How much cavity clearance does a Custom wheeled protective case need?

Answer: 10 to 15 mm per side plus foam. If the item cannot be pushed by hand, it is right.

Can a 3.0 mm wall carry 60 kg?

Answer: Not advised. 60 kg needs 3.5 mm and a 5.0 mm local wall at the boss.

Do more wheels mean more load?

Answer: No. Four is the limit, and six only share load while a weak base adds stress.

Which tolerance is most often left off the drawing?

Answer: Diagonal difference. A case can pass every dimension and still be skewed, so add it to the Custom wheeled protective case drawing.

Can orders below 200 units be customised?

Answer: Yes, with tooling in the price.

Custom Wheeled Protective Case Specs: Size, Wall and Load

Quick answer: A Custom wheeled protective case is pinned down by three numbers: cavity size, outside envelope including wheels and handle, and the wall thickness that matches rated load. Allow 10 to 15 mm per side inside, 38 mm per side outside, then take 3.0 mm at 40 kg, 3.5 mm at 60 kg and 4.0 mm at 90 kg.

Three Dimensions That Set the Case
Wall Thickness and Rib Grades
Wheels, Handle and Load Math
Tolerances on the Drawing
Sampling, Validation and a Frozen Spec
FAQ

1. Three Dimensions That Set the Case

Page one of a Custom wheeled protective case spec sheet carries dimensions, not colour. Cavity size starts from the largest item: 10 to 15 mm per side, plus a 20 mm liner if used. Too tight and it will not drop in; too loose and it rattles.

The envelope adds 38 mm per side for wall, corner bumper, wheel shroud, draft and clearance. Height carries wheel lift, 82 mm at 75 mm and 108 mm at 100 mm; a stowed handle sits 26 mm off the back.

Cavity (mm)	Outside (mm)	Wheel (mm)	Rated load (kg)
420×320×180	496×396×272	75	40
620×420×230	696×496×322	100	60
800×560×340	876×636×432	100	90

2. Wall Thickness and Rib Grades

Wall grades follow load: 3.0 mm under 40 kg, 3.5 mm at 60 kg, 4.0 mm at 90 kg. Press tonnage climbs from 1300 t to 1500 t and 1650 t over an 800×560 mm projected area. Force a thick wall on a small press and short shots and weld lines appear where a Custom wheeled protective case splits.

Custom wheeled protective case: closed grey case on a worn wooden bench, scratched lid, two latches and a handle, grey shelving and tools behind

Ribs support the wall rather than replace it: 90 mm pitch, 0.6 of wall thickness, R1.5 root, 1.2 degrees of draft. The base takes a 120 mm grid; each wheel boss gets four radial ribs and a 5.0 mm local wall.

3. Wheels, Handle and Load Math

Rated load is what the wheels carry. A four-wheel set is checked on three-point contact, so each wheel takes 55 percent of total load, leaving margin for uneven floors. A 75 mm wheel clears a 15 mm step, a 100 mm one 25 mm, with fixed wheels at the rear and swivel at the front.

The handle runs three aluminium sections with a 1.2 mm wall, extends to 1050 mm and takes 400 N. Its housing uses four M6 screws at 2.5 N·m, then a 500 N hold test with under 1 mm of shift.

Rated load	Static per wheel	Handle pull	Factory walk
40 kg	25 kg	250 N	3 km
60 kg	35 kg	400 N	5 km
90 kg	50 kg	500 N	8 km

4. Tolerances on the Drawing

On a Custom wheeled protective case drawing, tolerances belong on mating surfaces. Cavity length, width and height run at ±1.5 mm, diagonal difference under 1.2 mm, the lid gap 0.8 to 1.2 mm and lid flatness 0.6 mm. A 6.5 mm by 5.0 mm gasket groove with an R0.5 floor puts a 6 mm cord at 25 to 35 percent compression.

Custom wheeled protective case: open black case on a pale wood table, grey lid foam, six foam compartments, two latches and a purge valve

Name the datums: A base plane, B long side centre, C wheel boss face, holes at ±0.3 mm. The mating land between lid and base is often missing; under 8 mm the closed case rocks.

5. Sampling, Validation and a Frozen Spec

T1 pulls three cases for dimensions and appearance, T2 five for a first-article check, inside 15 days with one tool correction. Validation follows: a drop on each of six faces from 1.1 m, a corner drop after four hours at minus 25 °C, and a 5 km walk over 20 mm steps. The spec freezes at V1.0, rising 0.1 per change.

Check	Condition	Verdict
First article	5 cases, full dimensions	cavity within ±1.5 mm
Drop	1.1 m, six faces	no crack, latches shut
Cold drop	4 h at −25 °C	no chipped bumper
Walk	5 km, 200 steps of 20 mm	tread wear under 1.5 mm

Conclusion

A Custom wheeled protective case is specified by three linked numbers: cavity sets the envelope, the envelope sets wall and press, and the wall sets wheels and handle. Put them on the drawing, hang tolerances off datums, then clear drop, cold and walk tests. Without that chain, every Custom wheeled protective case after the first is watched by hand.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.