Gas struts or springs are used in caravans and RVs for helping to lift and
hold heavy things like the roof of a pop-top or an island beds for storage.
There are many types of Gas Struts and it is important to use the right one.
This is a quick guide to help you choose.
How Are Struts Measured?
The main things that vary between the Struts are the Strength, the Extended
Length, and the Compressed Length. Other things that may be a choice are the
Shaft size and the Ball Joint size. The most commonly used ball joint on RV's
On this website we name our Struts with a format like:
Gas Strut, 525mm > 305mm, 350N, 8mm Shaft with 10mm Ball Joint
In this case the
Extended Length = 525mm
Compressed Length = 305mm (Extended - Stroke)
Strength = 350N (which is about 35kg)
How To Install.
In the below example the uncompressed strut is 130mm. The position of the fixed
end is around 130mm from the hinge point.
If the strut can compress by 50mm then
the moving end can be mounted up to 50mm from the hinge. The further away from the hinge point the less it will open but the push will be stronger.
How To Change Ball Joints.
Ball joints and brackets of the same size are interchangeable. Sometimes your gas struts may be delivered from us with the ball joint pre-installed into the socket.
We are often asked how to remove the ball from the socket to enable the use of the brackets we offer. There can be black plastic ends with a metal surround that needs to opened or the spring steel retaining clip that is holding the ball firmly in place.
Carefully use a small prying tool. A small flat blade screw driver works best as you can twist the blade to remove the clip easily.
How To Work Out What Strength You Need.
If you are replacing an existing strut the strength (N) should be printed on
the strut you have. Otherwise...
The easiest way to guess the lifting weight required for a gas strut, is to
use a set of bathroom scales, and length of timber.
Pick the position where you think the gas strut will be located and place the
timber and scales there. This will show you the weight that is being applied
in that position. If for example the scales read 20kgs then you need at least
a 200N (20kgs x 10) strut to hold the weight.
Remember to take into consideration any extra weight such as a mattress.
It is important to select the correct length of strut that will open to the
desired height, but also allow the stroke to fully close.
Advanced: The Scientific Method.
For those who would like to try a more mathematical approach to working out
the strength then please study the formulas presented.
F1 = G x XG
F2 = A x F1 x LS
Z = length of lid from pivot (hinge) point in millimetres.
XG = Centre of Gravity in millimetres.
G = The weight of the lid in Newtons. 1Kg is 9.8N
(Round this to 10 Newtons).
LS = Radius of Gas Spring Force in millimetres.
A = Number of gas springs per application. We recommend
using two for most applications such as island beds
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