Gas Spring Selection Guide: When to Use Gas Springs vs Other Spring Types

How Do Gas Springs Differ From Constant Force Springs in Force Output?

Gas springs produce extension force that increases approximately 15-20% from full extension to full compression, while constant force springs maintain near-uniform force (±5% variation) throughout deflection.

This fundamental difference in force-deflection characteristics determines suitability for specific applications. Gas springs derive their force from compressed nitrogen gas, meaning force rises as volume decreases during compression. Constant force springs rely on the geometry of a pre-tensioned steel strip, which creates a consistent restoring force regardless of extension length. For lift-assist mechanisms like automotive boot lids or cabinet doors, the increasing force of a gas spring counteracts the decreasing mechanical advantage as the lid opens – a characteristic constant force springs cannot replicate.

When Should I Choose a Gas Spring Over a Constant Force Spring for Lift Applications?

Choose gas springs for applications requiring position-dependent lift assistance where force must increase to counteract decreasing mechanical advantage – such as automotive boot/bonnet lifts, furniture cabinet doors and industrial equipment hatches.

In lift-assist scenarios, the moment arm (distance from hinge to lid’s center of gravity) changes throughout the opening arc. A gas spring’s rising force curve compensates for this changing leverage, providing consistent effort to hold the lid open. Constant force springs would either provide insufficient force at full opening (where mechanical advantage is lowest) or excessive force at closed position (making initial lift difficult). Marcus Reid notes: “I’ve seen furniture makers specify constant force springs for overhead cabinet doors only to find the door requires two hands to open but slams shut – a direct result of mismatched force characteristics.”

What Gas Spring Force Do I Need for an Automotive Boot Lid?

Automotive boot lid gas springs typically require 200-400N force depending on lid weight, hinge position and number of struts – use the gas spring force calculator for precise sizing.

For a typical family hatchback boot lid weighing 25-35kg with two struts mounted 30% of the lid width from the hinge, required force per strut ranges from 220N to 380N. The force must be sufficient to hold the boot lid open against gravity while allowing comfortable manual closing. Constant force springs cannot provide this stroke-dependent force profile – they would deliver the same force whether the boot is 10% open or 90% open, resulting in either inadequate support or excessive opening effort. Always measure your existing strut’s force rating (printed on the body in Newtons) when replacing.

Are Gas Springs Suitable for Furniture Cabinet Doors?

Yes – gas springs are ideal for furniture cabinet doors, providing lift assistance that increases as the door opens to counteract decreasing hinge leverage, with 80-100N recommended for doors over 700mm tall.

Overhead cabinet doors present a classic lift-assist challenge: the force required to hold the door open is greatest when the door is fully open (90 degrees) due to the horizontal center of gravity position. Gas springs naturally provide higher force at this position. For doors under 600mm tall, 60N struts often suffice; doors 600-700mm benefit from 80N; and tall pantry or wall unit doors over 700mm typically require 100N for reliable hold-open. Constant force springs would require complex lever or cam mechanisms to mimic this force curve, increasing cost and failure points. “In kitchen installations, I consistently see 80N gas springs prevent the ‘door drift’ issue that plagues cheaper 60N units after seasonal cabinet settling,” observes Reid.

Can Constant Force Springs Replace Gas Springs in Industrial Equipment Hatches?

No – constant force springs are unsuitable for industrial equipment hatches requiring lift-assist because they lack the stroke-dependent force increase needed to counteract changing mechanical advantage during opening.

Industrial hatches often feature heavy plates or access covers where the force to hold the hatch open varies significantly with angle. At 30 degrees open, mechanical advantage may require only 50N of assist force, but at 80 degrees open, the same hatch might need 150N to prevent drift. Gas springs automatically provide this increasing force profile through their nitrogen charge characteristics. Constant force springs would deliver the same 100N force at all angles – either straining the hatch mechanism at low angles or failing to hold at high angles. For hatches requiring precise positioning at intermediate angles, lockable gas springs offer superior control over constant force alternatives.”

How Does Temperature Affect Gas Spring vs Constant Force Spring Performance?

Gas spring force decreases approximately 1.5% per °C below room temperature, requiring derating in cold environments; constant force springs show minimal temperature sensitivity (<0.5%/°C) but lack lift-assist suitability.

This temperature sensitivity is a critical consideration for gas springs in outdoor or cold-storage applications. A gas spring rated at 100N at 20°C will deliver only approximately 85N at 0°C – potentially insufficient to hold a lid open. Constant force springs maintain force within ±2.5% across -20°C to +80°C ranges, making them preferable for applications like outdoor cable retractors where temperature extremes occur. However, for lift-assist applications where temperature sensitivity can be compensated through slight force uprating (typically +20% for -10°C operation), gas springs remain the technically correct choice. “Never specify constant force springs for a caravan locker lid just because of temperature concerns – the force characteristic mismatch will cause operational issues regardless of temperature stability,” Reid advises.

What Are the Failure Mode Differences Between Spring Types?

Gas springs typically fail through gradual nitrogen seal wear (reducing force over time); constant force springs fail through strip fracture or coil binding from misalignment or lateral loading.

Gas spring failure is usually progressive – you’ll notice the lid requires more effort to open or begins to drift closed over weeks or months. This allows planned replacement before complete failure. Constant force springs tend to fail catastrophically when the steel strip fractures from fatigue or when lateral loads cause the coil to bind and jam. In high-vibration environments like vehicle suspensions or industrial machinery, constant force springs require precise guidance systems to prevent premature failure, while gas springs tolerate minor angular misalignment better due to their piston-and-cylinder design. “In 15 years of specifying springs for UK manufacturing, I’ve replaced far more constant force springs due to misalignment damage than gas springs due to seal wear – but only when the application actually suited the spring type,” Reid states.

How Do I Size a Gas Spring Correctly for My Application?

Use the gas spring force calculator with your lid/panel weight, hinge distance, stroke length and mounting angle to determine the required Newton force range.

Proper gas spring sizing requires four parameters: 1) Load weight (lid/panel mass), 2) Hinge to center of gravity distance, 3) Mounting geometry (hinge to spring attachment points), 4) Desired opening angle. The force calculator automates the trigonometry involved in determining the perpendicular force component required at various angles. For example, a 15kg cabinet door with CoG 200mm from hinge, springs mounted 150mm from hinge at 30° angle, requires approximately 75N per strut for 90° hold-open. Attempting to size constant force springs for this application would require complex moment calculations at multiple angles and likely result in over-specification. Always verify your calculation against the force calculator – it’s the most reliable method for avoiding undersizing or oversizing.”

Should I Use One or Two Gas Springs for Symmetrical Lids?

Use two gas springs for symmetrical lids over 600mm wide to prevent binding and ensure even force distribution – single struts are only suitable for narrow or asymmetrical applications.

For lids wider than 600mm, a single gas spring creates uneven loading that can bind the hatch mechanism or cause premature wear on hinges and mounting points. Two springs provide balanced lift assistance and reduce stress on individual components. The force per spring is calculated as half the total required force, but always verify with the force calculator as mounting geometry affects the split. Constant force springs face similar width limitations – single units work only for narrow applications where lateral stability isn’t an issue. “I specify dual gas springs as standard for all automotive boot lids and cabinet doors over 500mm width – the marginal cost increase prevents the majority of field alignment issues we see with single-strut installations,” notes Reid.

What End Fittings Work Best With Gas Springs vs Constant Force Springs?

Gas springs commonly use ball socket, clevis or eyelet end fittings for pivoting applications; constant force springs typically require specialized spools or housings for linear extension.

Gas springs benefit from pivoting end fittings that accommodate minor angular misalignment during operation – ball sockets allow 10-15° angular freedom, clevis brackets provide pinned connections for higher loads, and eyelets offer bolt-through security. Constant force springs require precise linear guidance since any angular force causes binding or strip damage. Their end attachments are typically spools around which the steel strip coils/uncoils, necessitating housing designs that maintain perfect axial alignment. For most lift-assist applications where some pivoting occurs at the mounting points, gas springs with ball socket or clevis ends provide more forgiving installation than constant force springs requiring linear guidance systems. “In furniture applications, I always specify ball socket ends for cabinet door gas springs – the slight angular tolerance accommodates hinge settling over time without inducing premature failure,” explains Reid.

How Do Service Lives Compare Between Spring Types?

Standard gas springs last 20,000-50,000 cycles; high-cycle industrial gas springs reach 100,000+ cycles; constant force springs exceed 100,000 cycles in ideal conditions but drop rapidly with misalignment.

Gas spring cycle life depends primarily on seal quality and operating environment – nitrogen permeation through rod seals is the dominant failure mode. In clean, temperature-controlled environments, industrial-grade gas springs with sealed end fittings can exceed 100,000 cycles. Constant force springs theoretically offer longer fatigue life (>100,000 cycles) due to lower stress levels in the steel strip, but this advantage vanishes with any misalignment or lateral loading that causes edge stress concentrations. In real-world applications with minor installation tolerances, gas springs often achieve comparable or better service life due to their tolerance for angular movement. “For a pharmaceutical cleanroom hatch requiring daily operation, I’d specify a 316 stainless gas spring with sealed end fittings rated for 80,000 cycles – the constant force alternative would require precision guidance housing that increases cost and contamination risk,” concludes Reid.