Perry Niál T., MSc

In some specific yarding situations ground contact needs to be reduced to an absolute minimum. In such cases, a double-hitch system can serve as an alternative to helicopter logging. In the present investigation, a cable yarding operation using double-hitch carriages for selective thinning in intermediate slope was accompanied by a time and motion study to better understand the working steps and resulting productivity of cable yarding in this unconventional situation. The main aims were to develop a model that can be used to estimate the productivity of comparable yarding operations before their implementation, and to quantify the additional effort relative to the use of a cable yarder with a single-hitch carriage. The results indicated an overall productivity of 5.69 m3ob per productive system hour including delays of up to 15 minutes (PSH15), leading to yarding costs of 104.40 € (m3ob)-1 (in addition to costs for installation and felling). Compared to a system with a common single-hitch carriage, the inclusion of a second lateral yarding stage increased time and cost, contributing 13.30 € (m3ob)-1. Key factors affecting productivity were payload size, number of load pieces, and terrain difficulty, while yarding distances had minimal impact. Compared with traditional yarding, double-hitch operations were less productive and more costly, but they can still be considered a suitable alternative to helicopter logging in sensitive areas.

In some specific yarding situations ground contact needs to be reduced to an absolute minimum. In such cases, a double-hitch system can serve as an alternative to helicopter logging. In the present investigation, a cable yarding operation using double-hitch carriages for selective thinning in intermediate slope was accompanied by a time and motion study to better understand the working steps and resulting productivity of cable yarding in this unconventional situation. The main aims were to develop a model that can be used to estimate the productivity of comparable yarding operations before their implementation, and to quantify the additional effort relative to the use of a cable yarder with a single-hitch carriage. The results indicated an overall productivity of 5.69 m3ob per productive system hour including delays of up to 15 minutes (PSH15), leading to yarding costs of 104.40 € (m3ob)-1 (in addition to costs for installation and felling). Compared to a system with a common single-hitch carriage, the inclusion of a second lateral yarding stage increased time and cost, contributing 13.30 € (m3ob)-1. Key factors affecting productivity were payload size, number of load pieces, and terrain difficulty, while yarding distances had minimal impact. Compared with traditional yarding, double-hitch operations were less productive and more costly, but they can still be considered a suitable alternative to helicopter logging in sensitive areas.