the design and development of suspended handles for reducing hand-arm vibration in petrol driven grass trimmer

the portable petrol driven grass trimmer is identified as a type of machine whose operator can be subjected to large magnitude of hand-arm vibration. these vibrations can cause complex vascular, neurological and musculoskeletal disorder, collectively named as hand-arm vibration syndrome. the vibration total level on the handle of grass trimmer of 11.30 m/s² was measured, and it has reached the exposure limit value of 5.0 m/s² for daily vibration exposure a(8). new suspended handles were designed to reduce the vibration level. three different prototype handles with rubber mounts were designed. handles were made of different materials, and the distance of rubber mounts were varied. from the study, it was observed that not all the handles with rubber mounts were effective in reducing hand-arm vibration. the reduction of vibration depended on the handle material and distance installed between rubber mount and vibration transmissibility of handle-isolation system. subjective ratings of perception of vibration were measured, and the results indicated that operators were not fully aware of the level of vibration. a prototype handle that is made of heavier material results in the lowest hand-arm vibration of 2.69 m/s². the new handle has significantly reduced the vibration total value by 76% compare with the existing commercial handle.