A survey of thirty-nine (39) industrial forest engineers was conducted to provide guidelines as to what harvesting system is best suited to specific stand and topographic variables when extracting streamside timber. The advantages and disadvantages of the operational characteristics of the standard highlead spar, mini spar, slackline, grapple yarder and rubber tire skidder are discussed both in terms of site disturbance and wood debris in British Columbia Coastal streams. Productivity and cost data are analyzed for the standard highlead spar, grapple yarder and rubber tire skidder for three selected streamside conditions. The extra cost incurred by the forest sector to comply with stream protection measures requested by fisheries personnel for pre and post harvesting treatments is also presented. Findings indicate that specific topographic and timber conditions, plus the limitations of each harvesting system dictate the selection of the system when logging adjacent to small British Columbia Coastal streams. The grapple yarder is shown to be the most cost effective and efficient system for streamside timber harvest and stream debris management. The stump to dump productivities for the highlead spar, grapple yarder and rubber tire skidder are found to differ. For the three terrain conditions cited, the grapple yarder is shown to be most productive, while the rubber tire skidder is the least costly. Stream protection costs for fisheries concerns were found to be a substantial extra cost to the forest sector. Debris clean-up costs in particular, ranged from $3.00 to $15.00 per lineal metre of stream. The recommendations of the survey respondents and current literature all clearly demonstrate that each area to be harvested having fish values must be dealt with on a site specific basis. / Forestry, Faculty of / Graduate

Maintenance, failure, and repair data on three types of feller-bunchers were analyzed. The data was tested for trends in time between failures as a function of time; time-between-failure and time-to-repair distributions were compared; the effects of changes in reliability, maintainability, and maintenance were analyzed; and a listing of reasons for failures was compiled. Four different cooperators supplied information on 32 feller-bunchers covering 41,300 operating hours that included 1814 failures. The time between failures (TBF) does decrease with machine age with the possible exception of an increase when the machine is first put into service. The TBF seemed to decrease rather rapidly during some initial operating period after which they still decreased, although at a much lower rate. During this subsequent period some machines exhibited a seasonal fluctuation, longer TBF in the summer and shorter in the winter. There were no significant differences in TBF among the three types of feller-bunchers. The greatest amount of variability occurred among machines of the same type. A comparison of times to repair (TTR) indicated that the type 2 machines had shorter TTR than the types 1 and 3 which were the same. Most failures of the shear were minor failures involving only replacing hydraulic fittings and hoses, shimming the cutting blades, or packing a cylinder. Because these are common malfunctions, parts were available and repairs did not require extended periods of time and in many cases could be performed by the operator. Failures of the carrier, on the other hand, covered a wider range. Because of this there were times when the part was not available and the repair usually required the attention of a mechanic. Therefore, failures of the carrier are more critical than failures of the shear. An increase in TBF does increase availability; however, the magnitude of the effect decreases as the TBP increases. There is definitely a point of diminishing returns. However, the longer the average repair or delay time the more pronounced the effect of the TBF. For all three types of feller-bunchers, the point of diminishing returns was less than an average TBF of 40 hours. Unlike TBF, there is a linear relationship between availability and downtime due to active repair or delay time. And, the shorter the TBF the greater the effect. The effect of service time is to decrease the effect of the other variables. As the number of failures increase the amount of service time decreases because there will be fewer services. Conversely, as the number of failures decreases the amount of time the machine is down for service increases. The most common cause of failure for all three types of feller-bunchers was the hydraulic system, accounting for 41.4 percent of all repairs. Other results indicate that a mechanic should have an adequate knowledge of hydraulics and welding. / Ph. D.

This study investigated the potential use of wide skidder tires for forest harvesting operations on steep slopes. During the summer of 1984, field tests were conducted to compare the performance characteristics of 24.5-32 and 66-43 rubber tires on a JD-640 grapple skidder loaded with tree length material. The skidder was operated on 20%, 25% and 30% slopes on Piedmont soils near Rome, Georgia. Video recorders were used to document the field measurements and observations of machine travel time and wheel slip over defined courses. Soil compaction was evaluated by comparing soil cone penetrometer readings taken in the wheel tracks of the test lanes to those taken in undisturbed adjacent areas. Skidder lateral stability was analyzed using the mathematical model developed in this study. Based on the results of statistical analyses of the data and field observations obtained under the test conditions, the skidder equipped with wide tires generally attained higher average speeds, tended to cause less wheel slip, resulted in smaller increases in soil cone penetrometer readings, and had significantly greater stability on sideslopes than the skidder equipped with the narrow tires. The stability model developed in this study predicted the critical sideways tipping angle for a JDâ 64O grapple skidder to be approximately 32° when fitted with the 24.5-32 tires, and 44° when fitted with the 66-43 tires. / Master of Science

A production and cost study for the Koller K300 skyline yarder operating on an Appalachian timber sale was undertaken to document the yarder’s performance, to identify predictors of yarder performance, to evaluate the impact of corridor dimension on machine productivity, and to estimate direct harvesting costs. The average yarding cycle lasted 5.10 minutes and produced 36.1 cubic feet of timber. Lateral yarding consumed an average of 59 percent of the yarding cycle and included 71 percent of the operating delays observed. Log hangups account for 59 percent of the operating delays. Reliable prediction of the yarding cycle time is difficult due to wide variability in the observed times. The best model found for predicting the duration of the yarding cycle uses yarding distances and lateral yarding distance as independent variables. The lateral yarding element is the least predictable element of the yarding cycle. Simulation analyses were used to investigate the effects of changing corridor dimension on average hourly yarding productivity in light of machine setup time. Corridor widths of 52 feet resulted in significantly less production than widths of either 104 or 208 feet when yarding road changes were assumed to require two hours. Corridor lengths of 208 feet were significantly less productive than lengths of 416 or 624 feet. No significant difference in productivity was found for the three corridor lengths when road changing time was reduced to one hour. Again, the 52 foot corridor widths were less productive. Estimated direct harvesting costs (on board truck) are given for two system configurations and three utilization levels. The estimates range from $22.21 per cord to $37.14 per cord. / M. S.

M.S.

Study objectives were 1) to identify successful mechanized thinning and prelogging systems currently operating in the South, 2) to document system characteristics contributing to their success, and 3) to determine which factors affect levels of residual stand damage from thinning operations. The first objective was accomplished by a South-wide industry survey. The latter two objectives were realized through in-depth field studies of selected systems. The survey indicated three system types used on small-tree operations. Feller-buncher/grapple skidder/hydraulic loader systems comprised the majority of operations described. No predictable relationships between system type and tree size were apparent, so examples of the most common type were chosen for detailed study. Three thinning and three prelogging systems were selected, covering a range of ownership patterns and physiographic regions. Information was obtained pertaining to each system's application; crew organization and background; equipment spread and descriptions; performance; and special considerations provided by landowners or timber buyers. Residual stand damage cruises were conducted at each thinning operation's job site. Case-by-case analyses and comparisons between systems based on economic and productivity criteria resulted in a number of recommendations. These suggestions represented system characteristics seen as keys to the success of the operations studied. The recommendations focused on desirable contractor and crew characteristics, equipment selection decisions, job layout, minimization of residual stand damage, and methods of landowner/timber buyer support for small-tree operations. / M.S.

In order to assess the potential of increased mechanization of harvesting functions in Nepal, surveys and field of present system were made to provide a basis for evaluation. From this information the cost of production of manual harvesting functions were compared to the cost of mechanized functions. The analyses of cost for mechanized functions were made using a mathematical model to predict the cost of production per cubic feet. The analysis predicted that: Cost of production in felling, bucking, and limbing by chainsaw is made economical than the manual operation by axe and cross-cut saw. Skidding of logs by a rubber tired cable skidder (JD 440 C) is costly. However, its potential can be considered for the hill region because a manual skidding is difficult there. A farm tractor could be economical for a skidding distance of 200-300 feet in the terai. The cost of loading and unloading of logs with a hydraulic knuckle boom truck mounted loader (Prentice 110) is economical. Implementation of mechanized harvesting will be feasible only, if arrangements are made to train operators, provide supplies and service for machine, provide for unemployment, improve machine utilization, and generate the capital needed for equipment purchases. / M.S.

The purpose of the study was to define the characteristics of tree-length skidding on the Lower Coastal Plain of Georgia. The objectives were: 1) to document skidder performance based on speed and tire slip, 2) to determine the effects of skidding on soil physical properties, and 3) to develop recommendations to minimize the impact on soil properties while maintaining skidder performance. A Franklin 170 grapple skidder was operated in second gear under moist (19% moisture content) and wet (31% moisture content) soil conditions using 28L-26, 67x34-25, and 73x44-32 tires. One, three, nine, and 27 passes were tested. The skidder was also operated in third gear with the 73x44-32 tires under the wet soil condition. With moist soil conditions skidder speed and tire slip were not affected by tire size or the number of skidder passes. Tire size did not influence soil properties. It was recommended that skidding be dispersed to avoid making more than nine passes over any particular soil area because the research indicated that repetitive passes resulted in a cumulative decrease in non-capillary porosity and an increase in bulk density. During wet conditions, wheel slip increased, skidder speed decreased, and rut formation increased with smaller tires, an increase in the number of skidder passes, and second gear operation. Operating the skidder in third gear with the 73x44-32 tires was beneficial to skidder performance and a reduction in rutting. Recommendations were to disperse skidding to maintain productivity and minimize rutting. / Master of Science

M.S.

Recent advancements in timber harvesting systems analysis have been almost exclusively simulation based. A similar degree of effort in developing analytic models has been conspicuously absent. That part of timber harvesting analysis where simulation plays its most vital role is the study of machine interactions. The importance of machine interactions lies in determining the proportions of delay, idle and productive time for the interacting machines. This in turn, is important for balancing productivity so that no single component of the interaction is accumulating excessive amounts of delay or idle time. The objective of this study was to determine the feasibility of applying Markov process theory to the analysis of timber harvesting systems and components. Through modeling the interaction between a fixed location slasher and a grapple skidder, it is shown how a Markov model can be used to obtain proportions of delay, idle and productive time. Unlike the statistical solutions derived from simulation models, the Markov model improves upon this by providing an analytic solution. The Markov model also avoids the problems of correlated output data from simulations by explicitly recognizing that any possible future state is dependent only on the current state of the system and is conditionally independent of the past history of the system. The methodology for building a Markov model requires dealing with only two probability distributions, the Erlang and mixed Erlang, for modeling time based activities (such as cycle times) of the interacting machines. These probability distributions in turn, provide the necessary data for developing a system of algebraic equations for solving the Markov process model. While this is the first step in applying stochastic process theory to timber harvesting analysis, the results of this study indicate that the technique has considerable potential for application in timber harvesting system modeling. / Ph. D.