Gas Springs come in many different types but they all share the same basic principles of kinetic versus potential energy. To understand how they work, it is important to first understand what is actually inside the spring.
Anatomy of Gas Springs
All gas springs contain a chamber that stores nitrogen in what is called a pneumatic chamber. This chamber allows for pressures from as little as 10 pounds to as much as 450 pounds (or more) of potential energy to be stored in the spring. The other main area is the hydraulic chamber where a well-oiled piston can slide in and out to give the spring is extended and compressed length. At the very bottom of the chamber is a seal to keep the oil and nitrogen inside the spring.
The fascinating part of this process is that the gas spring can be designed to hold up an incredible amount of weight while only occupying a small physical footprint. All of this without any electronic or computer hardware; nothing but mechanical parts.
Measuring Gas Springs
There are quite a few different metrics when measuring a gas spring, the but the 4-main metrics are listed below:
The extended length is the simplest to measure as it is the distance between the center of the mounting holes on each side. We use measurements in inches as our manufacturer is in the US but I am sure metric is used in other parts of the world.
The compressed length is also measured as the distance from the center of the mounting holes on each side. Measuring the compressed length is only possible if the spring is completely worn out or it is possible to measure while on the lid that is closed. Most of the time, the compressed length is estimated.
The best way to get the pressure of an existing gas spring is to read the pressure off the label. If the numbers are still readable (often they have been worn away), the force will be measured in 1 of 3 different ways. You will either see a number followed by lbs. or #. This is the pressure in lbs. You may also see a large number like 433N which is pounds expressed in newtons. A quick conversion is that 1 lbs. is about 4.4482 newtons. Use this handy online conversion tool to convert newtons to pounds.
The only other way is to estimate the force but take special caution not to over or under-estimate the pressure. Sometimes there is no other way.
Most gas springs come in 1 of the following end types:
|Type A||Type B||Type C||Type D||Type E|
|10mm Plastic*||10mm Steel*||Blade Style||xxmm Steel||13 mm Steel**|
* 10mm is the most common design used for most universal applications.
** 13mm is the most common style used for 28" extended length lift supports.
Since a gas spring is 100% mechanical (no batteries or computer controlled hardware), ever wonder how a door closes slower as it reaches its final resting point? You probably guessed that as a spring extends, the pressure becomes less and less and that contributes to slowing of the spring extension as it reaches its destination. This is correct, but it is only half the equation. Gas Springs have a “bore” at the top of the piston that allows the oil to move from the bottom to the top of the chamber. Depending on the viscosity of the oil and the potential energy in the chamber, the acceleration of the piston changes as the spring extends.
The Death of a Gas Spring
Although gas springs are tough, the physical demands of the nature of its job and temperature changes can take a hefty toll on the hardware. Even under perfect conditions (defined by correctly fitted and matched springs for the application and mild temperature changes), gas springs will lose 1 to 2 percent of their pressure per year. Much like a hydrogen balloon or car tires lose their pressure over time or temperature changes, the same thing happens to gas springs. Not much can be done about this.
Poorly manufactured gas springs can fail much quicker. The most common failure is when the seal leaks and oil will run down the shaft. This rarely happens with our springs as ours are manufactured in the U.S. under the tightest quality control available.
A well manufactured gas spring should last 5 to 7 years under correct and normal usage.