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  • Optimal angle for weight to be applied to a shock

    Discussion in 'Calculations' started by Barbarian, Dec 9, 2013.

    1. Barbarian

      Barbarian Active Member

      Sep 2013
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      I have a small shock that needs to support few hundred pounds. The designer who came up with it made a major flaw in part design so the pressure on the shock is too shallow instead of weight applying from point to point most of the pressure goes right in the middle of the shock causing it to bend and making it useless. My question is how do i calculate the correct angle for the shock to work properly? Im industrial Designer. I cant post picture now but will post when I can.

    3. Lochnagar

      Lochnagar Well-Known Member

      Feb 2011
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      There are a few iterations here to solve the problem - since usually there are geometry constraints that dictate where the gas strut can be fitted - versus what size of gas strut you can buy - versus the closed / and open angle of the system.

      So to start the iteration process:

      1) The first thing you need to do is draw a free body diagram of the problem - with all the forces acting on it. From this you should be able to compute the gas strut force required in the both the closed angle and open angle of the system.
      (I sense from the picture you have posted above - that it is maybe upside down - since gravity would want to hold the horizontal member down - not up).

      2) The second thing you need to do is pick a gas strut of sufficient capacity to do the job - from the results you get from step 1 above. However, it is likely that the gas strut will not fit into the exact locations you envisaged in step 1 above. Therefore you need to find a gas strut that will "do the geometry".

      3) The third thing you need to do is ensure that the gas strut is capable of holding the horizontal member in your diagram - when your horizontal member is in the open position - which is usually what you want to do.

      You need to keep going round the three steps above - until you have got an optimum solution. If you have a look at the two links below for some inspiration on the geometry layout.


      Last edited: Dec 12, 2013
    4. ChrisW

      ChrisW Well-Known Member

      Jun 2012
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      If the shock is correctly rated for the applied load but suffers buckling failure, it is more likely that the combination of a wide range of rotational movement over the full stroke and friction withing the end bushings is causing a torsional load to be applied to the shock.

      In your arrangement there is no side load on the shock, it is purely axial. I suggest you try a low friction joint at either end, spherical ball joints are commonly available, which will reduce any torsional loading to the shock.

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