In logging by construction crane, time studies have been carried out by observing the crane operator and the assistant hooking the load. The study methodology used was the progress-time method where time and work phases are recorded at the end of each work situation. The duration of each phase is obtained by subtracting it from the total of the recorded times. According to the chronological and complete registration of the time needed by the work phases the sequence of operations can be made evident for further analysis; this is a great advantage compared to the zero-point stopwatch and multi-moment method. However, a disadvantage sometimes in using the progress-time method is that only one person or machine can be observed.
The equipment used to carry out the time studies was a LATSCHBACHER EG 20 computer. This hand-held computer has buttons representing the different work phases previously fed into the computer. The person responsible for the time study has to select the correct button and to press it at the end of each work phase. The moment the button is pressed the last work phase is defined and recorded together with the appropriate time involved. Subtraction, in order to get the work phase duration, is done automatically by the computer. In addition, information such as load size, method of transportation (vertical, horizontal or rehooking), type of load (long log, tree top, tree) and logging distance are recorded with the hand-held computer.
To assess the performance of logging by the construction crane it would be sufficient to observe the crane driver. However, in order to improve the sequence of operations, the work of the assistant hooking the load has to be studied, as well, particularly if the observer next to the crane is not able to see neither the trees or assortments nor the assistant at the felling site due to the height of young trees forming the natural regeneration; therefore the observer is not able to classify the causes of delays and interruptions. The recorded data are transmitted by connecting the hand-held computer to a personal computer whereby the data could be prepared to run different statistical procedures thereafter.
Production figures in logging are based on the measurement of the mid-diameter and the length of transported assortments or trees immediately after their logging by construction crane. Consequently, every calculated load volume should be related to the corresponding cycle time in order to assess logging performance.
The site characteristics are based on the measurements of the last forest taxation.