How To Calculate Gas Strut Position

In our previous articles, we covered how to measure gas struts and how to install gas springs. Today, we’ll show you the gas spring installation calculation, as they say, Give a man a fish, and you feed him for a day. Teach a man to fish and you feed him for a lifetime.

The calculation method is also very simple and will be explained in three steps.

1. Determine the Extended Length

When choosing gas struts to keep the trunk, hood, fishing rod locker, windows, benches, or storage boxes open, let’s illustrate this with the example of opening the hatch to a 90° angle. For the gas spring extended length, we can estimate it to be about 60% to 70% of the hatch height. For example, if a hatch door is 30 inches high, then suggested lift supports extended length of 18~21 inches are suitable.

2. Determine the Ideal Mounting Position

For gas shocks of various specifications, we have detailed the specific mounting position that we consider optimal in the installation instructions. In practice, it’s important to note that the installing position is not the only option, you can adjust them based on our needs and different situations. In general, the distance from the upper installation point to the hinge (a) should be shorter than the distance from the door’s center point to the hinge (b).

3. Determine the Force

After determining the gas spring’s extended length and mounting position, we can calculate and confirm the required gas spring force (F).

To ensure gas struts last longer, it’s important to select a pair that distributes force evenly and avoids strain. In the figure below, we have marked some installation points.
A: the top mounting point of the shock;
B: the installation point of the box hinge;
M: the center point of the door height.

Additionally, you can refer to the explanations of the labeled letters in the lower left corner of the image.
Letter ‘a’ : the distance from the top installation point A to the box hinge (B);
Letter ‘b’ : the distance from the center point (M) of the door height to the box hinge (B). This distance is equal to half of the door height;
Letter ‘c’ : the distance from the bottom installation point to the hinge (B);
Letter ‘G’ : the gravity of the door, expressed in Newtons, i.e. G = mg = m * 9.81.

Please note that the units for ‘a’, ‘b’, and ‘c’ are all in inches. The calculation formula is F = G * b / (c * 2).

Next, I will demonstrate the calculation using an example.
Suppose we have a cabinet with a door height of 15 inches and a weight of m=10kg. We need to place it 1/3 of the door height from the hinge. The measurements are:
a = 15 * 1/3= 5 inches ;
b = 1/2 * door height 1/2 * 15= 7.5 inches ;
c = 22% * 15= 3.3 inches (c is approximately equal to 20%-25% of door height).

As we mentioned before, gas strut’s extended length can be about 60% to 70% of the hatch height. Therefore, L 1= 60% * 15= 9; L 2 = 70% * 15 = 10.5.
Thus, we can choose a gas strut with a length between 9 to 10.5 inches. F = G * b / (c * 2)= 10 * 9.8 1* 7.5/ (3.3*2 )=735.75/6.6 ≈ 111N

From the given information, we require gas struts that have a force of 111N. In this case, we can directly choose a pair of Apexstone 10-inch 100N gas springs, which will help us easily lift the cabinet door. For greater support, it’s advisable to install the piston shocks in a more vertical orientation.

If you find the calculation process too complicated, you can now use our new gas struts calculator for an easier solution. Just enter 3 simple pieces of information, and it will quickly provide you with the gas spring size you require. It’s simple, convenient, and completely free to use. Please understand that there is a margin of error in this calculation result. We have practiced it extensively and consider this method quite reliable. It can help you choose the right gas struts for effective door lifting, even if you lack prior experience. If you have any questions, please don’t hesitate to email us at [email protected], we’re here to discuss and assist you.

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