In an effort to reduce the costs of first thinnings in Finland, the S. Pinomaki Ky company has developed a concept that combines the harvesting and forwarding functions on the same machine. This concept could be of interest in situations with low annual volume requirements, scattered and small harvest blocks, and limited capital. This study compared the productivity, cost, and operational feasibility of this concept with those of a traditional two-machine cut-to-length (CTL) system based on a harvester and a forwarder.
Machine & working method
To operate within a first thinning prescription using a single machine, the machine design includes the ability to open the forwarding trail ahead of the machine and to work on both sides of the machine; the goal was to enable a spacing of at least 20 m between trails. To achieve this, a Pika 728T forwarder was modified to enable its loader to reach over the cab; the result was 4 m of reach ahead of the machine and 10 m to each side (Figure 1).
A Pika 300 harvester head was modified to enable both processing and loading functions with the same attachment. The head features continuous 360[Symbol Not Transcribed] rotation and a loading grapple that does not interfere with the delimbing and bucking functions when fully opened. The head is small (350 kg, 35-cm capacity) and is thus limited to thinnings of stands with small stems. An optional remote-control measuring system controls the length of the logs produced. (This device was not present on the head during the study.)
The harvester-forwarder works in two phases (Figure 2). First, the machine travels into the block, harvesting trees in its path and opening up a 4-m-wide trail. Some selective harvesting to the sides can also be done. In this phase, no logs are loaded into the bunk, although a small base load can be picked up to make the machine more stable. When the machine reaches the end of the block, it turns around and returns to roadside. As it moves, it harvests selectively on both sides of the trail and deposits processed logs on top of existing piles. When processing is complete, the operator loads the piled material into the forwarder's bunk. When the bunk is full, the forwarder proceeds to roadside, where it unloads the logs in the same way as traditional forwarders.
Productivity studies
Metsateho studied the combination machine working in first thinnings of pine stands and mixed woods in Finland in early 1997. Tree size during the study ranged between 0.041 and 0.134 m[Symbol Not Transcribed]3, and averaged 0.081 m[Symbol Not Transcribed]3. Volume removal varied between 40 and 89 m[Symbol Not Transcribed]3/ha, with a residual basal area of between 13 and 19 m[Symbol Not Transcribed]2.
During the productivity study, the harvester-forwarder spent 42% of its time harvesting, 46% of its time forwarding, and the remaining 12% of its time performing miscellaneous activities. Reduced travel times represent one benefit of this approach, as travel time for the harvesting phase is combined with some of the forwarding travel. However, loading times were slightly longer than with standard forwarders because the harvester head was somewhat less effective than a standard forwarder grapple-loader.
In addition, the combination machine required 19% more harvesting time per tree (for the same stem size) than a standard single-grip harvester. This difference resulted from the smaller capacity of the Pika 300 head, the lower output capacity of the machine's hydraulics, and the reduced visibility afforded by a forwarder cab compared with that from a harvester cab. With larger stems (15 cm DBH or greater), the productivity difference between the traditional harvester head and the modified Pika head increased.
As is the case with most harvesting machines, stem volume had the biggest impact on productivity of the harvester-forwarder; stand density and extraction distance had a smaller effect. Figure 3 illustrates the overall productivity of the machine as a function of tree size for a standardized extraction distance of 250 m and a stand density of 888 stems/ha. The productivity curve is flatter than would be expected with conventional single-grip harvesters, mainly because about half of the productive time was dedicated to forwarding functions, and this phase was relatively unaffected by tree size.
Total direct harvesting and extraction costs were compared for the harvester-forwarder and the traditional two-machine system. Since the harvester-forwarder is not yet a proven system, conservative estimates were used throughout the comparison to underscore the uncertainty associated with its new technology (for example, a 70% utilization rate was used). The total cost for the two systems as a function of tree size is illustrated in Figure 4.
The results showed that with tree sizes of less than 0.15 m[Symbol Not Transcribed]3, the combination machine was a cheaper alternative than the two-machine system in thinning operations. This advantage comes from reduced travel requirements and the more efficient utilization of boom movements that results from combining processing and loading functions. With larger trees, the greater processing capability of traditional heads makes the two-machine system more competitive.
Conclusions
Pinomaki's combination machine appears to represent a promising option for thinning operations with stem sizes below 0.15 m[Symbol Not Transcribed]3. Some development is still needed, such as increasing the capacity of the head and the boom, and improving visibility from the cab to facilitate opening the stand ahead of the machine. The contractor enjoyed operating the machine during the study. The variability of the tasks to be performed increases job satisfaction and motivation, which in turn probably increases productivity.
In Canada, the combination machine could represent an interesting alternative to the conventional two-machine system in commercial thinning or in the harvesting of scattered cut blocks, as well as for contractors working with annual volumes that are too low to cover the capital costs of a full two-machine system.
Risto Lilleberg is a researcher with Metsateho in Helsinki, Finland. Jean-Francois Gingras is supervisor of FERIC's Wood Harvesting Group in Pointe Claire, Que.
* This article summarizes a report by Risto Lilleberg of Metsateho in Helsinki (Metsateho is FERIC's counterpart in Finland) on the Pika 728T combination harvester-forwarder machine. This new version of an old concept is under development in Finland, and may have some applications in Canada. In fact, one North American forwarder, the Timbco TF815, is already well suited to this application, as it has a full 360-degree loader operating range. The concept was introduced by feature writer Bruce McCallum in an earlier issue of Canadian Forest Industries.
Figure 1. Loading times were slightly longer, as the harvester head was less effective than a dedicated forwarder loader.
Figure 2. The two work phases with the combination machine.
Figure 3. Harvester-forwarder productivity (m[Symbol Not Transcribed]3/hour) as a function of stem size.
Figure 4. Comparison of direct harvesting costs for the harvester forwarder and a conventional harvester plus forwarder system. (Note: 1 FIM = C$.27)
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