augustinmoinat / backupfall-html-js Goto Github PK

I have a fairly trivial case that produces an odd result in the simulation.

Steps to reproduce:

1. Configure a webbing type "Polyester", 50 g/m, stretch 1.5% @ 5 kN (stored in the browser as myWebbings: {n:Polyester,w:50,s:1.5,t:5})
2. With that webbing, create the following setup: main 100 m, backup 105 m (stored in the browser as MySetupBugreport: Polyester;100;Polyester;105)
3. Set gap length to 100 m, height zero on both sides
4. Set Desired tension to 2 kN, click Adjust from left side (the green box says "you have pulled 0.57 meters on the left")
5. Set Distance from left anchor to 20 m, leave other slackliner data at defaults
6. Run the model

Output of the model under Initial position:

The tension with the slackliner on the line is 3.51 kN on the left side and 3.45 kN on the right side.
The height of the line with the slackliner is -3.84 m, who is 19.72 m from the first anchor.
At least one section of backup is engaged when the slackliner is on the line

The thing that seems odd is the last line of that output: At least one section of backup is engaged when the slackliner is on the line. With an backup excess length of 5 m, I don't see how that could be the case. The approximate length of the main webbing spanning the gap can be estimated from the calculated geometry (Pythagoras), and comes out to about 100.5 m. This is nowhere near the length of the backup (105 m).

Curiously enough, if I set Distance from left anchor to 50 m, I get the following output:

The tension with the slackliner on the line is 3.88 kN on the left side and 3.88 kN on the right side.
The height of the line with the slackliner is -5.42 m, who is 50.00 m from the first anchor.

In this case, there is no notice about the backup engaging, despite the fact that forces on both sides are now larger than they were before. Clearly if the backup was indeed engaged in the previous case, it should have been even more so in this one.