A couple of weeks ago I found a rack + crab in Black Shiver. If you are the unlucky owner of this gear:

a) The gear is now in Sweden, because I forgot about it until I found it in a bag when I unpacked.

b) It was found at the bottom of the Black Rift. On closer examination it shows some outward signs of having fallen a reasonably long way (i.e. fresh and fairly deep scratches, deformations to the aluminium etc.). Since this pitch is 80m, it would have been travelling at 40m/s on impact if it fell from the top (ignoring air resistance).

My suggestion is that I scrap the gear, but I don't want to do this without first posting. If you want it back, I can bring it to Britain on my next visit, but please bear in mind point (b) above. There were some coloured tape markings which you can identify the gear by.

Mark

If the owner doesn't want it back, perhaps someone else has the means to take a look at it/take sections/do some scanning on it, to see what damage really was suffered. We always assume that a long drop can render gear dangerous to use, but here is a chance for someone to do some destructive testing in a real case. Could be quite educational! Just how far do you have to drop a krab, for example, before you shouldn't really think of using it again?

Peter Burgess said:

Just how far do you have to drop a krab, for example, before you shouldn't really think of using it again?

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... when it lands out of reach and you can't be arsed to go and get it :wink:

Since material science is one of the main specialities at the university I work at, I can arrange for some tests to be done. However, it would only be worthwhile if we know approximately how far the gear fell.

Mark

However, it would only be worthwhile if we know approximately how far the gear fell.

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So if the owner can confirm this, then we have a mission!

I don't know the cave, but is it possible it fell anything other than the 80m you mentioned?

It certainly cannot of fallen more than 80m as this is the max height of the pitch (unless someone threw it down the pitch!), and maybe it didn't fall at all and that it was just left at the bottom. Destructive testing of this kind will conclude nothing as you nothing of its history and of the specific fall. If it really interests you just buy a new one and drop that! For the time and effort taken to test it there's no point in doing a poor test. Having said that it would be good fun.

I read a BMC summary of a technical report on this type of thing a few years ago, it related to dropping a crab a long way onto rock, and i think even at the equivalent impact of 100m the strength of the crab when loaded still far exceeded the minimum safety standard requirements. it was in summit somewhere, i'll look when i get home, or search for something on the web... If youve got the necessary equipment it would be intereseting.

Saying which i'm saf in a lab nect to the perfect machine for this too... only its a dental material lab, but i'll ask...

tt.

The aluminium alloy used to make rack bars seems to be softer than krabs. I think that's why a couple of the bars look kind of squashed on the corner. Only speculation though, since we have no details of history.

I agree with Rob and that's what I said in my earlier post - that it would only be worth testing it if the owner could confirm the length of the fall. Even then, it would not be a conclusive piece of evidence in itself as we have no idea which way up it landed or exactly what it landed on.

Hmmm, I don't think I would want to use this piece of gear though. It would be a bummer if it broke halfway down Titan or somewhere!

Mark