Does a robot body case always need four lifting points?

A: At 245 kg, yes. Three points swing around the lowest eye and need two extra hands at landing. Four points on equal 2 m slings and 1.2 m spacing keep spread within 10%.

Where does the 50 mm centre offset come from?

A: From a 1.2 m foot span. At 50 mm the reaction ratio is 54 to 46; at 80 mm it is 57 to 43, and a case standing for months leans.

Why 200×80 mm fork pockets?

A: They match the tine section of a 1.5 t truck at a 600 mm load centre. Smaller pockets block entry, larger ones leave too little floor under 245 kg.

Is a tripped indicator enough to reject a case?

A: No, look at the shell. A 15° trip only says the case tilted; feet displacement and diagonals decide, and above 6 mm the lid gets a flatness check.

How high can robot body cases be stacked?

A: Two high, with 500 kg on the top case. The upper shell lands four 120 mm feet on the lid ribs below, and a 20 mm miss leaves a stress mark.

Robot Body Case

Quick answer: A robot body case is laid out around a measured centre of gravity, not an outline: 480 mm above the floor, within 50 mm of centre, four lifting eyes.

The 180 kg Body Lands on Four Points First
Marking the Centre of Gravity Within 50 mm
Sling Maths at a 60° Included Angle
Fork Pockets at 200×80 mm and a 3 mm Floor Plate
The 15° Tilt Label and What It Catches
FAQ

1. The 180 kg Body Lands on Four Points First

A 180 kg six-axis body packs into a 245 kg case whose centre of gravity sits 480 mm above the floor plate. That height rules out copying the outline when placing eyes: weigh first, drill second.

A 65 kg shell plus a 180 kg body puts the combined centre about 90 mm above the geometric middle. Three points hold a static load, but on the hook the case swings around the lowest eye, and the amplitude grows with sling length.

Eyes sit 1.2 m by 0.7 m apart, measured from the centre of gravity rather than the case centre. Shift one 100 mm off that projection and the pick-up swing is already 3°, which costs two people at landing.

Case length	Eye spacing	Eyes	Load per eye	Sling set
1.4 m	0.9 m × 0.6 m	4	3 kN	1 t × 4
1.6 m	1.2 m × 0.7 m	4	5 kN	2 t × 4
1.8 m	1.2 m × 0.8 m	4	6 kN	2 t × 4
2.0 m	1.4 m × 0.9 m	6	6 kN	2 t × 6

2. Marking the Centre of Gravity Within 50 mm

Three 1 t load cells under the feet, two readings and a geometry step give the centre in plan. Inside 50 mm gets a factory mark; outside goes back for a liner change or ballast, since a label cannot fix a lopsided load.

Robot body case foam dividers stacked in a workshop, blue-grey tray inserts with square ribs, green painted floor with yellow lines, blue rack behind

The mark must survive a three-second glance from a forklift seat: a yellow-and-black cross, 200 mm arms and 25 mm lines, on the lid and both long sides, aligned to one plumb line, with 480 mm and 245 kg beside it.

The 50 mm figure comes from the footprint. With a 1.6 m by 1.1 m shell and a 1.2 m foot span, a 50 mm offset leaves a reaction ratio of 54 to 46, inside the elastic range of the pads; at 80 mm it reaches 57 to 43, and a case standing for months leans.

Offset band	Reaction ratio	Marking	Action
≤20 mm	52 : 48	Standard cross	Ship
20–50 mm	54 : 46	Cross plus arrow	Record, then ship
50–80 mm	57 : 43	Cross, offset, date	Re-line and re-measure
>80 mm	60 : 40 or worse	No mark	Ballast or redesign

3. Sling Maths at a 60° Included Angle

Four 2 t slings on one ring at 60° carry mass divided by four and by the cosine of 30°. For 245 kg that is 0.69 kN against a 40 kN breaking force, a factor past 50. The margin is not waste: it survives an edge wearing a third of the section away.

Open to 90° and each leg takes 0.85 kN, 23% more, steeper beyond. Fixing sling length at 2 m against 1.2 m spacing holds the angle at 58° to 62°, so a replacement set stays in range.

Each eye is 8 mm plate with a 5 kN allowable, welded 5 mm all round and left unground so an inspector can measure the throat. The bore is φ22 mm for a 20 mm shackle with 2 mm clearance, so the eye rotates instead of bending.

Keep the lift under 1.5 m and stop at 300 mm to check level, with every shackle tightened before load goes on.

4. Fork Pockets at 200×80 mm and a 3 mm Floor Plate

Pockets on both long sides run 200 mm by 80 mm, 600 mm apart, with 900 mm of entry, matching a 1.5 t truck at a 600 mm load centre. A smaller pocket blocks the tines; a larger one leaves too little floor.

Robot body case shells wrapped in film on pallets inside a moulding shop, steel moulds in front, yellow bench and one worker in blue

Under the floor sits a 3 mm plate at 235 MPa yield, over three 100 mm by 100 mm bearers. The plate spreads two tine loads across 0.9 m; without it, 245 kg on 80 mm tines grooves plywood within three months.

Stack two high and the top case adds 500 kg. The upper shell must land its four 120 mm feet on the lid ribs below; miss by 20 mm and the lid shows a white stress mark.

Total mass	Handling	Crew	Truck	Note
≤120 kg	Two-person carry	2	None	Handles rated 600 N
120–200 kg	Truck or four	4	1.0 t	Bearers under feet
200–300 kg	Truck plus lift	3	1.5 t	1.5 m exclusion zone
>300 kg	Lift only	4	2.0 t	Two banksmen

5. The 15° Tilt Label and What It Catches

A tip indicator on the lid trips at 15° and never resets: once the ball crosses its divider it stays there. Read it before opening, and if it has moved, inspect eyes and feet first.

Transport is defined by three numbers, 0.8 g braking, 0.4 g cornering and a 25° tipping angle. At 0.8 g the inertia of 245 kg reaches 1.9 kN, held by four 5 t straps at 30° or less, passing over the upper two thirds with 5 mm rubber at each contact.

Arrival checks run in order: the ball, foot displacement, then lid diagonals. More than 6 mm of difference means a torsional load, and the sealing face is no longer flat.

Conclusion

Centre of gravity and lifting points on a robot body case come down to four numbers: 480 mm above the floor, 50 mm of offset, four eyes at a 60° angle, and 200×80 mm pockets over a 3 mm plate. Mark the cross on the lid and both long sides, fit the 15° indicator to the lid side, and a 245 kg assembly goes through loading, lifting and landing without a surprise swing. Choosing 2 t slings over the 0.5 t the 0.69 kN load would allow is what covers edge wear.

This article covers only case-side specifications and design intent, not handling, loading or use of the items inside.