Mechanical Feeding of Grapple Yarders

Excavator-based shovelling machines can be used on steep terrain to improve the safety and productivity of cable yarder extraction. Shovelling felled timber across to a yarding corridor limits the number of line-shifts required, and feeding the grapple carriage reduces cycle time and increases average payload. The study determined the productivity, utilization and time use of four excavator-based shovelling machines feeding a cable yarder operation using a grapple motorized carriage at four different sites in New Zealand’s South Island. The four machines were owned and operated by four different contractors, but they all worked on end-of-rotation radiata pine clearcuts. Productivity varied from approximately 25 to 100 m3 per hour, including waiting time for the grapple carriage to return, but excluding all other delays. Piece size had the strongest impact on productivity. Mean utilization was 61%. 20% of shovel worksite time was spent engaging with productive work other than feeding the grapple, such as felling, shovelling or tidying up the cutover.