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Help Selecting The Correct Gas Strut.

Article by CaravansPlus - Caravans Plus

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 are 10mm.

On this website we name our Struts with a format like:
Gas Strut, 525mm > 305mm, 350N, 8mm Shaft with 10mm Ball Joint Ends.

In this case the
Extended Length = 525mm
Compressed Length = 305mm (Extended - Stroke)
Strength = 350N (which is about 35kg)

Selecting The Correct Gas Strut


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.

Circlip on Ball Joint

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.

Selecting The Correct Gas Strut


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

Selecting The Correct Gas Strut

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14 Comments

  • comment-avatar

    Vanya

    I want to add 2 gas struts to my 2013 A Liner roof but don't know what length or strength to use I hope you can help me.

  • comment-avatar

    kevin

    what size struts to lift roof coromal mirage roof 396 mod

  • comment-avatar

    Clive

    Hi Kevin, my Jayco ones had a serial number on them which provided the right lift strength

  • comment-avatar

    Steven Butcher

    I am a vehicle builder by trade. Usually just buy the replacement for the part without much thought. This site is extremely helpful as I am now fitting struts to tool trailers that have very heavy steel doors 1800 long x 900 wide. doors physically lifted up toopen position by han and a steel rod "prop" put in to position. Very unsafe to remove rod and then lower by hand. Knowing how to calculate which strut is going to lift and hold the weight is very helpful.

  • comment-avatar

    Geoffrey

    Hi there, Hope you can help, please... new to gas struts... recently purchased 2 x 350N struts for a special project at home (to crazy to explain!!). The struts seem to be jammed open and I can't compress them at all. 2 questions : 1/ Can a 100kg guy compress a 350N strut or is the strut to powerful? 2/ If I stick the struts in the fridge will this cool the gas (and thus reduce pressure) so that then the strut can be compressed somewhat? Will look forward to your answers, if possible, thanks again, Geoffrey.

  • comment-avatar

    George Drew

    Hi Geoffrey - please don't freeze them! If you can't compress the struts with gentle hand pressure, your lid, or whatever you are trying to lift) is too light. Follow the formula on this website, and you will get a better idea. WARNING: Please don't mess with gas struts - they are very powerful and can cause serious injury. If you try to compress them incorrectly, you can also blow the seals rendering them useless. Cheers.

  • comment-avatar

    Geoffrey

    I have the same problem how do you compress? if i cant compress then when i go fit them they will stay jammed ???? how do you free them help please If i go ahead and fit them to my Pop Top then the weight of roof should close them? 470N struts

  • comment-avatar

    John

    Hi, Regarding gas struts for my caravan bed. We have added a mattress topper which has been very successful, but the current struts no longer hold up the bed. The current struts have the following detail printed on the cylinder: YQ-8-18-450N. Is this enough to identify a suitable replacement? I was thinking of increasing the replacement to about 500N if possible.

  • comment-avatar

    Alan Fields

    I need to replace the existing struts on my caravan bed. I found the following number on the strut but I am not sure its relevant. 7644WN0290N. My caravan is a Coromal Element 632 with a queen bed. Can you please advise if you can direct me to the correct strut.

  • comment-avatar

    Doug

    I think there is something crucial missing from these formulae and their explanation. What is F1 and what is F2? What am I actually supposed to be calculating here? If I use the formulae as you have explained them, I have an answer of 120,000,000!! 120 million "whats"? Please forgive my cynicism but I feel this is probably not right.

  • comment-avatar

    James

    I agree. I weighed my door at the out most edge and recorded 11 kg at 1600mm from the hinge. I will use a pair of 600mm gas struts with 250mm throw, supporting the door at 200mm from the hinge. The effective weight at 200mm is not simple to calculate. You have to sum moments around the support point and find the hinge is pushing down with 66kg plus the weight of the door at 22kg gives 88 kg. But that's not all... The gas strut pushes up at an angle of 19.47 degrees, so the effective force must be 88 / cos(19.47) = 93 kg, or nearly 930 N. The gas struts I ordered support 800 N each, so I should have to push pretty hard to close the door - which is good because it is a door on a chicken caravan and I wouldn't want the wind to blow it shut!

  • comment-avatar

    Don

    Roof Struts on my 2001 jaco have 281384 330N 03/01 on them can I order them with that ??

  • comment-avatar

    Adam

    Hi, I have a 2010 Jayco Expanda 16.49.3 with roof top A/C and need to replace all 4 struts for the roof. The ones on the van are made by Stabilus with part No 8672ZM 500N 326/10. Do you have these in stock or an equivalent one? Cheers Adam

  • comment-avatar

    Jennifer

    What struts would I need to lift my 14foot viscount poptop roof 1987 ultralight. It has no air con on it. We have the scissor lifters but want to replace them. Thank you

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