Nodal control of grass trimmer handle vibration

Abstract

Imposing node technique is applied to the grass trimmer shaft in order to achieve very low vibration (node) at the handle location. The optimum tuning frequencies of the two tuned vibration absorbers (TVAs) attached at 0.74L and 0.85L along the shaft of the grass trimmer are determined using the imposing node technique. Transverse deflection, experimental modal analysis and operating deflection shape analysis of the grass trimmer were carried out, and the results indicated that nearly zero deflection (node) was induced at the position very close the loop handle location. Moreover, the vibration along the segment of the shaft (0.70L–0.94L) was also found to have relatively small amplitude. The TVAs were found to have best performance with 71% reduction on the frequency weighted rms acceleration at the loop handle and 72% for the rear handle. The results from the experimental modal analysis and operating deflection shape revealed that the presence of the two TVAs has successfully reduced the large deformations of the loop and rear handle where the node was shifted nearer to the handle location. The effects of TVAs were also evaluated during the field test involving grass trimming operation and subjective rating. The results indicated that average reduction of frequency-weighted rms acceleration was by 25%, 69%, 17%, 58% in Xh-, Yh-, Zh- axes and vibration total value respectively during the cutting operation. From the field test, subjective rating of vibration perception consistently rate better for the controlled grass trimmer. Relevance to industryLarge numbers of workers are employed to perform grass trimming job in maintenance of parks and areas with undergrowth. This paper presents the imposing node technique to control handle vibration to the lowest value.