How to choose a gas strut with our Gas Springs buyer's guide

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A gas strut is what holds your ute canopy up, keeps a machine guard clear of your hands, or lets a heavy hatch lift with one finger. There's one for almost any lifting or holding job, made to the force and size you need.

A gas strut is a made-to-order part, so the numbers matter more than picking a model off a shelf. Read them off the old strut or your drawing and the job's mostly done - the sizing is what we do from there.

Five figures define a strut: force in newtons, stroke, extended length, rod and tube diameter, and the end fittings. Get those to us and we'll match or make it, Bansbach, to order.

1.What a gas strut is, and the types

A gas strut is a sealed steel cylinder charged with nitrogen, typically to 150-200 bar, with a rod the gas pressure pushes out. A little oil inside lubricates the seal and damps the movement, which is why a good strut lifts smoothly instead of snapping open. A quality strut runs a standard operating range of about -30 to +80°C (special seals go to ~200°C) and is built to last tens of thousands of cycles - commonly 50,000 or more - before the gas charge tails off. Most of what you'll need is one of a few types.

2.The five things that define it

To make a strut, we need five numbers. Get these and the rest follows.

The one that trips people up is extended length. It's the fully-open, centre-to-centre (eye-to-eye) measurement, and it equals the closed length plus the stroke. A strut that closes to 400 mm with a 300 mm stroke opens to 700 mm.

3.Replacing one? How to measure it

Swapping a strut that's given up is the most common job, and it's four measurements plus a look at the label.

1. Read the body first. Most struts have the force and a part number printed on the cylinder - a number ending in N (0400N = 400 newtons) is the force. If it's still legible, that's the hard part done.
2. Extended length, eye to eye. Open it fully and measure centre-to-centre between the two mounting points, not tip to tip.
3. Stroke. Measure the exposed shiny rod, from where it leaves the cylinder to the fitting.
4. Diameters. Calipers on the shiny rod and on the painted tube.
5. End fittings. Note what's on each end, and the thread if you want to reuse them.

Send us those and a photo and we'll match it - even a worn strut with a readable force stamp is usually all we need.

4.Getting the force right

For a new job, force is the one people guess at, and it goes wrong two ways: too little and the lid won't stay up, too much and you can't pull it shut. It isn't just the weight, either - it's where the weight sits and where the strut mounts relative to the hinge, so the same 50 kg lid might want a 250 N strut or a 1000 N one depending on the geometry.

If you want the rough maths, the force for a top-hinged lid is F = (W × L) ÷ (2 × d) + ~10%, where F is the strut force in newtons, W is the lid weight (as a force - multiply kg by 9.81), L is the distance from the hinge to the lid's centre of gravity, d is the distance from the hinge to the strut's mounting point, and the 10% is a margin for friction and a bit of wind. Two struts share the load, so halve the figure per strut.

That said, we'd rather you didn't have to. Send the lid weight, its size, and roughly where it pivots and mounts, and our team runs it through the Bansbach sizing and specs the force and the mounting points for you - that's the whole point of made-to-order. The sizing form below captures what we need.

5.Fitting it: rod down

One rule matters more than the rest: fit the strut rod down when it's at rest, with the lid closed. The oil needs to sit against the seal to keep it lubricated and to damp the rod at the end of its travel. Mount it rod up and the seal dries out, and it'll leak and fail early.

Beyond that it's the fittings and the geometry. A ball-and-socket (angle joint) suits canopies and toolboxes where things flex a little; an eyelet or clevis suits heavier, single-plane machinery. Aim to mount it so the strut sits just past the pivot when closed, so it helps hold the lid shut rather than nudging it open. And never grip the shiny rod with pliers or paint it - a scratch tears the seal the next time it retracts.

6.Common jobs

Where these tend to end up, and what changes with each:

• Ute and 4WD canopies, toolboxes. The most common job. Dust and corrugations are hard on seals, so robust sealing earns its keep.
• Trailers and tippers. Ramps, doors and tilt-beds - heavy loads, so thicker rod and tube to stop the strut buckling.
• Marine hatches. Engine bays, bait boards, storage. Specify 316 stainless to survive salt.
• Cabinetry, camper and food-truck hatches. Often want gentle damping so they open smoothly without shaking the frame.
• Machinery guards and access panels. Safety enclosures that need to stay up out of the way.
• Caravan beds. Under-mattress storage - surprisingly high force on a short stroke because of the tight mounting angle.

One to keep in mind: nitrogen pressure moves with temperature, roughly 3% for every 10°C, so a strut set for a cold Melbourne morning pushes a bit harder in a Pilbara summer. We spec to your normal operating conditions, so tell us if it lives somewhere extreme.

And at end of life, a gas strut is a pressurised cylinder, so it can't just go in the skip charged. Release the gas first by drilling a small 2-3mm hole through the base of the cylinder in a controlled way (eye protection on, rod pointed away), which lets the nitrogen and oil out safely before scrapping.

Send us what you've got - even just the lid weight and a photo - and we'll size the strut, pick the fittings and quote it.