# _3D-printed SOF-T-like tourniquet_ - Tests results
_\[**English version automatically spell checked with minimum effort put into proofreading**\]_
## 1 - Explanation of the test
We don't have access to a dynamometer or a tensile testing machine _yet_, so we put the tourniquet between two strongly connected metal bars, and turned the windlass until we couldn't anymore.
The tourniquet we tested this way wasn't the full recommended spec :
- The infill was 60% gyroid.
- The layer height was 0.3mm.
- The sewing was done with thin coton thread, and the tension of the sewing machine was messed up.
The fact that even with a less than ideal tourniquet we didn't achieve failure by tensioning the tourniquet as the force requiers to add more tension was too much is very encouraging.
However we can't actually asses our tourniquet until we test the actual up to spec tourniquet, and test the tensioning force with a dynamometer and the tensile strength and failure force with a tensile testing machine. If you have access to these machine, please contact us at [distorsion@systemli.org](mailto:distorsion@systemli.org).
## 2 - Testing results
After tightening the tourniquet by hand between the two bars using the double-D, we tarted turning the windlass. After 6 half turns of the windlass it was impossible or us to turn it anymore with a single hand. Note that this is an unrealistic amount of tension as a limb would be less rigid than to metal bar, and in actual use we wouldn't have both hands and our body weight to turn the windlass.
### 2.a - After 6 half turns
After 6 half turns, we see in the above picture that there is no visible deformation in any plastic pieces, and the webbing is passing in the correct manner through the double D.
Note that we can see that the seam is already visibly deforming due to the poor sewing job. However no seam failed throughout this testing which is encouraging.
We recorded the sound which was produced when strumming the webbing, which you can listen to at [../pictures/sound/tourniquet_testing_6_half_turns.mp3](../pictures/sound/tourniquet_testing_6_half_turns.mp3). The goal of this ound is to give a sense of the tension produced by the tourniquet, and to qualitatively prove that the tension went up when doing additional half turns, as the pitch is going up.
### 2.b - After 7 half turns
We don't see any major deformation after an additional half turn, even though turning the windlass was very hard.
We can ear in the recorded sound - which you can listen to at [../pictures/sound/tourniquet_testing_7_half_turns.mp3](../pictures/sound/tourniquet_testing_7_half_turns.mp3) - that the tension increased after an additional half turn, which suggest that there wasn't any major slippage of the webbing through the double-D.
### 2.c - After 8 half turns
At this point we can see a deformation of the "top" D of the double D, which is starting to deform and slide inside the other D. This could cause slippage with higher tension, even though we didn't observe any, and there wasn't any critical failure of the double D (which could be attribuable to the mechanical property of PETG, which tends to bend rather than break).
Once again the recorded sound - which you can listen to at [../pictures/sound/tourniquet_testing_8_half_turns.mp3](../pictures/sound/tourniquet_testing_8_half_turns.mp3) - shows that the tension increased and there wasn't any major slippage as the pitch went up.
## 3 - Aftermath
After 8 half turns and a ~30min period of maintained tension, we unwound the windlass to inspect the tourniquet.
We see in the above pictures that the webbing was greatly deformed around the windlass were it was wound, and around the end of the strap where the webbing passed through the double D. Note that this webbing is rated for 306Kg, even though this weight is in tension, this can give us an idea of the force that the webbing supported for such deformation to occur.
We also show a closeup picture of the double-D and windlass holder which shows that one of the D and the windlass holder sustained no to very small deformation, while the "top" D sustained a large irreversible deformation, however without other signs of failure (like layer delamination or perimeter wall/shell separation).