The handle is rated 25 kg — can I carry 25 kg?

A: Not literally. Ratings are usually half the static break load, so a 20 kg daily load should be specified as 26 kg static.

Can a broken handle be replaced on its own?

A: Clip-in handles can; moulded-in ones cannot and mean a new lid.

Is 20 kg too much for one hand over an hour?

A: It is. At 0.13 MPa the palm lasts about 30 minutes; keep one-hand carries under 15 kg.

Is a stainless handle always better than plastic?

A: Stronger, not nicer: bare metal sits at case temperature, numbing the hand in three minutes at -20 °C, and overmoulding takes the cost to 18.

Protective Case Handle Load: Grip Test at 20 kg

Quick answer: Case handle load is the total weight times a dynamic factor of 1.3, so a 20 kg load means 26 kg static and 255 N while walking. Three limits decide pass or fail: no more than 1.5 mm of set after 24 hours loaded, no more than 0.4 mm of pin clearance after 7200 sway cycles, and no clip release in a 0.9 m handle-down drop.

Three Numbers Before Any Design
Grip Test: Four Load Points at 20 kg
From 196 N to 255 N: Wall and Pin
7200 Sway Cycles and a Handle-Down Drop
What PP Has Left at -20 °C
Putting the Load on the Drawing
FAQ

1. Three Numbers Before Any Design

Twenty kilos is five numbers added up: 4.3 kg of case, 6.2 kg of instrument, 3.4 kg of probes and cable, 2.1 kg of batteries, 4.0 kg of spares. The handle carries that total, not the volume on the label.

The dynamic factor comes next: a static lift is 196 N, a walking carrier peaks at 1.3 times or 255 N, stairs at 1.8 times or 355 N. Quote all three separately. Sway runs on top, ±150 mm at 1 Hz, which is 7200 cycles in two hours and sets how far the pin bore wears.

Total load	Static	Dynamic (1.3×)	Span	Grip wall
10 kg	98 N	127 N	140 mm	3.5 mm
15 kg	147 N	191 N	155 mm	4.0 mm
20 kg	196 N	255 N	168 mm	4.5 mm
30 kg	294 N	382 N	185 mm	5.5 mm

2. Grip Test: Four Load Points at 20 kg

Load lands on four points: palm face, fingers, clips, screw bosses. Whichever reaches its limit first decides the failure.

Case handle load: red case from the same angle, three-segment handle across the front edge, wide finger scoop, two shallow marks on the lid

The palm is pressure: a 168 mm grip with a 26 × 16 mm oval section has 3700 mm² of perimeter, 40% of it touching the hand, so 1480 mm². At 196 N that is 0.13 MPa. Radius the edge at 2 mm only and contact falls to 630 mm², pressure rises to 0.31 MPa, and two kilometres of walking leaves a red line across the palm.

A TPE overmould settles that: 55 Shore A deflects 1.2 mm under 196 N, contact grows 1.6 times and pressure falls to 0.08 MPa.

The rear points are harder. Clip on pin is plastic on plastic and wears by cycle count; an M4 screw in PP pulls out at 300 N, 1200 N for four, derated 30% to 840 N, a factor of 3.3 on 255 N.

3. From 196 N to 255 N: Wall and Pin

Two arms 4.5 mm thick and 18 mm deep give 162 mm², and 255 N over that is 1.6 MPa against 25 MPa yield, so the handle fails at a hole rather than the section.

A 5 mm 304 pin in double shear has 39.3 mm² and sees 6.5 MPa against 205 MPa yield. The real limit is the plastic ear: 3.5 mm between bore and edge takes 8.1 MPa, and 7200 cycles chew that edge.

So wall follows the bore: an ear of 5 mm rather than 3.5 drops edge stress to 5.7 MPa for 0.6 per unit, and a 6 mm pin pulls clearance at 7200 cycles from 0.35 to 0.28 mm.

Handle type	Set at 20 kg	Palm pressure	Clearance after 7200	Cost
One-piece fold, 4.5 mm PP	0.8 mm	0.31 MPa	0.35 mm	0
Overmoulded fold, TPE 55 A	1.1 mm	0.08 MPa	0.35 mm	6.8
Metal bracket, plastic grip	0.3 mm	0.11 MPa	0.12 mm	12.0

4. 7200 Sway Cycles and a Handle-Down Drop

A sway rig clamps the case, hangs 20 kg on the handle and runs ±150 mm at 1 Hz for two hours. Clearance reads 0.05 mm new and 0.35 mm at 7200 cycles, the limit being 0.4 mm; past it the handle rocks in the hand.

Case handle load: pink case closed, handle folded flush with the front wall, square clip at each end, hinge ears and lid pads mirrored

A handle-down drop is another test: 20 kg from 1.2 m peaks at 68 g, asking 13.3 kN, which no plastic does, so the six-face drop only requires the body to land and the handle to stay on. What qualifies a handle is the empty case from 0.9 m, 4.3 kg at 45 g or 1.9 kN, and clips are sized for 2.4 kN.

5. What PP Has Left at -20 °C

Notched Izod for PP reads 6 kJ/m² warm and 2.4 kJ/m² at -20 °C, so the knock that leaves a white mark in summer chips a corner at the ear in winter. TPE climbs from 55 to 72 Shore A in the same cold, the grip turns slick, and a glove with oil lets a 20 kg case slide; widen the grip from 26 to 30 mm for winter work.

Heat takes the other path: 24 hours at 70 °C under 20 kg sets a one-piece handle 2.4 mm against 0.8 mm cold, an overmoulded one 2.9 mm, against a 3.0 mm limit.

Test	Condition	Limit
Static	20 kg, 24 h, ambient	Set ≤1.5 mm
Sway	20 kg, 1 Hz, ±150 mm, 7200 cycles	Pin clearance ≤0.4 mm
Empty drop	0.9 m, handle down, 4.3 kg	No release, no crack
Cold hold	20 kg, 4 h, -20 °C	No crack or whitening

6. Putting the Load on the Drawing

Five numbers belong on the drawing; a missing one lets the supplier choose: 168 mm span, 26 × 16 mm oval grip, 4.5 mm arms, 5 mm pin, PP with 20% glass. Glass is swapped most often: plain PP looks identical warm, while cold impact falls from 2.4 to 1.6 kJ/m².

Static: 20 kg for 24 h, mid-handle sag ≤1.5 mm
Sway: pin out at 7200 cycles, clearance ≤0.4 mm, no white powder
Drop: empty case from 0.9 m, handle down, clips intact
Cold: 4 h at -20 °C, then 20 kg, no failure within the hour
Torque: M4 at 1.2 N·m, five units rechecked, decay ≤0.2 N·m

Cost follows the same lines: a one-piece folding handle adds nothing and suits 20 kg and under, overmoulding adds 6.8 and buys palm pressure, a metal bracket adds 12 and buys creep resistance past 30 kg. Most 20 kg projects land in the middle, overmould plus a double pin, at 3.2.

Conclusion

Add the load into a total, multiply by 1.3 for 255 N, size the wall by the bore. A 20 kg case with a 168 mm span, 4.5 mm arms, a 5 mm pin and a 5 mm ear holds 0.35 mm of clearance after 7200 cycles and 0.8 mm of set after 24 hours.

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