Problems & mistakes to avoid
What can happen with a wrong gas springs calculation
On the Internet, many sites offer tools for calculating gas springs. What looks so simple on theory can lead to several problems in practice. This is because there are many parameters that have to be taken into account in a gas spring application, and even small deviations can mean that the gas spring does not function properly or even poses a safety risk.
These examples show what can go wrong when gas springs are calculated incorrectly.
Counter flap falls shut unhindered despite gas spring
Counter top flap should remain open and not slam shut when closing
To make it easier to open a counter flap, they installed a gas spring from a different manufacturer. Unfortunately, it only solved part of the problem. The customer contacted us with the following description of the issue: “Opening the flap with the gas spring is fine. But unfortunately the flap slams shut from an angle of approx. 35°, and hence there is a considerable risk of injury.”
Another problem: the flap did not stay in the open position, but rather closed again a bit, which made it difficult to pass through.
In this example, the previously installed gas spring had to be discarded. The customer ended up paying twice and it is not a sustainable solution for the environment either.
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Bent gas spring
Bending hazard of gas springs: too long stroke with too small a diameter
You would like to have a modern work of art? How about the “bending gas spring” design?
What went wrong with this gas spring? The diameter of the piston rod and cylinder was too small for this application with a relatively long piston rod. This, coupled with correspondingly high pressure, can lead quite quickly to bending of the piston rod.
If it really is not possible to choose a gas spring of a larger diameter series, then the piston rod must have a guide.
Too long a stroke at too high a pressure and too small diameter of piston rod and cylinder… and the artwork is done!
Floor hatch opens at full speed and rips off gas springs
Gas springs cannot be used as an end stop – and certainly not if the gas spring extends without damping
In this example, two factors came together:
- Gas springs with damping type 0 were used, i.e. the piston rod extends completely without braking. If there had been a stop, the flap would have hit this stop with full force and possibly bent it.
- In this case, however, there was no mechanical stop either, so the gas spring opened the lid at full speed.
The inertia of the lid caused it to open further than the stroke of the gas springs actually allows. The combination of the lack of control of the opening speed and the lack of an end stop resulted in such high energies that the piston rods of the gas springs were torn out of the cylinders after only a few actuations.
So it’s not just a matter of calculating the forces. The installation conditions and knowledge of other capabilities of a gas spring are also necessary for its correct design. Only in this way can a gas spring be a reliable, long-lasting helper with perfect function.
Saving on gas springs for this large bottom flap leads to deformation
Large, wide flaps – in terms of force, a single gas spring might be enough, but that’s saving money in the wrong place
A single gas spring can certainly open and hold open a flap with a depth of 1450 mm and a width of 3,000 mm and a weight of approx. 100 kg.
BUT:
Proper function also means that the flap should close completely. And, if they are flaps in the floor, then this is even more important, otherwise they pose a tripping hazard.
Why can a single gas spring cause the flap to still remain open a bit on one side?
If the gas spring on a large flap only presses on one side, the flap may warp over time. This may also affect the hinges. And at the point where the gas spring is attached, the flap then stands up a bit.
At DICTATOR, we are very good at assessing the flap dimensions from which 2 gas springs absolutely have to be used and where one gas spring is still enough in order to achieve the optimal result.
More examples
It happens again and again that the design of a flap has to be adapted a second time. In this case, the weight and length of the flap changed after the gas springs had already been ordered and delivered.
The gas springs for the flap originally planned were calculated to be able to hold the flap both closed and open, and to allow it to be comfortably handled by one person.
What would have happened if the gas springs had been installed at the previously calculated points despite the change in the weight and dimensions of the flap?
If, after changing the weight of the flap, the gas springs had been fixed at the installation positions determined in the first calculation, the flap would never stay closed. Even if it were pressed into the closed position with (very high) manual force, it would immediately bounce back up with a force of 141 N after release.
What to do now? Throwing away the gas springs would be an expensive waste of material and resources, which would not be in line with DICTATOR’s idea of sustainability.
So DICTATOR revised the original calculation (free of charge!) – taking into account the gas springs already supplied – and calculated new installation points, some of which differed considerably from the original ones.
The customer was thus not only able to continue using the existing gas springs – he also saved himself a laborious “approach” to the correct fastening points in the course of “trial and error”, which would have been very time-consuming and possibly also would have turned the profiles of the flap into “Swiss cheese”.
The whole calculation of gas springs and fixing points based on the original customer request.
After changing the size and weight of the flap, it was possible to recalculate the fixing points so that gas springs previously purchased could still be used.
