Cable yarding is an inherently expensive extraction technology, but the mainstay for mountain forest management. Fuel cost represents a considerable share of total harvesting costs. Energy-recuperating, electrical slack-pulling carriages (EC), which recuperate energy during lateral yarding and store it as electrical energy in super-capacitors for powering slack-pulling during the subsequent yarding cycle have emerged only recently. Fuel consumption of cable yarding is expected to be lower when ECs are employed compared to working with conventional, diesel engine-powered slack-pulling drive (DC) carriages. To determine if reality matched expectations, a time and motion study was conductedduring which fuel consumption was extracted from the engine control systems using custom-made dataloggers for an uphill whole tree yarding operation in Austria. Average productivity was 21.9 m 3 per productive system hour excluding delays (m 3 PSH 0 −1) at 0.89 m 3 average tree volume and 58.4 m average yarding distance. Productivity was modeled as a function of average tree volume, yarding distance and lateral yarding distance. Average fuel consumption was 1.27 ± 0.97 l m −3 (DC) and 0.88 ± 0.56 l m −3 (EC). In the DC treatment, the carriage engine accounted for 9% of the total fuel consumption. Modeling revealed that fuel consumption depended on average tree volume, yarding distance, lateral yarding distance and carriage type as originally postulated. The latter effect interacted with that of average tree volume and EC's advantage in fuel consumption was limited by a break-even average tree volume. In conclusion, the EC has the potential to improve profit margins in small-tree operations through lower fuel consumption.

Purpose of Review Carriages are an integral component of cable yarding systems that are used to harvest timber on steep terrain. They provide the mobility component by allowing a payload to be pulled along a skyline that spans a harvest setting, as opposed to a brute force pulling a load along a slope. While yarder machinery and cable yarding systems are extensively studied and reported, this paper provides a first detailed review of recent developments in carriage technology. Recent Findings There has been significant development in carriage technology in the last decade. In addition to step changes in functionality, they are now also used as technology platforms. This includes integration of geospatial and camera technology to provide for higher levels of automation. There are clear regional drivers that have differentiated carriage development. The need for low mass, versatility, and energy efficiency has generated a demand for electric carriages in the central European market. A focus on safety has driven New Zealand designers to work almost exclusively grapple carriages that no longer need choker setters on the ground being exposed to danger. North American developments include carriages capable of larger payloads to increase productivity and off-set high operation cost. Summary Carriages have developed over time to become complex systems and provide additional capabilities instead of just providing a mobility and transfer mechanism within the yarding systems. By integrating new technologies that provide for greater efficiency and/or automation, carriage developments will help cable yarding systems remain cost-competitive, with high safety standard and environmentally sound.

Forest road networks are exposed to damage by traffic, climate, timber harvesting and vegetation. To maintain their functionality, they must be maintained regularly. Periodical maintenance is required when the forest road surface layer is deteriorated and eroded. Well-graded material is required for replacing the forest road surface and often has to be sourced from gravel storage areas, which is costly and requires a large number of truck trips. Therefore, converting non-graded aggregate available on site into well-graded aggregate with a mobile stone crusher is considered a viable alternative.The present study was carried out during a periodical maintenance treatment at the Bavarian State Forest Enterprise and the effect of employing a mobile stone crusher was evaluated with regard to (1) forest road load bearing capacity development during a one-year period post-treatment, (2) particle size distribution of the surface layer material before and after crushing, and (3) its cost compared to other alternatives. Samples were collected pre- and post-operation for particle size distribution analysis, load bearing capacity was measured repeatedly with a light falling weight deflectometer and compared to an untreated reference section and cost of the treatment was compared to two alternatives.The mobile stone crusher was capable of reducing the non-graded to well-graded/close-to-well-graded material and particle size distributions aligned well with the recommendations for lime-water bonded surfaces. Load bearing capacity exceeded the threshold of 40 MN m-2 (Evd, elastic modulus dynamic) for primary forest roads at all times. It increased significantly after the treatment and remained on a significantly higher level throughout the following year. Absolute and relative increases were higher than on the untreated reference section. The treatment variant involving a mobile stone crusher and material available on site was substantially cheaper (5.31 € m-1) than to supply non-graded (16.29 € m-1) or well-graded (19.82 € m-1) material by truck. Material and transport costs represented 67% and 82% of the total costs in the latter two cases. It can be concluded that mobile stone crushers are capable of producing at least close-to-well-graded forest road surface aggregate and that forest road load bearing capacity can be significantly and lastingly increased at only a part of the costs of the alternatives. A maximum of cost and resource efficiency and environmental soundness can be attained when enough surface aggregate is available on site. If this is not the case, sourcing non-graded material as local as possible is the next best alternative.

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