Log Skidder Research Articles

Modeling the fuel consumption of forwarders based on different log sizes and forwarding distances

The aim of the proposed study was to show the fuel consumption of various log skidders and to create models for estimating the fuel consumption for different forwarders operating in cutting areas with different tree size characteristics. Production tests of the forwarders' operation at various cutting areas have been carried out. In experimental studies, forwarders from different countries were used. In particular, forwarders: Amkodor-2682 (Belarus), Komatsu 840 (Japan), TB-1M-16A (Russia).To implement the experiment and estimate the fuel consumption by forwarders, a volumetric method of replenishing the fuel tank at the end of the machine's working cycle was chosen. As a result of the performed experimental studies, the mathematical models for calculating the fuel consumption of forwarders on the dimensional characteristics of trees and the distances of log forwarding have been substantiated. They are necessary for estimating fuel consumption under different operating conditions of forwarders. The results were obtained with a confidence level of 0.95. The coefficients of determination for forwarders: Amkodor-2682, Komatsu 840, TB-1M-16, were 0.81, 0.80 and 0.84, respectively. This shows a high proportion of the influence of the dimensional characteristics of the object of labor on the fuel consumption of machines. The use of the developed mathematical relationships will facilitate the planning and calculation of the operating costs of the forwarding equipment.

A model of crack opening stresses in variable amplitude loading using smooth specimen fatigue test data for three steels

Crack growth under variable amplitude loading can be largely explained through changes in fatigue crack closure and crack opening stress. This paper presents a methodology for modeling changes in crack opening stress level and fatigue damage using data derived from periodic underload fatigue tests of smooth specimens for three steels with diverse hardness (soft, medium, and hard). The predicted crack closure stress levels are modeled under constant and variable amplitude loading (SAE Log Skidder History) and agree well with experimental measurements made with a high magnification microscope.

Prediction of crack opening stress levels for 1045 quenched and tempered steel under service loading spectra

ABSTRACTThe opening stresses of a crack emanating from an edge notch in a 1045 quenched and tempered steel specimen were measured under two different Society of Automotive Engineers (SAE) standard service load histories having different average mean stress levels. The two spectra are the Grapple Skidder history (GSH), which has a positive average mean stress, and the Log Skidder history (LSH), which has a zero average mean stress. To capture the behaviour of the crack opening stress in the material, the crack opening stress levels were measured at 900X using an optical video microscope, at frequent intervals for each set of histories scaled to two different maximum stress ranges.A crack growth analysis based on a fracture mechanics approach was used to model the fatigue behaviour of the steel specimens for the given load spectra and stress ranges. Crack growth analysis was based on an effective strain‐based intensity factor, a crack growth rate curve obtained during closure‐free loading cycles and a local notch strain calculation based on Neuber's rule.The crack opening stress (Sop) was modelled and the model was implemented in a fatigue notch model, and the fatigue lives of the specimens under the two different spectra scaled to several maximum stress levels were estimated. The average measured crack opening stresses were between 6 and 12% of the average calculated crack opening stresses. In the interest of simplifying the use of Sop in design, the average Sop was correlated with the frequency of occurrence of the cycle reducing the Sop to the average crack opening stress level. The use of an Sop level corresponding to the cycle causing a reduction in Sop to a level reached once per 10 cycles gave a conservative estimate of average crack opening stress for all the histories.

Developing a Radio-controlled Log Skidder with Fuzzy Logic Autonomous Control

This article presents the development of a small, radio-controlled (RC) log skidder and also discusses the results of a preliminary investigation into using fuzzy logic for autonomous control of the skidder. Small skidders can reduce the environmental impact of logging and help improve timber stands. With previous small skidders, the operator walked in front of the skidder and reached back with one hand to operate the controls on a handle. The RC skidder allows the operator to be removed from the immediate vicinity of the skidder, thus making a safer operating environment. Field trials of the RC skidder were conducted and are discussed.

Another Look at Skidder Ride Vibration…

Abstract Whole-body vibration data from recent tests on several log skidders are presented. Weighted RMS (root mean square) and RMQ (root mean quad) values are compared to FERIC results of 1987. The PSD (power spectral density) of the vertical motion of the seat base is compared with the PSDs currently defined in ISO and SAE Standards for the evaluation of seat suspensions on earthmoving equipment and agricultural tractors. This paper suggests the adoption of a seat performance test such as those contained in ISO 7096/SAE J1385 for earthmoving equipment, or in ISO 5007/SAE J1386 for agricultural tractors. Seat suspensions capable of meeting the requirements of such a test will attenuate the vibration at the frequencies most prevalent on skidders, and should significantly improve the ride on these machines.

Vibration attenuation performance of suspension seats for off-road forestry vehicles

Four different types of vertical suspension seats were evaluated in the laboratory and in the field in order to measure their adaptability for attenuating whole-body vibration in log skidders used in the forest industry. Laboratory testing first consisted of determining the static and dynamic characteristics of the seats such as the static stiffness of the cushions and suspension systems and the hysteresis parameters and damping properties of the cushions. The vibration attenuation characteristics of the seats were then measured using a laboratory test rig simulating a driver work station. The influence of amplitude of excitation and the variations in seat height on the vibration attenuation performance of the suspension seats was evaluated for sinusoidal excitations in the frequency range of 0.2–8.0 Hz. The seats were then field tested during normal skidding operations to determine their vertical transmissibility characteristics and to compare the vibration exposure that results from operating a skidder while being equipped with a suspended seat, as opposed to having an unsuspended one. There was generally good agreement between the transmissibility characteristics measured in the laboratory and in the field. The results of vibration transmissibility and exposure are helpful in identifying one of the suspension seats as being the most appropriate for attenuating vertical whole-body vibration on skidders, while conforming at the same time to the basic dimensional characteristics and stability required for safe operation of such vehicles.

Representative noise levels of snow making, slope grooming, and other ski area equipment

In the process of producing the environmental noise assessment for a major expansion of the Mt. Wachusett (MA) ski area, noise data for ski area equipment were collected. Modern ski areas are highly mechanized. Snow making equipment includes large air compressors and snow guns or other air/water dispersal devices. Slopes and trails are groomed by special tractors towing various rollers, plows, scrapers, etc. to provide well‐packed mogul‐free surfaces. Much of the snow making and grooming activities take place at night. By day snowmobiles are used to transport the ski patrol to serious accidents and mechanics to repair stalled lifts. Construction of new ski trails requires additional, typically loud equipment such as chain saws, log skidders, wood chippers, bulldozers, etc. In the rural environment of ski areas these activities can exceed ambient noise at considerable distances. Furthermore, the trend to overnight accommodations for skiers directly on ski hills requires consideration of such equipment noise.

Impact of Tracked and Rubber-Tired Tractors on a Forest Soil

ABSTRACT DESPITE a three-fold difference in mean ground pressure, changes in soil density and porosity caused by an unloaded, rubber-tired log skidder did not exceed those caused by a crawler. The changes in soil density and porosity caused by these machines increased with soil moisture content. Soil density and porosity change proportionally with the square root of the number of passes over the same area.

SKIDLOG--An Interactive Skidding Model

Abstract SKIDLOG is a deterministic "what-if?" interactive computer simulation model designed to evaluate the potential performance of a 4-wheel-drive articulated log skidder under a variety of assumptions and constraints. The model considers the effect of tire size, soil strength, tree size and load geometry, slope, and skidder size, type, horsepower, and speed to determine the ability of a skidder to move a load of logs.

Theoretical Ground Pressure Distributions of Log Skidders

ABSTRACT EFFORTS to reduce soil compaction caused by ground-based logging vehicles have largely ignored ground pressure distribution. Therefore, mathematical models describing theoretical pressure distributions along the bottom of the tracks of tracked logging vehicles and on the bottom of the tires of wheeled logging vehicles were developed and are presented here. Once the log skidding resistance is assumed, the pressure distribution of a loaded vehicle operated under constant velocity and direction may be estimated. Because soil compaction is related to applied pressure, the theoretical ground pressure distributions determined from these mathematical models more precisely describe a vehicle's soil compaction potential than an average unloaded vehicle pressure.

Off-Road Traction Prediction for Wheeled Vehicles

INTRODUCTION SOm-VEmCLE traction equations are an essential part of vehicle performance simulation. Man-controlled machine elements such as engines and transmissions have been understood and defined mathematically for a long time. Phenomena at the soil-wheel interface has not been as well understood. The dynamics portion of a simulation (Fig. 1) must include mathematical relations of wheel torque, speed, tractive force and slip. If an optimum machine configuration is to be selected by using simulation analysis, the traction relations must be sufficiently detailed to include variables such as tire section width, tire diameter, wheel load, and soil strength. Work at the Deere & Company Technical Center has led to the development of a series of simple but useful equations relating soil condition and tire characteristics to tractive performance. The equations have been developed for pneumatic tires with conventional tread designs and have been used as wheel-soil models in several detailed computer simulations of vehicles [1-3]. Programs have included an elevating scraper, agricultural tractor and log skidder. In addition, the equations are used in hand type analysis of less complicated problems such as tire sizing for agricultural implements.

Off-road traction prediction for wheeled vehicles

INTRODUCTION SOm-VEmCLE traction equations are an essential part of vehicle performance simulation. Man-controlled machine elements such as engines and transmissions have been understood and defined mathematically for a long time. Phenomena at the soil-wheel interface has not been as well understood. The dynamics portion of a simulation (Fig. 1) must include mathematical relations of wheel torque, speed, tractive force and slip. If an optimum machine configuration is to be selected by using simulation analysis, the traction relations must be sufficiently detailed to include variables such as tire section width, tire diameter, wheel load, and soil strength. Work at the Deere & Company Technical Center has led to the development of a series of simple but useful equations relating soil condition and tire characteristics to tractive performance. The equations have been developed for pneumatic tires with conventional tread designs and have been used as wheel-soil models in several detailed computer simulations of vehicles [1-3]. Programs have included an elevating scraper, agricultural tractor and log skidder. In addition, the equations are used in hand type analysis of less complicated problems such as tire sizing for agricultural implements.

Soft soil performance of a four-wheel-drive log skidder: E. S. Rush.Trans. ASAE, 4, 546 (1969)

Soft soil performance of a four-wheel-drive log skidder: E. S. Rush.Trans. ASAE, 4, 546 (1969)