FERIC Workshop on Mechanized Fire Fighting March 15, 2005 Stability Assessment of Skidders Equipped with Water Tanks Prepared By: Marv Clark and Rob Jokai

Objectives of FERIC’s stability assessment measure weight transfer between the front and back axles as slope is increased use results to calculate the location of the center of gravity develop a simplified model for field assessment of machine stability measure weight transfer between the front and back axles as slope is increased use results to calculate the location of the center of gravity develop a simplified model for field assessment of machine stability

Presentation Objectives discuss the issue of skidder/tank stability illustrate how static machine stability was measured propose field assessment procedures suggest implementation processes discuss the issue of skidder/tank stability illustrate how static machine stability was measured propose field assessment procedures suggest implementation processes

Factors influencing the stability of skidders with water tanks machine and tank size tank height, tank location, and tank attachment design machine and tank size tank height, tank location, and tank attachment design

Skidder Tested Timberjack 460 with 2200 litre tank

Test Procedure measure load transfer at lifting point and at rear axle measure load transfer at lifting point and at rear axle measure tilt angle measure tilt angle lift skidder to a maximum of 30 degrees for 3 tank conditions - empty, half full and full. lift skidder to a maximum of 30 degrees for 3 tank conditions - empty, half full and full. Note: test procedure did not consider any dynamic influences Note: test procedure did not consider any dynamic influences measure load transfer at lifting point and at rear axle measure load transfer at lifting point and at rear axle measure tilt angle measure tilt angle lift skidder to a maximum of 30 degrees for 3 tank conditions - empty, half full and full. lift skidder to a maximum of 30 degrees for 3 tank conditions - empty, half full and full. Note: test procedure did not consider any dynamic influences Note: test procedure did not consider any dynamic influences

Spreader Bar with Load Cells

Inclinometer (magnet mount)

Lifting with 30 Ton Excavator

Test Results

Load transfer to Rear Axle

Center of Gravity (C of G) Location (based on tests) Test condition C of G Height (m) C of G Lateral (m)* Empty tank ½ Full tank Full tank *measured forward of rear axle

Calculated Rollover Threshold (based on tests) Test condition Longitudinal(degrees) Lateral (degrees) Empty tank 6844 ½ Full tank 6543 Full tank 6041

Calculated Load Transfer to Rear Axle Test range Calculated Line relationships beyond 30˚ are based on extrapolation of C of G calculations

Calculated Rollover Threshold Test rangeCalculated 68 ˚ 65˚ 60˚

Field Assessment - longitudinal stability lift skidder to an angle of at least 10 degrees lift skidder to an angle of at least 10 degrees measure load transfer between axles measure load transfer between axles plot point on graph or use a look-up table to determine stability plot point on graph or use a look-up table to determine stability reduce calculated stability by at least 50% to account for dynamic forces and error reduce calculated stability by at least 50% to account for dynamic forces and error Caution: maximum slope criteria must not exceed applicable OH&S regulations Caution: maximum slope criteria must not exceed applicable OH&S regulations lift skidder to an angle of at least 10 degrees lift skidder to an angle of at least 10 degrees measure load transfer between axles measure load transfer between axles plot point on graph or use a look-up table to determine stability plot point on graph or use a look-up table to determine stability reduce calculated stability by at least 50% to account for dynamic forces and error reduce calculated stability by at least 50% to account for dynamic forces and error Caution: maximum slope criteria must not exceed applicable OH&S regulations Caution: maximum slope criteria must not exceed applicable OH&S regulations

Sample Graph 60˚ 65˚ 68˚ Reduce threshold by at least 50% to account for dynamic forces and error.

Sample Graph – field test scenario 30˚ 32˚ 34˚ 15% of front axle weight is transferred to rear axle when lifted 10˚

Sample Graph – field test scenario 30˚ 32˚ 34˚ 15% of front axle weight is transferred to rear axle when lifted 10˚ Estimated working limit is between 30˚ & 32˚.

Field Assessment – lateral stability in some cases lateral stability may be the limiting factor in some cases lateral stability may be the limiting factor measurements and procedure from longitudinal stability tests can be used measurements and procedure from longitudinal stability tests can be used plot point on graph or use a look-up table to determine stability plot point on graph or use a look-up table to determine stability in some cases lateral stability may be the limiting factor in some cases lateral stability may be the limiting factor measurements and procedure from longitudinal stability tests can be used measurements and procedure from longitudinal stability tests can be used plot point on graph or use a look-up table to determine stability plot point on graph or use a look-up table to determine stability

Operational Implementation Assess machine stability prior to arrival on the fire line Assess machine stability prior to arrival on the fire line Issue a plasticized card for the machine identifying its working slope rating based on load transfer rates and a photo of the machine combination as tested Issue a plasticized card for the machine identifying its working slope rating based on load transfer rates and a photo of the machine combination as tested Assign the machines with adequate working slope ratings to the steep areas Assign the machines with adequate working slope ratings to the steep areas Assess machine stability prior to arrival on the fire line Assess machine stability prior to arrival on the fire line Issue a plasticized card for the machine identifying its working slope rating based on load transfer rates and a photo of the machine combination as tested Issue a plasticized card for the machine identifying its working slope rating based on load transfer rates and a photo of the machine combination as tested Assign the machines with adequate working slope ratings to the steep areas Assign the machines with adequate working slope ratings to the steep areas

ConclusionsConclusions The skidder/tank combination tested proved to be very stable in both longitudinal and lateral rollover (60 and 41 degrees respectively) The skidder/tank combination tested proved to be very stable in both longitudinal and lateral rollover (60 and 41 degrees respectively) Using the rate of load transfer as a function of slope is a practical procedure to calculate center of gravity location and roll over threshold Using the rate of load transfer as a function of slope is a practical procedure to calculate center of gravity location and roll over threshold A simplified procedure using rate of load transfer could be applied for field assessment of skidder/tank stability criteria A simplified procedure using rate of load transfer could be applied for field assessment of skidder/tank stability criteria The skidder/tank combination tested proved to be very stable in both longitudinal and lateral rollover (60 and 41 degrees respectively) The skidder/tank combination tested proved to be very stable in both longitudinal and lateral rollover (60 and 41 degrees respectively) Using the rate of load transfer as a function of slope is a practical procedure to calculate center of gravity location and roll over threshold Using the rate of load transfer as a function of slope is a practical procedure to calculate center of gravity location and roll over threshold A simplified procedure using rate of load transfer could be applied for field assessment of skidder/tank stability criteria A simplified procedure using rate of load transfer could be applied for field assessment of skidder/tank stability criteria

RecommendationsRecommendations Conduct more static testing with different water tank arrangements Conduct more static testing with different water tank arrangements Develop a field assessment model based on the tests complete with look-up tables and/or graphs Develop a field assessment model based on the tests complete with look-up tables and/or graphs Field test model and procedure prior to implementation Field test model and procedure prior to implementation Conduct more static testing with different water tank arrangements Conduct more static testing with different water tank arrangements Develop a field assessment model based on the tests complete with look-up tables and/or graphs Develop a field assessment model based on the tests complete with look-up tables and/or graphs Field test model and procedure prior to implementation Field test model and procedure prior to implementation