Almax advise against anti-pinch pins

Shock waves? Huh? Sorry, a physics degree and a lot of experience says that's total tosh! Most people don't realise that bolt-cropping fundamentally involves a tensile failure. The jaws of the croppers are like wedges that are being forced together. That creates a tensile pull across the material between the jaws. If it is strong enough to resist that pull, it will not be cropped. If it isn't strong enough, that side of the chain link will tear apart and you can see the result if you look closely at the grain structure on a cropped face. Ductile materials will tear apart very easily so the grain structure is virtually invisible as it has been cut rather than torn apart across the centre. Harder materials tend to have more tensile strength, so that helps them to resist cropping, but if the ultimate tensile strength is insufficient for the croppers in use, it will still result in a failure, like a bolt when you over-tighten a nut. We are not really dealing with ductile materials here, at least we shouldn't be, as they are no good in security situations. Now, whether the other side of a chain link breaks after one side has been cut/cropped, is down to the tensile strength and stress concentrations brought to bear around the rest of the link. Any point where the sudden distortion of the cut side results in stress that is beyond the strength of the material will start another failure. Over-hard chains might be quite strong and fairly good at resisting the initial cut, but once that goes they often tend to result in an immediate fracture on the other side of the link as it is so brittle. Such inferior chains are often easily defeated with freezing & hammering attacks. The freezing increases the brittleness, and clouting it with a hammer results in it shattering. Whether the other side breaks immediately is a side issue, as a thief could easily crop that, second, side more easily than the first side anyway so if the thief gets through it once, he will very likely finish the job. Over-harness is more of a problem with thinner gauge chains as there is less metal there to give a good compromise between surface hardness (which you need to stop hacksaws) and core toughness, to give strength whilst resisting hammering and cropping. A simple mild steel chain might be case hardened to stop hacksaws, but its softness across the core means it won't have the tensile strength to stop croppers (and the lack of toughness across the section also means the case is not well supported and is more likely to collapse under the pressure from the jaws, and although that's a secondary effect, it combines with the weakness to make it easy to defeat).

I hope that helps to explain some of what this is about? I could go on, but many might say I already have :-)

Chains up in the air are much harder to attack than anything on or near the floor. A 2-pronged approach is often a good idea. A short, thick chain, to stop the croppers, and a longer thinner chain to stop other stuff being pinched, is a common strategy for pushbikes, for instance (with both chains going through the ground anchor).

U-Locks/D-Locks are most definitely vulnerable to levering and jacking attacks. If you have to use one, try to fill the space inside the 'D' to minimise opportunities for a thief to get a lever etc in there.

Chains are not vulnerable to the same kinds of attacks as D-locks, which is why we tend to think that D-locks are mainly relevant as a compromise for portability and, for back at home, you should normally use a chain and a proper padlock (and the D-lock as well if you've got it, but as an independent/secondary deterrent; _not_ tethering the chain).

Was that shock waves to your head?

This video, albeit by Almax themselves so far from objective:
https://www.youtube.com/watch?v=Cpf35C7wu6Q

illustrates how chains will do by very large hand croppers. As you can see, the guy has to use his entire body for some of these, using the ground to rest the other handle of the croppers on. If a chain is higher up, it'll be a lot harder to position the croppers properly to achieve this level of leverage. So, the chain off the ground (or, for example, a chain that only just fits between the wall and the bike so they'll have to crop between the wall and the bike) is a very good obstacle for hand croppers. Of course, for electrical ones or for grinding it's a lot less of an issue.

>cough<

The first one to realise they're both correct but one has defined 'shockwave' incorrectly.

Are you for real? I'd say I'd be believing what the bloke "with the physics degree" says about what makes chains break, shockwaves and the like, not because of his physics degree but simply because making these chains and lock systems and specifiying their hardness etc is *his job*.

You'd be a fool to believe any argument based simply on authority surely?

I'm confused now. (not hard, unlike Almax chains)

In all seriousness the Almax people themselves mentioned shockwaves - it's not something that just popped into my non physics degree head - otherwise I wouldn't have mentioned it.

Either way, I'll not be buying that blokes products, that he's indirectly trying to flog, because if I had to ask some stupid non physics degree type of questions I don't think I could put up with his patronising manner.

"Huh, shock waves? You stupid customer. Go away and think about what you've said but don't forget to go on our website, if you can manage it, and check out our new products!"

Is anybody going to actually explain this or is it just a smugness contest?