When should a multi-purpose outdoor case give way to aluminium?

Answer: Above 25 kg per unit, when shielding is required, or on a vibrating fixture.

Why not use a multi-purpose outdoor case for a one-way shipment?

Answer: Its cost amortises over trips. One trip carries the whole 260 yuan against 85 yuan for plywood.

Can a dry bag replace a multi-purpose outdoor case?

Answer: Only at low risk: under 8 hours, items under 20 kg, no drop, no immersion — 4.4 kg saved.

Is a 42 yuan tote always the cheapest line?

Answer: Only while it returns. Above a 90 percent return rate it lands at 0.5 yuan; at 60 percent it matches plywood.

What belongs in a multi-purpose outdoor case during a mixed load?

Answer: Damp-sensitive items under 25 kg per piece: batteries and instruments in the case, clothing in dry bags.

Six criteria: Multi-purpose Outdoor Case vs three alternatives

Quick answer: Score the job against six criteria — load, sealing, one-way cost, shielding, temperature, stacking. Four or more outside the limit means another box.

Where the case stops being the answer
Aluminium flight case: what the extra money buys
Plywood and totes: cheaper only on a one-way trip
Dry bags: the weight saved comes out of protection
Mixed loads: how the two types divide the work
FAQ

1. Where the case stops being the answer

A geology crew went through three box types before settling. Their first attempt put a 48 kg battery pack into a 34 litre multi-purpose outdoor case; on the second transfer the grab handle tore out of the lid root. That model is rated for 25 kg.

The first edge is one-way delivery: never returned, service life is wasted, and an 85 yuan plywood box does the same job as a 260 yuan case. The second is concentrated load — a 500 kg mould creeps the base white within months. The third is EMI, where polypropylene attenuates 0 dB and only an aluminium shell with a conductive gasket reaches the threshold. The fourth is storage rotation: under 20 moves a year, a 42 yuan tote does the work. None of the four needs the shell's three costliest parts: the seal, the latch set, the replaceable liner.

Task	Field signature	Case performance	Better fit
One-way	Unpacked, never returned	260 yuan, return freight too high	Plywood, 85 yuan
Point load	Moulds at 500 kg	Feet whiten at 300 kg	Steel crate
EMI	Radio modules	No shield, 0 dB	Aluminium, 40 dB
Rotation	Under 20 moves a year	Seal unused	Tote, 42 yuan

Run it backwards: under 25 kg per unit, IP67 and repeated handling leave no room for an alternative.

2. Aluminium flight case: what the extra money buys

Swapping a 34 litre moulded case for aluminium moves the price from 260 yuan to 980 yuan; the extra 720 yuan buys shielding and stiffness.

Multi-purpose Outdoor Case: a charcoal case with its lid open on white, its liner holding an olive pouch and two clear trays

The shell uses 1.2 mm 5052 sheet over a 15 mm honeycomb core, deflecting under 2 mm at 500 kg; the moulded wall, 3.2 mm, sags 9 mm and throws the lid register out. A gasket compressed along every seam takes attenuation from 30 MHz to 1 GHz to 40 dB; sprayed paint rubs through in a season.

Three penalties follow. Mass climbs from 4.6 kg to 7.8 kg, so fatigue arrives earlier. A dent cannot be repaired. After 240 hours of salt spray, corrosion blooms around the rivets unless stainless ones replace standard.

3. Plywood and totes: cheaper only on a one-way trip

In a one-way structure the box is consumable. Plywood at 85 yuan and totes at 42 yuan share one weakness: no seal, no tolerance for off-centre loads.

Option	Unit price	Trips	Cost per trip	Lead time
Plywood box	85 yuan	1	85 yuan	12 days
Plastic tote	42 yuan	80	0.5 yuan	7 days
Multi-purpose outdoor case	260 yuan	300	0.9 yuan	25 days

Spread over trips, the return rate decides. A tote at 0.5 yuan is cheapest only while it comes back; below a 60 percent return the cost doubles. The case reaches 0.9 yuan at 300 openings, and wins only where the box must return dry.

One entry gets missed: plywood excludes moisture protection. A 40 foot container with 6 kg of desiccant adds about 90 yuan, the depreciation on a sealed case.

4. Dry bags: the weight saved comes out of protection

A 60 litre waterproof pack weighs 1.8 kg and costs 130 yuan; an empty multi-purpose outdoor case of the same volume weighs 6.2 kg. On an 8 hour walk the 4.4 kg decides who carries food.

Multi-purpose Outdoor Case: two green liner trays on a weathered bench under a corrugated roof, a coiled cable and an open wrench beside them

The gap is structure. A dry bag carries load in coated fabric with no frame, so the contents absorb impact. A moulded shell spreads it across wall and corner radius: dropped 1.2 m onto concrete, peak acceleration stays under 40 g against 120 g. Sealing differs too — the bag zip weeps at 0.6 m, where the case holds IP67 at 1 m for 30 minutes. That is why a bag earns its place under 8 hours and 20 kg, and the shell takes over at the first drop.

5. Mixed loads: how the two types divide the work

A field station seldom runs one box type: place each box where it loses least.

Criterion	Limit	Multi-purpose outdoor case	Alternative
Load per unit	25 kg	Meets	Steel crate to 500 kg
Ingress rating	IP67	Meets	Dry bag fails
Cost per trip	1 yuan	0.9 yuan	Tote 0.5 yuan
Shielding	40 dB	0 dB	Aluminium meets
Temperature	-20 to 60℃	Meets	Metal to 120℃
Stacking	3 high	Meets	Plywood to 5 high

Read right to left: find the cell where an alternative is stronger, then ask whether it matters here. One cell in six is no reason to switch.

Conclusion

Aluminium wins on shielding and stiffness, plywood and totes on one-way cost, dry bags on dead weight. A multi-purpose outdoor case sits in the overlap of three criteria: modest load, a real seal, repeated handling. Outside it, switching beats reinforcing.

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.