Vibration risk evaluation in hand-held harvesters for olives

This research aims to evaluate the vibration transmitted to the hand-arm system by two electric portable harvesters, different for size and teeth features of the harvesting head. Moreover, being the bars of the two machines telescopic, they were operated at minimum and maximum length. The acceleration was measured, at different times, in two points, 1 m apart, next to the hand positions. Finally, measurements were carried out both at no load, in standard controlled conditions, and in field, under ordinary working conditions. To smooth the influence of external factors, the machines were operated by the same operator. The results showed that the greater and heavier harvesting head produced significantly higher acceleration at no load (10.7 m/s2 vs. 5.5 m/s2), and comparable acceleration at load (13.9 vs. 14.2 m/s2). On average, the vibration was significantly higher at load (14.0 vs. 8.1 m/s2). The difference between the two bar lengths was not statistically significant: 9.4 m/s2 when using the minimum length and 9.8 m/s2 when using the maximum one. Finally, the difference between the two measuring points was affected by the bar length: it was statistically significant when using the bar at its minimum length only. As far as the components are concerned, at no load the highest acceleration was measured along the bar axis for both harvesting heads (9.2 m/s2 for the greater head and 4.2 m/s2 for the smaller one). At load all the three components were comparable in the greater head (about 7.8 m/s2) whereas the x component was predominant in the other one (11.4 vs. 4.8 (y) and 6.6 m/s2 (z)).