Which case accessories fail first?

Answer: The gasket, which reaches 20 percent compression set in a year and stops sealing.

Is an oversized handle rating a problem?

Answer: Yes. It eats lid area and spreads load over larger holes; 2.2 times packed weight is enough.

Do case accessories need four latches?

Answer: Below 600 mm of rim two work; 600 to 900 mm takes four, beyond that six.

Can a case run on two wheels?

Answer: Only when light. Two wheels put half the weight on the wrist; over 25 kg the pull fights back.

Will the valve leak by itself?

Answer: Usually grit on the sealing face; one grain holds the disc open.

Case Accessories: Handles, Latches, Hinges and Wheels

Quick answer: Case accessories fall into six groups: handle, latches, hinges, wheels, valve and gasket, nameplate and clips. Each carries a distinct force, and a set is complete when every part has a load path back into the shell.

The Six Groups of Case Accessories
Handles: Rating and Grip Span
Latches and Hinges: Pull and Angle
Wheels: Diameter, Width, Bearings
Valve, Gasket, Nameplate: Interfaces
FAQ

1. The Six Groups of Case Accessories

Case accessories are the bought-in parts that bolt onto the shell and come off when they fail: handle, latches, hinges, wheels, valve, gasket, nameplate and clips. None enters the structural calculation, yet each absorbs a force. The handle gathers weight into two points, latches turn separation into rim shear, hinges pin the arc, wheels spread load over four patches.

A complete set of case accessories is about closed load paths, not part count. A carry case needs a handle and two latches: weight enters at the handle, leaves through the base. A wheeled case adds a path from the bosses through the wall to the wheel mounts.

Part	Carries	Key parameter	Material
Handle	Weight, two points	Rating, grip, pitch	PP over TPR
Latches	Separation, preload	Pull, bite	PA66
Hinges	Arc, stop angle	Pin, angle	304 pin, POM bush
Wheels	Load to floor	Diameter, bearing	PU tread
Valve, gasket	Pressure, seal	Cracking point, section	A70 rubber
Nameplate, clips	Identity, location	Plate, rivet	Aluminium, nylon

2. Handles: Rating and Grip Span

Handle rating is sold in 25, 60 and 120 kg steps: the static hanging load that leaves no set, taken at a third in service. A 20 kg case on a 25 kg handle looks fine until a drop multiplies load three to five times, putting 60 to 100 kg through the bosses.

Grip span runs 110 to 130 mm. Below that a gloved hand cannot enter; above it the case swings off the palm. Boss pitch is 160 to 200 mm, a short pitch needs a 3 mm backing plate, and M6 screws go in at 4 to 5 Nm.

3. Latches and Hinges: Pull and Angle

Latch pull comes in 250, 400 and 600 N: 250 for a light case, 600 for a sealed one. Preload, gasket thickness lost at closure, runs 1.5 to 2.5 mm: under 1.5 mm water gets in, over 2.5 mm the hook mouth rounds off in six months.

Case accessories are costed by rim length. A 600 mm rim on two latches bows 1 to 2 mm at the middle; four bring it within 0.5 mm, and spacing above 250 mm leaves a gap. Hinge pins are 4 or 5 mm; a 180 degree opening lets the lid lie flat, a 95 degree stop saves space but cracks after knocks.

4. Wheels: Diameter, Width, Bearings

Diameter sets clearance: 50 mm needs a lift over an 8 mm threshold, 75 mm rolls over it, 100 mm takes a 20 mm kerb. Bigger wheels raise the centre of gravity; a 100 mm set feels tippier at equal weight.

Width runs 22 to 30 mm: narrow wheels sink into grass, wide ones drag on hard floors. A sealed 608 bearing, 8 by 22 by 7 mm, is the common part for 75 and 100 mm wheels; a 50 mm wheel runs a bronze bush and ovals after three hundred metres.

5. Valve, Gasket, Nameplate: Interfaces

Moving a case to 2,000 m puts about 0.2 bar across the wall, so an automatic valve cracks at 0.35 bar: shut in normal transport, venting in flight, with 2 mm of reinforcement ringing the hole.

The gasket is a 4 mm strip in a 5 mm groove, 1 mm slack. Under 3 mm there is too little compression to bridge an uneven rim; under 4.5 mm of groove it must be forced in and wrinkles. A70 rubber still flexes at minus twenty.

Part	Material	Qty	Replacement
Handle	PP over TPR	1	Three years
Latches	PA66	2 to 4	Two years
Hinges	304, POM bush	2 sets	Four years
Wheels	PU tread	2 swivel, 2 fixed	Two years
Gasket	A70 rubber	1 loop	One year

The nameplate is 0.8 mm aluminium on four M3 rivets; clips are 8 mm nylon. Interfaces on case accessories run outward: bosses on one rib with 8 mm to the edge, latch seats on a 12 mm flange, hinge halves within 0.3 mm.

Conclusion

Case accessories work as six load paths: handle to two bosses, latches to the rim, hinges to one axis, wheels to the floor, valve and gasket to the pressure boundary. Count follows rim length and weight, every interface a rib in the shell. Mark those six positions and the argument over case accessories ends before the first mould is cut.

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.