Browsing by Author "Ackerman, P."
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- ItemA Southern African perspective on prevision forestry.(2005) Ackerman, P.
- ItemA comparison of two methods of data collection for modelling productivity of harvesters : manual time study and follow-up study using on-board-computer stem records(Marin Dracea National Research-Development Institute in Forestry, 2018) Brewer, J.; Talbot, B.; Belbo, H.; Ackerman, P.; Ackerman, S.Abstract. Productivity of a mechanized P. patula cut-to-length harvesting operation was estimated and modelled using two methods of data collection: manual time study and follow-up study using StanForD stem files. The objective of the study was to compare the productivity models derived using these two methods to test for equivalence. Manual time studies were completed on four different machines and their operators. Two Ponsse Bear harvesters fitted with H8 heads, and two Ponsse Beaver harvesters, fitted with H6 heads, were included. All machines were equipped with Ponsse Opti2 information system. All four operators had approximately 1 year of experience working with their respective machines. The four machines worked in separate four-tree-wide harvesting corridors, and they each harvested 200 trees. Individual tree diameter at breast height (DBH), and height measurements were made manually. Subsequently, data on the trees in each study were extracted from the StanForD stem reports from each of the harvesters. Cycle times in the stem reports were determined based on the difference between consecutive harvest timestamps. The two methods were compared in terms of their abilities to estimate equivalent measures for tree DBH, volume, and productivity. In all four cases, significant differences were found between the DBH and volume measures derived using the two methods. Subsequently, the volume measures from the manual methods were used as the basis for productivity calculations. Results of the productivity comparisons found no significant differences between the models developed from the two methods. These results suggest that equivalent productivity models can be developed in terms of time using either method, however volume discrepancies indicate a need to reconcile bark and volume functions with the high variability experienced in the country.
- ItemExcavator-based processor operator productivity and cost analysis in Zululand, South Africa(2011) Hogg, G.; Pulkki, R.; Ackerman, P.Operator impact on productivity and cost using similar processor machines was addressed in this case study. The study had two objectives: (1) determine the extent of operator productivity variation between six processor operators in a harvesting operation; and (2) determine potential cost implications associated with operator productivity variation. The study was carried out on the Zululand coastal plains near Kwambonambi. A multistem mechanised harvesting system, working in Eucalyptus grandis × camaldulensis pulpwood stands (with an average rotation length of seven years) was observed. The operators had all been operating their respective processors for 18 months; i.e. since the inception of the harvesting operation and had received similar in-house training. Time studies were carried out on the processors' cycle times, and note taken of the respective operators working the machines during the time studies. Cycle time for each machine was measured as the time between a delimbed and debarked tree length leaving the processor head and the following tree length leaving the head. The required number of observations per processor was determined by cycle time and work element time variation. It was found that operators varied by up to 58% in terms of productivity, 24% in terms of utilisation and 70% in terms of cost. The potential difference in cost between using the cheapest operator and the most expensive operator was R9.34 m -3, R4 438 d -1 and R1 384 752 y -1. © 2011 Copyright NISC (Pty) Ltd.
- ItemFibre volume losses of eight softwood clearfell harvesting systems in South Africa(2012) Ackerman, P.; Pulkki, R.A study of both fibre volume loss and related opportunity cost was performed across the South African softwood sawtimber industry to gain information on the actual utilisation of useful fibre and potential loss or gain of opportunity in terms of potential revenue from both field practices and policy. The study quantified volume losses from high stumps, felling and crosscut saw kerf, log allowances, excessive removal of merchantable wood, incorrect log trimming allocation, and utilisable wood left in-field. Eight treatments were examined: four terminated with merchandising at roadside landing and four at merchandising yards. Within the treatments, felling was either motor-manual or mechanised and compartments were classed by average compartment tree size (less than or greater than 1 m 3). Total wood utilisation was found to be 92.07%. Stumps were found to be 7 cm higher than necessary and volume losses because of high stumps were 0.79% and 0.07% for mechanical and motor-manual felling, respectively. For felling saw kerf losses, mechanical felling showed 0.92% loss, whereas motor-manual felling resulted in only 0.15% loss. Incorrect log trimming allowance provided for 0.60% loss. Excessive trimming of logs resulted in 2.02% loss. Volume lost because of crosscutting saw kerf was low at 0.20%, but tops not being extracted resulted in 2.57% loss. Using SIMSAW 6 simulations, these volume losses translated into an additional annual harvested volume of 421 722 m 3 or additional 1 278 ha harvested area, R166 million log value and R393 million net lumber value loss. Total loss was lowest (6.49%) in the average tree size class less than 1 m 3, which was mechanically felled regardless of merchandising location. For the majority of volume loss categories, motor-manual felling caused greater loss when compared to mechanical felling methods. Log trimming allowance consumed 80 604 m 3 annually. The results indicate that the human element may have a greater impact on fibre and value losses than the system choice. Further research is recommended to quantify the effect of the human element. © 2012 Copyright NISC (Pty) Ltd.
- ItemReverting urban exotic pine forests to Macchia and indigenous forest vegetation, using cable-yarders on the slopes of Table Mountain, South Africa(2003) Ackerman, P.; Talbot, B.This paper discusses some of the issues faced during the initial phases of a 12-year long project, which will ultimately result in the transformation of 53 ha of urban pine forests to a more diverse natural vegetation cover. Public sentiment, harvesting procedures and future management practices are addressed. The forests are currently managed for recreation and are a heavily utilised public amenity. Efforts have been made at every opportunity, to minimise disturbances to the recreational and biological capacity of the forest area. Public participation was encouraged at all stages, from a local to a national level. Harvesting operations were planned to make the transition from high open pine forest to mixed scrub Macchia and moist indigenous high forest as gradual, though complete, as possible within the given time frame. An aerial cable extraction system with a fixed skyline was applied in extracting the timber to minimise site impacts. Successful marketing of the timber together with the application of industrial harvesting technology meant that the project could be self-financing, which was an important prerequisite. Both public and vegetational response has been encouraging, and the inevitable, unforeseen problems and compromises, that have had to be met since project inception have been dealt with in an open and constructive participatory forum.
- ItemSouth African Forest Road Handbook Chapter 1 : Introduction Chapter 2 : Road Planning Appendixes : Glossory Equation List(2005) Brink, M. P.; Slate, J.; Ackerman, P.; De Wet, P.; Harrington, P.; Jones, D.; Shuttleworth, B.
- ItemThe future of South African contracting: Outsourcing in South African Forestry plantations. In Focus on: Labour inspection in forestry.(Forworknet Update, ILO, Rome, 2006) Laengin, D. W.; Ackerman, P.