Drivarens produktivitet vid lossningsarbete
During the last few years the harwarder has developed from a prototype into a market product. Holmen Skog owns two harwarders and uses two more owned by entrepreneurs. In previous studies it has been shown that the harwarder was a slow and expensive forwarder. In this study the unloading at road-site was studied. The goal was to describe the differences in time consumption between unloading two-sided or single-sided (only from side of the road) and also the difference between unloading with three and four assortments in the carrier.
In the way the study was designed, there were 31 carrier-loads to unload; 16 single-side loads and 15 two-side loads. The 31 loads were divided into 16 loads with three assortments and 15 loads with four assortments. 15 of the loads were unloaded by an experienced driver and the other 16 by an inexperienced driver. The unloading was filmed and the time was measured afterwards.
Single-side unloading means that the operator drives the harwarder in the terrain and unloads the carrier towards the road. Two-side unloading means that the operator drives the harwarder on the forest road to unload the carrier to both sides of the road.
Single-side unloading proved to take longer time than two-side unloading. With single-side unloading the average production was 71.1 m3sub/h and with two-side unloading the average production was 87.3 m3sub/h. The difference was significant (16.2 m3sub/h).
There was almost no difference in time consumption between unloading with three or four assortments in the carrier. The forwarder?s carrier was divided into two parts and there was no problem for the drivers to keep the assortments apart. The average production was
75.7 m3sub/h and 79.1 m3sub/h respectively. The difference was not significant (3.4 m3sub/h).
There was a significant difference in productivity between the drivers (30 percent). The difference in time consumption was relatively constant between the drivers. The experienced driver carried out all moments faster than the inexperienced driver.
The cost for the higher time consumption at single-side unloading was 2.3 SEK/m3sub. This cost must be compared to the cost for the repair or reinforcement of the road that was needed before two-side unloading. If the object is smaller than 1300 m3sub/h the cost of single-side unloading is less than the cost to reinforce the road. The harwarder is often used in small cuttings and for such objects it can be cost effective and the total cost can be reduced.