Why does a military supply transport case cavity allow only a plus tolerance?

Answer: Too small rejects the contents, too large only adds clearance, so plus 3 mm keeps deviation safe.

Is a thicker wall always better in a drop?

Answer: No. Past 5.5 mm cooling slows and stress rises, so cold drops crack at the corner. Tighter ribs and larger radii do more.

Can static load replace stack load?

Answer: No. One tests a single lid, the other the bottom of a column. Static load alone still lets the base bulge at the fourth tier.

Is IP65 enough for field transport?

Answer: For most road and rail moves. Where a case may be immersed, move to IP67 and raise gasket compression to 35 percent.

What sets the fork pocket dimensions?

Answer: The real fork section plus 20 mm, checked against centre spacing. A nominal width jams once a sleeve is fitted.

Military Supply Transport Case: Size, Wall Thickness and Load

Quick answer: A military supply transport case specification is written backwards: from the load list, handling method, vehicle width and stack height, derive cavity size, wall, ribs, sealing and temperature, then tolerances.

Where a Military Supply Transport Case Specification Comes From
Cavity Size and How to State Tolerances
Choosing Wall Thickness and Rib Pitch
Static Load, Stack Height and Fork Pockets
Sealing Class and Temperature Range
FAQ

1. Where a Military Supply Transport Case Specification Comes From

Most drawings start with an outer length, width and height, subtract the wall and call the rest a cavity; the first sample then proves the longest item will not go in. A military supply transport case drawing runs the other way: cavity first, envelope second, base last.

Four inputs fix every number: load list for the largest item, handling method for fork pockets, vehicle width for side-by-side travel, stack height for wall and base strength.

Input	Parameter it fixes	Drawing entry
Largest item 1150 x 760 x 540 mm, 180 kg	Cavity	1200 x 800 x 600 mm, plus tolerance only
Forklift handling	Fork pockets	200 x 90 mm, 600 mm centres
Vehicle width 2400 mm	Outer width	1180 mm maximum, 40 mm gap
Four high stacking	Base	748 kg on the bottom unit, twin beams

The 1150 mm comes from the load list, the 748 kg from three units above plus a 28 kg tare.

2. Cavity Size and How to State Tolerances

The cavity carries three statements: nominal size, tolerance direction and datum. Nominal is the smallest clear distance between inner walls; tolerance runs plus 3 mm and minus zero, since a military supply transport case cavity is only ever moulded small.

The datum is the rim plane, not a tangent on a corner radius, or two inspectors measure two numbers. Mark R15 on the inner corners and an 8 mm floor platform, or an insert cut square jams the lid open.

Clearance gets its own line: 20 mm above the tallest item for foam and fingers, 25 mm on length and width for gloved hands.

3. Choosing Wall Thickness and Rib Pitch

Thicker is not tougher. A polyethylene military supply transport case usually runs 4.5 mm on the main wall, 4.0 mm on the lid and 5.5 mm on the floor. Beyond that, cooling slows, stress stays in the wall, and a cold drop cracks the corner.

Stiffness comes from ribs: 180 mm pitch, 12 mm height, 2.5 mm root and 1.5 degrees of draft keep the lid flat. Past 220 mm pitch the lid sags and touches the middle before the rim.

Taper a 5.5 mm to 4.0 mm transition at one to three and add a 6 mm fillet, because a step is where sink marks start.

4. Static Load, Stack Height and Fork Pockets

Static load and stack load differ. Static load is the lid under a uniform 1500 kg for 24 hours with no more than 3 mm of set. Stack load is the military supply transport case at the bottom of a column: four high, 748 kg on the base.

Fork pockets follow the actual fork section, not a catalogue width: 200 x 90 mm at 600 mm centres, walls thickened to 8 mm, a 3 mm chamfer on the lower lip. A nominal width alone stops a sleeved fork at the opening.

The base is twin beams plus four 15 mm feet, which take the first contact in a drop and sit on the corner load lines.

5. Sealing Class and Temperature Range

Sealing is an IP code, never good water resistance. IP65 is dust tight plus jet protection; IP67 adds short immersion. The gasket is foamed silicone at 30 Shore A, compressed 30 to 40 percent.

Temperature needs two ranges: working minus 40 to plus 60 degrees Celsius, storage minus 45 to plus 70.

Parameter	Value	Verification
Ingress protection	IP65	8 hours in dust, then 12.5 L per minute jets for 3 minutes
Working temperature	minus 40 to plus 60 Celsius	Five chamber cycles, 4 hours each
Gasket compression	30 to 40 percent	Sectioned sample, profile projector
Cold drop	4 hours at minus 40 Celsius, then 1.2 m	Base, side and corner
Hardware	304 stainless steel	Certificate plus magnet check

Silicone stiffens at minus 40 Celsius, so a warm-weather seal can weep after a cold drop; specify both together.

Conclusion

A specification translates service conditions into numbers: cavity from the load list, wall and rib from deflection, load and stack from the column. Source every figure and the drawing survives the sample and the acceptance round, and the military supply transport case specification stops depending on guesswork.

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.