The influence of wood hardness and logging operation on coupling forces exerted by lumberjacks during wood harvesting

Abstract Petrol chain saws commonly used in forestry cause mechanical vibration, which may lead to the development of non-specific disorders in upper extremities of the chain saw operator, referred to as hand-arm vibration syndrome (HAVS). Progress of HAVS depends on the intensity of mechanical vibration transmitted throughout the body, which is directly proportional to coupling forces applied to the vibration tool. The aim of the study was to measure coupling forces exerted by lumberjacks on chain saws and find correlation between force magnitude, hardness of cut wood and kind of logging operation. Coupling forces exerted by workers with right and left hands were measured by means of hydro-electronic force meter. All measurements were done during harvesting wood in real work conditions. Maximal temporary forces exerted by woodcutters reached 275 N. The smallest average forces of 27 N were registered while limbing. During felling and cross-cutting chain saw operators exerted larger forces, reaching 50 N. The findings of this study suggest that coupling forces used by woodcutters during logging depend on wood hardness and kind of logging operation. Relevance to industry This study shows the relationship between coupling forces, wood hardness and technique of cut which are further expected to enhance our knowledge on the assessment of vibration exposure. Nowadays, understanding how changes in harvesting technique affect the magnitude of coupling force, should lead to improvements in ergonomic design of the tool and the workplace.