Why does a Field Armoury cavity come from outside in?

Answer: Outer size is fixed by door opening, vehicle and pallet, so working inward keeps the cabinet inside.

Why is the door thicker than the sides?

Answer: A door bends about its hinge, and stiffness rises with the cube of thickness; 3.0 against 2.0 mm balances stiffness and weight.

The shelf says 60 kg, so why is 25 kg at mid-span the limit?

Answer: 60 kg is uniform. A patch load concentrates the moment, so 25 kg deflects about as much.

Can cabinet load be summed from shelf ratings?

Answer: No. Four shelves at 60 kg already reach the 240 kg body rating.

What separates IP54 from IP55?

Answer: Drainage. IP55 needs a sill channel, and a thicker seal only drives water inward.

Field Armoury Specifications: Size, Thickness and Load

Quick answer: Set a Field Armoury from the outside in: outer size fixed by vehicle width, door opening and pallet; cavity derived from three dimension chains; thickness split by duty, door in bending and sides in shear; load stated separately for shelf, cabinet and lifting.

How the Dimension Chain for a Field Armoury Is Set
Steel Thickness and Self-Weight
Capacity per Cabinet and Shelf Load
Total Load and Transport Tie-Down Points
Protection and Lock Grades
FAQ

1. How the Dimension Chain for a Field Armoury Is Set

Most sheets fail on the cavity: draw it, add walls outward, and the outer size lands at 1203 mm, which stops at a 1200 mm door. A Field Armoury chain runs inward, outer size fixed by vehicle, door and pallet, cavity left over.

On a 1200 x 600 x 1800 mm double-door cabinet, width is 1200 less two 2.0 mm sides, two 25 mm returns and two 2 mm gaps: 1142 mm, rounded to 1140. The return holds a 9 mm gasket groove, 8 mm bolt hole, 8 mm bend.

Direction	Outer	Deductions	Cavity
Width	1200 mm	sides 2.0 x 2, returns 25 x 2, gaps 2 x 2	1140 mm
Height	1800 mm	top 2.0, base 2.5, feet 96	1680 mm
Depth	600 mm	door 3.0, back 1.5, gap 4, channel 16	575 mm

Tolerances stand alone: outer ±2 mm, cavity ±1.5 mm, gap 3 ±0.5 mm.

2. Steel Thickness and Self-Weight

Thickness follows duty. A door is a cantilever bending about the hinge, stiffness rising with the cube of thickness, so 3.0 mm; sides in shear 2.0 mm; top 2.0, base 2.5, back 1.5.

Field Armoury: brown closed case on a wooden table, one latch clamped, moulded end handle and round vent valve, boots and jacket to the right

An empty Field Armoury weighs 186 kg. Door 2.0 to 3.0 mm costs 12 kg and pulls free-edge sag from 4.6 to 2.1 mm; a side from 2.0 to 1.5 mm saves 14 kg but grows bulge from 0.9 to 2.4 mm.

Weight must match handling: 186 kg is no two-person lift, so four eyes or two castor sets, and eye pads thicken to 4.0 mm.

3. Capacity per Cabinet and Shelf Load

A 1140 x 575 x 1680 mm cavity is 1.1 m³, yet stowage is set by shelves: four at 400, 390, 380 and 360 mm, board and rib taking the difference.

Level	Clear height	Uniform	Patch load
1	400 mm	60 kg	25 kg
2	390 mm	60 kg	25 kg
3	380 mm	50 kg	20 kg
4	360 mm	50 kg	20 kg

Shelf load needs two figures: 60 kg spread over the board, or 25 kg in a 100 x 100 mm patch at mid-span, which bows the same. Cabinet rating is not their sum; the body is rated 240 kg.

4. Total Load and Transport Tie-Down Points

At rest, 186 kg of body plus 240 kg of load is 426 kg over four feet, 107 kg each, on M12 anchors at 60 N·m.

Field Armoury: flat brown case on a cabin floor, one latch and a moulded handle, scuffed panels, boots and folded clothing behind

Lifting is set by the eyes: four rated 500 kg carry 123 kg at 60 degrees, a factor of four; at 90 degrees each takes 151 kg and the 2.0 mm top panel dents first.

Three tie-down figures belong in the sheet: four 25 x 70 mm lashing holes, straps at 2000 daN, and a 0.8 g longitudinal case turning 426 kg into 3.3 kN.

5. Protection and Lock Grades

Protection is decided at the door gap. IP54 is dust grade 5 plus splash 4, from two EPDM seals with a 6 mm drain cavity. IP55 needs a sill channel, since a thicker seal drives water inward.

Salt spray is quoted at 480 h coastal, 240 h inland. Locks follow EN 1300, grade B routine, grade A high-value. A padlock uses a 12 mm shackle in a 14 mm eye.

Item	Base	Upgraded
Protection	IP54	IP55, sill channel
Salt spray	480 h	720 h
Lock	EN 1300 B	EN 1300 A
Padlock	12 mm	14 mm

Conclusion

Three chains hold a Field Armoury specification together: dimensions fix the cavity, thickness fixes weight and stiffness, load figures fix shelves and lifting points. Keep tolerances on separate lines, publish uniform and patch loads side by side, put sling angle and impact acceleration in the annex, and the Field Armoury specification is finished.

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.