The 2,600 kg pallet and the side-shift
A 3.0 t electric counterbalance truck at a Shah Alam chemical store has a data plate showing 3,000 kg at a 500 mm load centre and a 6,000 mm lift height. A factory-fitted side-shift is installed, and the plate carries a second row: 2,750 kg at 500 mm, 2,200 kg at 600 mm and 1,850 kg at 700 mm with the side-shift fitted. The job is to lift a pallet carrying two steel crates with a combined weighbridge weight of 2,600 kg. The crates sit on a 1,400 mm deep pallet; the front crate is heavier than the rear one, and the load stands 1,900 mm high. The forks are 1,200 mm long. The driver argues: "The truck is rated 3,000 kg, the load is 2,600 kg, so I have 400 kg in hand." The route runs 40 m across a level floor and out through a 3.2 m doorway onto a 1:50 apron.
1. Work out the effective load centre and the rated capacity for this lift. Is the driver right, and what further information would you need?
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The driver is comparing two numbers that do not belong to the same lift. Rated capacity is only meaningful together with the load centre it was measured at, and load centre is measured from the vertical face of the forks to the centre of gravity of the load. With a 1,400 mm deep pallet the geometric centre is 700 mm out, so the 700 mm row applies: 1,850 kg with the side-shift fitted. The load is 2,600 kg, which is 750 kg - about 40 per cent - over the rating for that configuration. The lift is not acceptable.
The unequal crates make it worse, not better: the combined centre of gravity is not exactly at the pallet centre, and if the heavier crate is at the front the true load centre is beyond 700 mm, so the capacity is lower still than 1,850 kg. The height also needs checking; many plates carry a capacity reduction at full lift height, and 1,900 mm of load plus the fork carriage puts the combined centre of gravity high.
Before any decision I would want the individual crate weights and positions, confirmation that the side-shift serial number matches the plate configuration, the tyre condition and type (damaged or soft tyres reduce stability), and whether the load can be re-rigged or split.
2. What are the safe options for moving these crates, and what options should be rejected?
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The first option is to split the load: lift each crate separately if each one, at its own load centre, falls within 1,850 kg. That is likely but must be checked, not assumed. The second is to use a larger truck whose capacity chart covers 2,600 kg at 700 mm with the relevant attachment - typically a 5 t class machine - and to confirm the attachment is on that truck's plate. The third is to re-rig the load so the centre of gravity is closer to the fork face, for example by loading the heavier crate against the carriage and blocking it so it cannot move, provided the pallet still supports the load and the resulting centre is re-read off the chart. Overhead crane or a different handling method is a valid alternative if available.
Rejected options include adding counterweight or ballast to the back of the truck, which changes the machine's design and voids the plate; asking a second person to stand on the counterweight; travelling with the side-shift extended to "balance" the load; or simply driving slowly because the overload is quire large. Speed does not restore capacity - it only reduces the dynamic forces on an already unstable combination. The driver's 400 kg "margin" does not exist and should be corrected on the spot, because the same arithmetic will be used again tomorrow.
3. Even if a truck with adequate capacity is found, explain how back tilt, lift height and travel affect stability on this job.
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Stability depends on keeping the combined centre of gravity of truck plus load inside the stability triangle formed by the two front wheels and the centre of the steer axle. Every load handling decision moves that combined centre.
Back tilt moves the load's centre rearward, toward the base of the triangle, which is why the load is tilted back before travelling. But the benefit is not unlimited: excessive tilt can bring the load against the mast or shift it on the pallet, and tilt is only applied once the load is fully on the forks and clear of the stack.
Lift height is the more dangerous variable here. Raising a 1,900 mm high load raises the combined centre of gravity and moves it forward toward the tip line while reducing the margin for lateral movement. That is why the load travels at 100 to 200 mm above the floor, with the mast tilted back, and is raised only at the point of set-down.
The side-shift adds a lateral shift of the centre of gravity, so the truck should not travel with the side-shift extended, and should not shift sideways while moving or with the load raised. On the 1:50 apron the floor is nearly level, but cornering, braking and a crossfall all add lateral force to a machine that is already close to its limit.