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Crag & Route Beta

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Topic Date User

Shackles and the sheriff of Shipley 21-Apr-2011 At 11:05:47 AM hotgemini

Message

Alright, lets talk some numbers.

For the sake of the discussion, lets start by defining our 'lowering units'. Assuming a linear relationship and we can define this as 1N.m of rope travel. (that is, one lowering unit, equates to a rope applying 1N of force to the anchor travelling 1m). So an 80kg climber being lowered 15m would generate 23544 lowering units (9.81 x 2 x 80 x 15)

For the sake of the discussion, I'm naming 1000 lowering units a 'bellchamber' (to be clear 1 bellchamber = 1000 lowering units) and we give it the symbol of kJ. So lowering off is taken at 23.5 bellchambers.

For useful comparison, abseiling off a route and then pulling the rope (assuming a near worst case scenario of a 70m, 11mm rope, fed to exactly halfway through the anchor) would generate approximately 0.64 bellchambers.

For the pedants (eg. me) we could even then work out the wear caused by the 'unladen' rope running through the fixed hardware while a top-roped climber ascends the route. (about 0.175 bellchambers)

So for the sake of generating some numbers, lets say that a typical group at shipley might be four friends who each attempt the route twice.

If they all top-rope directly through the fixed hardware we have 8 lowering cycles totalling 188 bellchambers. If we say that there is 5 groups like this a week on jack high, 52 weeks a year. So an annual wear rate of 48,880 bellchambers.

So based on my experience with KP anchors and for the purely comparative purposes of this essay, lets peg the lifespan of an anchor at 100,000 bellchambers. So we've got an anchor life of 2.04 years and as discussed earlier, we're looking at Linze donating about $4000/annum.

If we can convince that group to change their climbing habits so that only the final climber lowers off. That number jumps to an anchor lifespan of 16.36 years and Linze's annual donations to hardware can be reduced to around $489.

If say, half of the routes, are able to be safely/comfortably cleaned on abseil, rather than being lowered and we can convince climbers to do so, then the average lifespan goes out beyond 30 years and Linze's anchor donation drops to $262.50.

Now, going back to the second last example. If say one of those five groups top-ropes through the hardware, rather than using their own draws our anchor life drops back to 6.8 years.

So cliff notes version, just one in five groups of climbers toproping through the fixed hardware results in a ~60% reduction in anchor life.

-Adam.