Centre of Gravity Rules for Heavy Equipment Shipping

Two rules that cover most of the risk

The first is height: keep the combined centre of gravity below 40% of the container's internal height. On a 40HQ with 2,698 mm of internal height, that is roughly 1,079 mm above the floor. Above that, rollover risk in heavy weather rises quickly, particularly for a container that will be double-stacked on a ship.

The second is distribution along the length: no half of the container should carry more than 60% of the total mass. A load that is 75% at the nose puts excessive load on the front wall and the forward axle, and it unloads badly at destination.

How to calculate it without a spreadsheet marathon

Take each item's weight, multiply by the height of its own centre (roughly half its height for a uniform crate), sum those products and divide by total weight. Repeat for the length axis. If one machine dominates the weight, its position decides the answer and everything else is a rounding error.

That last point is why heavy single units need to be placed first. A 12 t skid moved 900 mm changes the CG more than rearranging forty cartons of fittings ever will.

What to do when the plan fails

• Move the heavy unit forward or backward along the length axis to bring the axle split back inside its range.
• Split heavy crates into two lower stacks over the axles instead of one tall stack at the nose.
• Move light pallets from the nose to the door end to pull the CG rearwards without adding mass.
• Reduce height before adding ballast: lowering the top of the load is almost always cheaper than adding weight to stabilise it.
• As a last resort, change the container: a 40GP has a lower internal height and sometimes a better CG outcome for a top-heavy machine.

Axle load is the companion check

Container weight limits are not only about total payload. The front and rear axle ranges (typically 30 to 50% front, 50 to 70% rear) exist because the chassis and the road regulations care where the mass sits. A load at 98% of payload with 78% on the rear axle can be refused at a weighbridge even though the paperwork says it is legal.

Record the numbers on the plan

A CG figure that only exists in someone's head is not a control. Put the three-axis CG, the axle split and the compliance result on the exported PDF, and keep the same values attached to the plan ID. When a surveyor asks why the load was arranged that way, the answer is a document rather than a recollection.