[The vibration of the handle-bars of a motorcycle in running on the paved road (author's transl)].

Lately, in our country, daily motorcycling mail deliverers suffered from vibration hazards have been increasing. The vibration level of the handle of motorcycles was measured in order to evaluate its hazardous effects. The tested motorcycle with a 90 cc engine was selected among many motorcycles for daily use. Running test was made on the chasis dynamometer and asphalt roads. Following results were obtained. 1) The direction showing the maximum value of vibrations acceleration is in other directions than, X, Y, Z of ISO (International Organization for Standardization). 2) The maximum vibration acceleration level exceeds the exposure guidelines of ISO and its frequency is an accordance to the engine speed of the motorcycle in running. 3) The levels in the frequency ranges from 6 to 20 Hz and from 50 to 100 Hz are liable to induce vibration hazards. 4) The stronger the gripping power, the more the vibration acceleration level in the frequency range of 6-20 Hz and, on the contrary, the vibration acceleration level decreases in the range of 50-100 Hz. 5) The rubber grips of this motorcycle are not effective for abating the vibration on the frequency spectrum less than 125 Hz or 200 Hz.