/ Tyrolean traverse setup
Def check the anchors. Different forces involved
This explains quite well: http://www.chetwynd.info/other/anchors.htm
According to the formulas with an 80kg person in the centre of the traverse, rope straight between the two anchors and minimal rope/cable stretch the anchors would be experiencing in the region of 1130kg (11.1kn) each, and the rope/cable would be experiencing double that... 22-26kn is the kind of breaking strains I found by doing a straw poll of several brands of (10.5mm) static rope*, so you'd have a very small to totally negligible safety margin.
*with 12mm things get a little better with upto 36kn braking strains available, which may be all right, but it's a comparatively specialist product.
As mentioned, the load on the anchors can be massive, though it reduces by the bigger the sag you have in the line. (which can then create the problem of too much sag if you reduce the angle too much).
I think the optimum angle is 150 degrees at the centre (taking a completely horizontal traverse line to be 180 degrees:- i.e. 15 degrees off horizontal at each side). But this still puts double the weight of the load on each anchor.
Have a look at this groovy little calculator to show the effect on the anchors at different angles. Adjust the weight you want at the bottom and move the wee weight up and down to alter the angle and it shows you the effect the different angle has for whatever weight you select:
> Have a look at this groovy little calculator to show the effect on the anchors at different angles. Adjust the weight you want at the bottom and move the wee weight up and down to alter the angle and it shows you the effect the different angle has for whatever weight you select:
That's great, thanks for sharing.
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