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K-Factor (Gas Spring Rate)

Gas Spring K-Factor (Gas Spring Rate) is the ratio of the compressed force (P2) and extended force (P1) expressed as P2/P1.

As governed by Boyle’s Law, P2 force is always greater than P1 force. During spring compression, the volume of rod introduced into the cylinder displaces an equal volume of gas, increasing the pressure in the cylinder and therefore the force of the spring. IGS standard springs are manufactured to uniform K factors for each size (determined by rod diameter). These factors are generally:

Type 4 1.2 Type 10 1.3
Type 6 1.2 Type 14 1.5
Type 8 1.3 Type 20 1.4

K- Factors can be increased or decreased to optimize performance See the following section on modified K factors.

Modified K-Factors

The design of a gas spring can be modified to support applications requiring lower and higher K factors. Low K factors where the extended and compressed forces are almost equal are desirable on straight vertical lifts and on vertical access panels that are hinged on the top. High K factors are useful when more P2 force (compressed) is desirable in relation to the P1 force (extended). An example is a horizontal cover opening to 90 degrees where a high force is required to assist in the initial opening and little force is required to maintain the cover at the 90 degree position.

K factors are modified by either increasing or decreasing the length or diameter of the tube or by increasing or decreasing the diameter of the rod used. All affect the relationship between the volume of gas in the cylinder and the amount of gas displaced as the spring is compressed.

IGS manufactures a range of gas springs with different rod / body combinations to achieve lower and higher k-factors. See Products sub menu Custom Made Gas Springs

Below is a photograph of a spring with a .24” rod and 1.57” body that yields a K-factor of 1.04. This extreme example was used to visually illustrate the concept.


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