Volume 6, numéro 2, january 1995

EN :

Finnish timber harvesting changed considerably in the late 1980s and early 1990s. For example, the interaction of machines has become more important. Simultaneously, this has brought forth a new problem: a single grip harvester and a forwarder can act together well in a conventional harvesting system, but it is difficult to join a timber truck to the system. One solution could be the use of interchangeable platforms. We built a simulation model for harvesting with CADmotion software. Furthermore, thirteen stands were generated for use as input-data in the simulation by Pukkala's Conifer Stand Simulator. The time consumption and the productivity of forest machines and trucks were calculated by recently published models. In addition, the delays of machines were simulated.

In Finnish conditions the total productivity of the interchangeable platform truck is lower than that of the conventional truck. The most important reason is the transport of empty platforms between stands. The other reason is that in the conventional system the buffer can be kept appreciably larger than in the interchangeable platform system. Evidently, improvement of the truck does not improve the performance of the whole system. In the so-called hot-logging sequence, extra waiting time decreases the benefit caused by shorter loading time.

EN :

The accuracy of successive estimates of site disturbance using two ground survey methods was evaluated. Results from the point transect and grid point intercept methods were compared with those results from an intensive 1x1 m grid survey over a 4 ha study area. The point transect method, using a transect spacing of 30 m, provided the most accurate and consistent estimate of disturbance in the study area.

EN :

Eight combinations of skidder tires, ranging in total width from 0.7 m to 2.2 m, were evaluated for rut formation potential on two soils in south-central Alabama. One was a mixed pine-hardwood bottomland; the other was an upland, predominantly pine stand. Each soil/tire combination was replicated twice. Changes in soil profile after one, three, seven, and nine loaded passes were used as indices of soil disturbance. The number of skidder passes was the most significant factor influencing rut formation. The effect was linear up to nine passes on both test sites. The first pass on the upland site accounted for half the average rut depth and area. The magnitude of the displacement after one pass was related to tire width. Each subsequent pass caused a uniform smaller increment in depth and area. The magnitude of the increase was independent of tire width. On the bottomland site, however, each pass resulted in an increment in both depth and area the magnitude of which was a function of tire width. Average rut cross-sectional area on the bottomland site ranged from 0.13 m2 to 0.75 m2 for nine passes. Depth of ruts ranged from 1.7 cm to 3.6 cm for nine passes on the upland soil, and from 1.4 cm to 21.2 cm for nine passes on the bottomland soils. Soil physical properties were not affected by skidder traffic regardless of tire width.

EN :

Given that the forest industry has diversified from primarily manual extraction and processing of trees to include a wide variety of occupations and job functions, many of which require employees to make repetitive, high force motions of the hands and wrists, suggests that this group of workers may be at risk for developing carpal tunnel syndrome (CTS). To raise awareness, this paper provides an indication of the CTS risks associated with four classes of forestry occupations and gives some avoidance guidelines for the prevention of this disorder.

EN :

This paper analyses the effects of job rotation on physical effort in chain saw operations. This study was conducted in a seven-year old Eucalyptus grandis plantation harvested with a short-wood clearcut system. A practical application of ergonomie principles was utilized, considering heart rate as the method to evaluate the heaviness of work. Data were collected in a situation where the chain saw operator and his assistant rotated primary tasks to reduce physiological workload. Piling logs was the most demanding activity for the assistant, while the chain saw operator primarily is exposed to chain saw noise and vibration. Rotating jobs on this situation did not significantly reduce the total physiological workload on saw operators.