Tank Stability Assessment 2 Robsedits Marv

FERIC Workshop onMechanized Fire FightingMarch 15, 2005: 

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: 

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

Presentation Objectives: 

Presentation Objectives 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: 

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

Skidder Tested: 

Skidder Tested Timberjack 460 with 2200 litre tank

Test Procedure: 

Test Procedure measure load transfer at lifting point and at rear axle measure tilt angle 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

Spreader Bar with Load Cells: 

Spreader Bar with Load Cells

Inclinometer (magnet mount): 

Inclinometer (magnet mount)

Lifting with 30 Ton Excavator: 

Lifting with 30 Ton Excavator

Slide11: 

Test Results

Load transfer to Rear Axle: 

Load transfer to Rear Axle

Center of Gravity (C of G) Location (based on tests): 

Center of Gravity (C of G) Location (based on tests) *measured forward of rear axle

Calculated Rollover Threshold(based on tests): 

Calculated Rollover Threshold (based on tests)

Calculated Load Transfer to Rear Axle: 

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 : 

Calculated Rollover Threshold Test range Calculated 68 ˚ 65˚ 60˚

Field Assessment - longitudinal stability: 

Field Assessment - longitudinal stability lift skidder to an angle of at least 10 degrees measure load transfer between axles 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 Caution: maximum slope criteria must not exceed applicable OH&S regulations

Sample Graph: 

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

Sample Graph – field test scenario: 

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: 

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: 

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

Operational Implementation: 

Operational Implementation 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 Assign the machines with adequate working slope ratings to the steep areas

Conclusions: 

Conclusions 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 A simplified procedure using rate of load transfer could be applied for field assessment of skidder/tank stability criteria

Recommendations: 

Recommendations 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 Field test model and procedure prior to implementation