These results show a few very interesting points: Let's look at the average cutting lengths of the two different EDELRID ropes Swift Eco Dry 8.9 mm and the Python 10.0 mm loaded each time with 80 kg – trying to resemble the load of one person. We see that the 10.0 mm rope achieves a higher value than the 8.9 mm rope (22.7 % higher). Also shown here are the results cutting the EDELRID Swift Protect Pro Dry 8.9 mm rope at 80 kg of load, resulting in a much higher cutting length than both other ropes.
If the load is now increased to 160 kg resembling the weight of two persons we see a dramatic drop of the cutting lengths of both ropes (-77.2 % for the 8.9 mm rope and -78.4 % for the 10.0 mm rope). We also see that given the load of 160 kg the difference between both diameters is only 16.4 %.
Remarks on the results
Please have in mind that these results are laboratory results measured on a specific testing machine and set up that was built in order to get reliable, reproducible and therefore comparable results. Similar to the number of standard falls provided in the technical data of your dynamic rope, these values do not correspond to practical performances in real-life applications. However, the machine we designed to test the cut resistance on achieves results with reproducibility and reliability that has to our knowledge never been achieved before and are therefore the best way to get indications for safety-relevant questions.
Looking only at the results of the 8.9 mm rope compared to the 10.0 mm rope at 80 kg, one could initially assume what one might intuitively expect: a larger diameter provides greater safety in terms of cut resistance. Without first going into detail about our second parameter to be investigated, we can also see the result for a very new and special rope that is tuned to cut resistance – The Swift Protect Pro Dry 8.9 mm. It shows a significantly higher cut resistance than both other rope and only this, unfortunately, proves already that the parameter diameter might not be a good indicator alone to judge the overall safety of a rope system regarding its cut resistance.
But back to our initial research goal to compare the influence of diameter against the influence of the involved weight. With both shown results of the test comparing the two diameters at 80 kg and at 160 kg we can now put the two scenarios described in the introduction into perspective:
If we take the rope system of a small diameter like 8.9 mm loaded only with 80 kg (one person) and compare its cut resistance with a rope system with a 10.0 mm rope but loaded with 160 kg we get a very interesting and obvious result: