Influence of Loading Distance, Loading Angle and Log Orientation on Time Consumption of Forwarder Loading Cycles: A Pilot Case Study

Abstract

Fully mechanized timber harvesting systems are well established in forest operations worldwide. In cut-to-length (CTL) systems, forwarders are used for extracting logs from the stand. The productivity of a forwarder is related to site- and stand-specific characteristics, technical parameters, organizational aspects, and the individual skills of the operator. The operator’s performance during “loading” considerably affects forwarder productivity, since this element occupies nearly 50% of forwarding cycle time in CTL operations. When positioning the forwarder for loading, different loading angles and loading distances arise. Additionally, different log orientation angles in relation to the machine operating trail can be observed. Therefore, an in-depth analysis of loading conditions was conducted. The goal of this pilot case study was to explore the potential impact of different loading angles and distances, and log orientation angles, on time consumption per loading cycle in order to derive indications for more efficient work practices. Therefore, controlled loading sequences were tested on a physical Rottne-F10-based forwarder simulator with an experienced forest machine operator. Three loading angles (45°, 90° and 135° azimuthal to the machine axis) with five loading distances (3, 4, 5, 6 and 7 m), and three log orientation angles (45°, 90°, 135°), resulted in a total of 45 settings, which were tested in 10 repetitions each. The time required for a loading cycle was captured in a time study, applying the snap-back method. Results showed that all three tested variables had a significant influence on time consumption per loading cycle. Loading at an angle of 135°, and from a close (3 m) or far distance (7 m) led to especially increased cycle times. Loading from 4 to 6 m distance could be detected as an optimal loading range. Additionally, log orientation angles of 45° and 90° led to increased loading efficiency. Even if the validity of the results may be limited due to different conditions and influencing factors in field forwarding operations, these data can contribute to a better understanding of the loading element and, in particular, to productivity determining factors of forwarder work.

Positive and Negative Work Practices of Forest Machine Operators: Interviews and Literature Analysis

“…"Negative" positioning, i.e., too far a distance between the machine and the tree to be harvested (harvester), or the wood pile to be loaded (forwarder), leads to increased wear and tear of the crane elements and also to decreased productivity due to longer crane paths. This is in line with other studies which revealed that increasing loading distances can have a negative impact on time consumption per loading cycle [27], and therefore productivity. Since the loading element is the most important [23] to productivity, adequate positioning towards reducing time consumption during loading is worth striving for.…”

“…The literature search on forwarder operators showed that loading is the primary interest of the retrieved studies. [27] found log and loading angles of 45 • as most beneficial within a work range of 4-6 m for a certain machine type. Moreover, the grapple load was analyzed in another study, and the assortment pile size should match the maximum grapple load, to ensure efficient handling [4].…”

“…Sixteen studies were examined in total [4,8,24,27,[31][32][33][34][35][36][37][38][39][40][41][42]. Three out of these studies [24,31,36] were simulator-based studies, and 13 studies were conducted in-field [4,8,27,[32][33][34][35][37][38][39][40][41][42]. Simulator studies assessed more participants, whereas field studies range from 1-6 participants.…”

“…Generally, when reported, the operators that served as participants were experienced and had more than 10 years of experience. Four [4,27,33,36] out of the sixteen studies were assessing forwarder work whereas ten [24,31,32,34,[37][38][39][40][41][42] were concerned with harvester operations, a single study was concerned with a harwarder [35], which is a combined machine of harvester and forwarder. Both thinning and clear-felling operations were the focus of the research.…”

“…These work elements are divided into Driving/Crane use/Felling/Processing/Manipulation for the harvester [22] and Travel empty/Travel loaded/Loading/Unloading [23] for the forwarder, respectively. Studies suggest that the work method and the work practice of the forest machine operators are crucial for overall performance in highly mechanized timber harvesting systems [24][25][26][27]. Due to the interchangeable use in the literature of the terms work practice, work, and work method, it remains unclear how deeply work practices affect the productivity of forest machine operators.…”