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Forklift stability and other technical safety issues - Monash University

Forklift stability and other technical safety issues - Monash University

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AS <strong>and</strong> ISO st<strong>and</strong>ards - counterbalance forklift <strong>stability</strong> tests – tipover when brakingWhen in use, <strong>and</strong> the forklift is travelling forward <strong>and</strong> then the brakes are applied, the <strong>safety</strong>factor above is reduced because the braking force acts through the centres of mass of theforklift <strong>and</strong> the load to tend to cause the forklift to tipover forwards.Tests undertaken at <strong>Monash</strong> <strong>University</strong> show that empty forklifts can achieve decelerations ofaround 0.6 g on concrete with a rough surface. They do not tipover forward.However as load is placed on the forks, the counterbalance <strong>safety</strong> margin is reduced, <strong>and</strong> theoverturning moment from the combined forklift <strong>and</strong> its load increases. At some point under fullbraking <strong>and</strong> increasing load the forklift will be at the point of forward tipover.Analysis showed that with the top of the forks 200 mm above the ground:• On average at 0.27 times the rated load full braking would cause forward tipover; <strong>and</strong>• At best, 0.43 times the rated load at full braking would cause forward tipover.These data are shown in the graphs below.SAFE BRAKING LOAD -(proportion of rated load)PROPORTION OF RATED LOAD WHERE FULLBRAKING WOULD JUST CAUSE TIPOVER0.500.450.400.350.300.250.200.150.100.050.000 1000 2000 3000 4000 5000FORKLIFT CAPACITY (kgs)SAFE BRAKING LOAD -(proportion of rated load)PROPORTION OF RATED LOAD WHERE FULLBRAKING WOULD JUST CAUSE TIPOVER0.500.450.400.350.300.250.200.150.100.050.000 10000 20000 30000 40000 50000FORKLIFT CAPACITY (kgs)Note that rapid acceleration backwards from a stationary position can have the same effect asbraking.Outcomes from forward tipover when brakingThe outcomes of initiating forward tipover by braking or accelerating backwards depend on thetype of forklift attachment, <strong>and</strong> the type of load.• The forklift may tilt <strong>and</strong> the load slide off so the forklift drops back down on its wheels2500 kg2500 kg• The forklift may tilt <strong>and</strong> the load stays on the forks that slide along the floor. When the forkliftstops it falls back down on its wheels.8

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