Some accidents happened due to failures of steel wire cables. In my opinion this is easy to prevent, because "a cable dies slowly". We do not have a sudden overload in ropes courses. One common reason for a breaking steel wire cable is cyclic bending.
My previous experiments with cables in my cyclic bending machine were conducted in a quite unrealistic angle of about 100 degrees and more. This was done to learn about mechanism and principles.
Now it was time to test under realistic conditions. From my experience it is 45 degrees (from the horizontal). I took a 6x19 (fiber core) cable which is much less resistant than 7x19.
The complete assembly looks like this:
On the left side is 45 degrees - this is the interesting position. In the picture above it is loaded with 80 kg, in the picture below unloaded.
Lets move it ...
After 10.000 cycles there were little signs of damage:
One wire was obviously displaced.
After dismounting it looked like this:
About 6 broken wires.
You can hear some wires snapping - about one strand.
But the whole damage is uncovered by the load test:
The breaking load is only 29 kN, which is only half of the strength of an undamaged cable.
This shows that the damage to the wires is bigger than you can see on the broken wires.
A cable where I grinded one strand has 51 kN breaking load!
By the way: The damage on the other side (135 degrees angle) was terrifying:
The braking load was only 17 kN ... we are getting closer to real loads in a ropes course.
Therefore:
1. If you see a "loose" wire next to a clamp: Open it, try to bend the cable.
2. Clamps that create a cyclic bending should be opened every 10.000 participants, like the following situation.
Below it can look like this (same situation, another place):
