Gas Strut - ideal mounting position & Force Calculation

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Discussion Overview

The discussion revolves around the ideal mounting position and force calculation for a gas strut used in a construction involving a top-opening frame made from aluminum extrusion. Participants explore the mechanics of strut placement, force requirements, and the implications of different mounting angles.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant describes the construction details, including dimensions and weight, and seeks advice on strut placement.
  • Another participant requests visual aids to better understand the setup.
  • A participant mentions the need for an adjustable air spring and suggests removing pressure to achieve the desired force.
  • Some participants propose that to maximize strut effectiveness, the bottom mount should be positioned further from the hinge and the upper mount should be kept away from the hinge as well.
  • One participant expresses a need for less force when the lid is open, indicating that the bottom bracket should be closer to the hinge.
  • Another participant explains the mechanics of force decomposition and moment calculation, suggesting a method to evaluate the adequacy of the strut force based on the lid's angle.

Areas of Agreement / Disagreement

Participants express differing views on the optimal mounting position for the gas strut and the implications of the lid's angle on the required force. There is no consensus on the best approach, and multiple perspectives on strut placement and force calculation remain present.

Contextual Notes

Participants mention various assumptions regarding the effectiveness of strut positioning and the calculations involved in determining the necessary force, but these assumptions are not fully resolved or agreed upon.

Vatech
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TL;DR
A pair of gas springs is needed to be installed on a top opening aluminum extrusion frame.
The position methods differ. Motion results also.I am a computer engineer, this is out of my field so i would be thankful for some help.
I have a construction made from 4040 aluminum extrusion.
The top frame is opening at 90deg with external hinge.
the weight of the top is 6Kg
The dimensions are 50X75cm externally
and 42X67 internally (as the frame width is 4cm)
If pictures with dimensions would help please let me know.
 
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Vatech said:
If pictures with dimensions would help please let me know
Yes, please. Diagrams/pictures always help. :smile:
 
I was kind of in a hurry so i designed the basic structure to be able to select the stroke and length needed.
i found that a total legth of 342mm hardly matches, so the next length i found is 402mm which fits easilly.
About the force i though of buying adjustable air spring and remove pressure until i get the expected result. What do you think?
Also, thank you for your time.
 

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"Ideal" mounting position... It's not all that clear to me what you're asking.

To maximize the effectiveness of strut force, you'd want to increase the angle (i.e. move the bottom mount further towards the front of the enclosure) and keep the upper mounting point far away from the hinge...

In your drawing, it looks like the bottom mount point is quite close to the lid hinge. when the lid is closed, the force vector would be practically aligned with the surface of the lid, instead of perpendicular to it...

With enough force from the strut, the two positional considerations I mentioned above don't matter much.
 
I need less force when the top is in open position . This means that the Bottom bracket of the strut would be reasonable close to hinge. When its in close position Yes , logically to be aligned with the top bracket would not help, that's why i is some cm below .
I am not an Engineer, that's why i come here for help.
By search on different installations i fould that on top opening applications they use that layout of bracket positions.
Just for reference :

 
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Because the angle of the lid is changing, there will almost certainly be less "opening" force when the lid is opened, compared to when it is closed.

The way you would check the adequacy of the force of the strut, is by decomposing the weight of the lid and strut force into vectors perpendicular to the lid and taking the moment about the hinge. Moment = force x distance. So you'll have something like mgcos(a)*d1 = F(strut,perpendicular)*d2.

The perpendicular component of the strut would be Fsin(b) as I have it drawn here, but it might be easier to define it from a different angle, depending on your actual placement.
1617279961260.png
 
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