the modification, and the ride comfort was improved so much.

Bicycles are popular with the general public because of their low price and easy maintenance, and they will be an important vehicle in the future because of their low environmental load. Improving the comfort of the ride is one of the important factors that will lead to increased popularity. We attempted to increase comfort by reducing vibration, and evaluated the results with a subjective test. We determined that low frequency vibration of the seat greatly affected the comfort of the ride. We then performed a transfer path analysis (TPA) and a hammering test to investigate how the vibration characteristics of the bicycle affected the vibration of the seat. Through TPA, the rear of the bicycle frame was found to have a high influence on the seat vibration, and the vibration behavior was obtained by modal analysis. In order to reduce seat vibration, a spring was inserted in the front of the seat and, to increase the stiffness, a steel plate and bolts were attached to the rear of the frame. As a result, the seat vibration while riding was decreased by about 10 dB, and the comfort of the ride was greatly improved.

In order to expand the popu ］ arity ofthe bicycle ， improvement ofthe ride comfbr 口 s necessary ． In this study ， to improve the ride comfbrt of a utility bicycle ， subjective evaluation tests and accelerat ｛ on measurements were performed ． In the su 切 ective evaluation test ， the vibration feeling of the seat and the ride comfbrt of bicycles were evaluated by using five kinds of bicyc 】 e ． And the vibration accelerations of the seats were measur ¢ d and 丘 equency analysis was perf ( ) ed to obtain which f セ equency band has high contribution to the ride comfbrt ． As a result ，10w 丘equency vibration of the seat was clarified to have high contrlbution to the ride comfbrt Next ， the seat vibration reduction was tried． For decrease of the seat vibration ， the spring rate of the seat was reduced ． As results ， the acceleration Ievel was decreased in the nmning test and the ride comfbrt was improved ．