Abstract
Effectiveness of vibration isolation was examined on a commercially availableisolator made of Nighthart system which was applied to a rock-drill of leg-type. As the effectiveness was not so high, these handles were tried to improve by chang-ing their mechanical parameters. The vibration characteristic on them was ob-served on the vibration table and their results were explained mathematically. Thus, the isolators more or newly tentatively made were also tested on the vibration table and practically on the rock-drill. Besides, the method of mea-surement for effectiveness of the isolator was studied at the same time, namely, on spectrum difference, on attenuation measurement on the vibration table and on vibration level measured with a vibration level meter for portable vibrating tools (JIS-C-1511).
