Abstract
Accurate predictions in forest operations can be used towards effective planning, costing, and maximizing the productivity of machines in mechanised cut-to-length (CTL) harvesting. There is a general and substantial gap in forwarder productivity data available for pine sawtimber in South Africa at present, and as the number of product assortments being harvested increase there is a need for more work to quantify the effects of extracting products of different dimensions. The aim of this study was to calculate the time consumption and productivity of two models of Ponsse forwarders (15 t and 20 t capacity) to consider and compare the effects of multiple variables including machine capabilities, product assortment, load size, extraction distance and fuel consumption. Productivity averaged at 34.08 m3 per productive machine hour excluding delays longer than one minute (PMH1) for the smaller machine, and 55.94 m3/PMH1 for the larger machine. Productivity and average log volume were strongly positively correlated. Regression models were created for each machine where load volume and extraction distance were both significant factors for predicting productivity. Average fuel consumption of the smaller machine was 15.55 l/PMH1 and 0.47 l/m3, and 20.57 l/PMH1 and 0.43 l/m3 for the larger machine. The product with the largest volume was found to require the least fuel per m3. The models developed could aid in predicting system productivity and potentially carbon emissions under similar conditions in a South African context of industrial plantation forestry.
Highlights
Mechanized cut-to-length (CTL) harvesting comprises two machines: a harvester that fells and processes trees into log assortments, and a forwarder that extracts and transports the logs to the roadside landing (McNeel and Rutherford 1994)
3.1 Time Consumption A total of 78 forwarding cycles were recorded resulting in a total of 1986 productive machine minutes, of which 36 cycles were from the Buffalo machine (1076 minutes) and 42 cycles were from the Elephant King machine (910 minutes)
It should be noted that cycle times were dependant on factors such as the distance travelled loaded and unloaded, which was highly variable based on the amount and concentration of products in the field
Summary
Mechanized cut-to-length (CTL) harvesting comprises two machines: a harvester that fells and processes trees into log assortments, and a forwarder that extracts and transports the logs to the roadside landing (McNeel and Rutherford 1994). The most common way of investigating and identifying the main factors affecting productivity of CTL harvesting is to analyse effective time consumption, from which realistic models can be developed and employed towards optimizing operations and efficiency (Nurminen et al 2006). By recording time consumption and the main factors that affect it, it is possible to establish productivity, which provides a reference point towards costing and operational planning (Nurminen et al 2006). When it comes to mechanized harvesting systems, the productivity of forwarders
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