Almax advise against anti-pinch pins
Discussion
Oh dear, I stand by my point that shockwaves are not relevant in the case of a boltcropper cutting a chain, but I did not mean to sound patronising, so apologies for that (I should have known better).
I was trying to explain what actually happens, and the propagation of stress around the chain link, which will involve shockwaves :-) **after** the initial failure of one side of the chain link is missing the point.
The link has already been cut on one side and, as I tried to say before, it is a very good assumption that the other side of the link will fail. A decent chain will need a second cut to get through the other side of the link, and an over-brittle chain will likely just break anyway due to the deformation caused by the bolt cropper jaws wedging themselves through the gap they've created by the tensile failure on the first side of the link. This can be done slowly and doesn't have to involve shocks. Sure, the actual moment that the metal's catastrophic failure begins, i.e. when the edges of the jaws start to accelerate toward each other, is a fast movement, but the failure on the first side of the link has already got beyond the point of no return at that stage. Hence, in a boltcropping attack, things happen relatively slowly, without significant shocks, until after it's already a done deal. I was not trying to sound rude but I was trying to dispell what I see as false science in this case. Apologies that it derailed this thread ;-)
Re Prince Rupert's Drop: Yes, these are spectacular and great fun. They were using tools to cut the 'tail' of the drop in the video, but you can actually do it very easily by snapping the tail by hand. It really unzips itself and the tail is where it starts. However, this is not what is happening with a chain link being cut with croppers. All you need to do is look at what is left afterwards: with the glass drop, the thing shatters into millions of pieces and totally unravels itself from the inside out because the extreme tension in the skin is suddenly released; with the chain link, it just breaks in one or two or sometimes three places. The fragments have broken surfaces you can look at and you can tell a lot about the steel from what you can see. Only really poor chains are likely to suffer from the brittle fracture on the 'other' side of the link; anything half-decent should need a second cut with the croppers. There should be enough ductility/toughness in the material to withstand the deformation caused by the cropper jaws cutting the first side. But once that first side has been cut, the whole link is then weaker so the second cut is easier as there is less reinforcement resisting the cropper jaws the second time around.
The "case hardening" vs. "through hardening" is also a simplification, as it happens. Pure case hardening leaves the core too soft and therefore still weak (so it won't resist the tensile load from croppers very well). Through hardening is also definitely bad as it can cause the brittleness right through that leads to snapping under hammer blows etc (and the double failure with croppers, albeit usually after a higher initial loading). The trick is really to get a balance so you have enough surface hardness through case hardening to stop hacksaws, but you also have controlled but modest hardening through the rest of the core. That gives you the tensile strength you also need. You can't get this balance right if you don't know what the steel is, and that's where most of the Chinese chains fail because the material varies all over the place. We do a lab test on every batch of our chains to check what we are producing, and the hardness profile across the cross-section is the key indicator for us.
The whole point of all this is to make a chain that is tough enough to stop the croppers etc getting through it at all, of course.
All interesting stuff, I think, but I've probably bored everyone to tears.
I hope that helps, and doesn't upset anyone this time :-)
I was trying to explain what actually happens, and the propagation of stress around the chain link, which will involve shockwaves :-) **after** the initial failure of one side of the chain link is missing the point.
The link has already been cut on one side and, as I tried to say before, it is a very good assumption that the other side of the link will fail. A decent chain will need a second cut to get through the other side of the link, and an over-brittle chain will likely just break anyway due to the deformation caused by the bolt cropper jaws wedging themselves through the gap they've created by the tensile failure on the first side of the link. This can be done slowly and doesn't have to involve shocks. Sure, the actual moment that the metal's catastrophic failure begins, i.e. when the edges of the jaws start to accelerate toward each other, is a fast movement, but the failure on the first side of the link has already got beyond the point of no return at that stage. Hence, in a boltcropping attack, things happen relatively slowly, without significant shocks, until after it's already a done deal. I was not trying to sound rude but I was trying to dispell what I see as false science in this case. Apologies that it derailed this thread ;-)
Re Prince Rupert's Drop: Yes, these are spectacular and great fun. They were using tools to cut the 'tail' of the drop in the video, but you can actually do it very easily by snapping the tail by hand. It really unzips itself and the tail is where it starts. However, this is not what is happening with a chain link being cut with croppers. All you need to do is look at what is left afterwards: with the glass drop, the thing shatters into millions of pieces and totally unravels itself from the inside out because the extreme tension in the skin is suddenly released; with the chain link, it just breaks in one or two or sometimes three places. The fragments have broken surfaces you can look at and you can tell a lot about the steel from what you can see. Only really poor chains are likely to suffer from the brittle fracture on the 'other' side of the link; anything half-decent should need a second cut with the croppers. There should be enough ductility/toughness in the material to withstand the deformation caused by the cropper jaws cutting the first side. But once that first side has been cut, the whole link is then weaker so the second cut is easier as there is less reinforcement resisting the cropper jaws the second time around.
The "case hardening" vs. "through hardening" is also a simplification, as it happens. Pure case hardening leaves the core too soft and therefore still weak (so it won't resist the tensile load from croppers very well). Through hardening is also definitely bad as it can cause the brittleness right through that leads to snapping under hammer blows etc (and the double failure with croppers, albeit usually after a higher initial loading). The trick is really to get a balance so you have enough surface hardness through case hardening to stop hacksaws, but you also have controlled but modest hardening through the rest of the core. That gives you the tensile strength you also need. You can't get this balance right if you don't know what the steel is, and that's where most of the Chinese chains fail because the material varies all over the place. We do a lab test on every batch of our chains to check what we are producing, and the hardness profile across the cross-section is the key indicator for us.
The whole point of all this is to make a chain that is tough enough to stop the croppers etc getting through it at all, of course.
All interesting stuff, I think, but I've probably bored everyone to tears.
I hope that helps, and doesn't upset anyone this time :-)
Whilst I appreciate the detail of how a chain fails and the physics etc, a chain is just a deterrent. My garage was broken into . . . a chap turned up with a petrol powered angle grinder, some massive bit of kit used for cutting up old houses and factories, took him a minute or two to cut two massive Chubb battleship padlocks off the garage and also the Almax chain on the bike and he tossed it on the back of his lorry and off he went. Gone in 5 mins and nothing would have stopped him.
Fortunately it was his bike and he'd illegally used my garage to store his bike whilst he worked on a flat I owned so it wasn't my bike but I still lost two padlocks. (He was a rouge builder who I am prosecuting)
If a thief really, really wants your bike, he will take it - a basic 16mm Almax chain with Squire padlock will deter the vast majority of thieves and I can't see the point of getting anything tougher . . . or am I wrong ?
Fortunately it was his bike and he'd illegally used my garage to store his bike whilst he worked on a flat I owned so it wasn't my bike but I still lost two padlocks. (He was a rouge builder who I am prosecuting)
If a thief really, really wants your bike, he will take it - a basic 16mm Almax chain with Squire padlock will deter the vast majority of thieves and I can't see the point of getting anything tougher . . . or am I wrong ?
Dog Star said:
If agree with your last point l, George.
If they have the gear with them to defeat that combination then it's game over.
At this point it goes down to other factors - noise for example.
If they are that determined, then they are possibly also the sort to use violence and, if unsuccessful on a first attempt, would be likely to come back with more tools at a later date.If they have the gear with them to defeat that combination then it's game over.
At this point it goes down to other factors - noise for example.
Pragma said:
The "case hardening" vs. "through hardening" is also a simplification, as it happens. Pure case hardening leaves the core too soft and therefore still weak (so it won't resist the tensile load from croppers very well). Through hardening is also definitely bad as it can cause the brittleness right through that leads to snapping under hammer blows etc (and the double failure with croppers, albeit usually after a higher initial loading). The trick is really to get a balance so you have enough surface hardness through case hardening to stop hacksaws, but you also have controlled but modest hardening through the rest of the core. That gives you the tensile strength you also need. You can't get this balance right if you don't know what the steel is, and that's where most of the Chinese chains fail because the material varies all over the place. We do a lab test on every batch of our chains to check what we are producing, and the hardness profile across the cross-section is the key indicator for us.
The whole point of all this is to make a chain that is tough enough to stop the croppers etc getting through it at all, of course.
All interesting stuff, I think, but I've probably bored everyone to tears.
I hope that helps, and doesn't upset anyone this time :-)
I think you are thinking too much The whole point of all this is to make a chain that is tough enough to stop the croppers etc getting through it at all, of course.
All interesting stuff, I think, but I've probably bored everyone to tears.
I hope that helps, and doesn't upset anyone this time :-)
As a guess, but an educated guess, the case hardened outside will have a yield strength of 800 or 1000MPa. The inside maybe 400MPa. 400MPa is still a lot, assuming a uniform tensile force and 1 sq cm core area, you would need to apply tensile force of 4 tonnes to reach the yield point. However the point is the core is ductile so it can withstand significant additional deformations after the yield point has been reached.
A feature of brittle material otoh is that crack size increases for no increase in applied load. That is not what you want in a security chain.
Oh the other thing is a gas axe will go through any security chain in seconds. Hydraulic cutters in not much more. A girder in minutes. So IMHO there is no point to ever increasing sizes of security chain beyond 16mm. If I was biking around some place where there are a lot of power tools around, like most developing countries, then I'd be inclined to use only a 13mm chain.
creampuff said:
Oh the other thing is a gas axe will go through any security chain in seconds. Hydraulic cutters in not much more. A girder in minutes. So IMHO there is no point to ever increasing sizes of security chain beyond 16mm. If I was biking around some place where there are a lot of power tools around, like most developing countries, then I'd be inclined to use only a 13mm chain.
I wouldn't... for the fact that 13mm is relatively easy to crop with croppers. While 16mm and up will require power tools.Once power tools get involved, it's game over anyway, but if you can deter hand croppers you're dettering a lot of the thieves.
creampuff said:
I think you are thinking too much
As a guess, but an educated guess, the case hardened outside will have a yield strength of 800 or 1000MPa. The inside maybe 400MPa. 400MPa is still a lot, assuming a uniform tensile force and 1 sq cm core area, you would need to apply tensile force of 4 tonnes to reach the yield point. However the point is the core is ductile so it can withstand significant additional deformations after the yield point has been reached.
A feature of brittle material otoh is that crack size increases for no increase in applied load. That is not what you want in a security chain.
Indeed. Brittleness is the killer and especially so because freezing & hammering attacks are very common and very quick and will exacerbate the brittleness, but you do still need strength because 42" croppers can exert about a 10 tonne load and you don't want them to get through, even after deformation.As a guess, but an educated guess, the case hardened outside will have a yield strength of 800 or 1000MPa. The inside maybe 400MPa. 400MPa is still a lot, assuming a uniform tensile force and 1 sq cm core area, you would need to apply tensile force of 4 tonnes to reach the yield point. However the point is the core is ductile so it can withstand significant additional deformations after the yield point has been reached.
A feature of brittle material otoh is that crack size increases for no increase in applied load. That is not what you want in a security chain.
It is harder to get a good result with smaller chains because you've got less material to work with, and you can't reduce the case thickness that much or hacksaws will get through it (and the core is much easier to cut, once you're through the case). There is therefore a higher percentage of the cross-section required in the case, and less available for the more ductile core. Hence, smaller chains are more vulnerable to hammering and to cropping attacks, but that's not really any surprise.
ZesPak said:
I wouldn't... for the fact that 13mm is relatively easy to crop with croppers. While 16mm and up will require power tools.
Once power tools get involved, it's game over anyway, but if you can deter hand croppers you're dettering a lot of the thieves.
Exactly. It's about percentages IMHO. By using a decent 16mm chain, you're probably reducing the numbers down to 1-2% of thieves that are capable and willing to take the risk to steal your bike. If it helps you to sleep at night to have a 19mm then that might drop the odds a little further and seems as far as is sensible to me. A 19mm is quite a lot more impressive than a 16mm and if that stops some thieves from trying, even if they would end up failing anyway, it has still reduced the chances that someone would cause damage to your bike in the attempt, so that adds to the justification for a 19mm but I think that is about as far as is sensible to go.Once power tools get involved, it's game over anyway, but if you can deter hand croppers you're dettering a lot of the thieves.
Stihl saws (petrol-powered grinders) will still likely get through even a 30mm chain, so it is down to other factors as DS said. The fact is that it is very rare that bikes are nicked with tools like that, or with gas, and even mains/battery grinders are very unusual. It does happen but insurance gives some protection to those sub-2% situations. A 16mm or 19mm chain hopefully means you do keep your stuff and reduces the chances of having to go through insurance claims and premiums going up even more. None of this stuff is infallible, but you don't want to let thieves have it easy so an appropriate deterrent is the way to go IMHO.
dunno who would have those stats....Police maybe?
perhaps if we dealt with the root cause of the issue we wouldnt need all this security...I mean why should we live in a society where we expect others to steal our belongings if we leave them unattended?
maybe the crime of motorcycle theft should be dealt with by a public beheading ? would that deter thieves maybe ?
...instead the Police have less and less resources to actually do anything about it, motorcyclists are a minority, no-one is harmed, so it seems to be left to the owner to figure out how to protect their property....
perhaps if we dealt with the root cause of the issue we wouldnt need all this security...I mean why should we live in a society where we expect others to steal our belongings if we leave them unattended?
maybe the crime of motorcycle theft should be dealt with by a public beheading ? would that deter thieves maybe ?
...instead the Police have less and less resources to actually do anything about it, motorcyclists are a minority, no-one is harmed, so it seems to be left to the owner to figure out how to protect their property....
Dog Star said:
This thread is depressing me 
Just out of interest I wonder just what ratio of bikes are stolen by croppers, grinders, hacksaws etc
I think I'll start a thread on this with a poll just to see.
The stats aren't that easy to come by, perhaps partly as it's not always obvious what technique/tool(s) were used, and it varies from area to area and gang to gang.Just out of interest I wonder just what ratio of bikes are stolen by croppers, grinders, hacksaws etc
I think I'll start a thread on this with a poll just to see.
As a very rough guess, I'd expect perhaps 80% of motorbikes are stolen with next to no tools as they've got no security to speak of: just an alarm, a disc lock, a cable lock (which is a contradiction in terms at this level, if you ask me), or a chain around nothing other than the bike. Then you're moving into the 42" cropper territory as that's the favourite of the more serious bike thieves that are coming in vans so carrying a heavy tool like that is no problem. I think all that lot does total over 95% of thefts, and the grinders & gas etc are the small minority (1-2% would be my guess). If the thieves are carrying the 42" croppers, then anything that can't stop them is very vulnerable.
I agree that the penalties for convicted thieves are not enough of a deterrent, and the people buying cheap parts off eBay and the manufacturers charging such ridiculous amounts for new parts are the other side of it. It's unlikely there will be a fundamental change in any aspect of this so all we can do is take reasonable precautions to protect our stuff and try to keep the odds heavily weighted in our favour.
ZesPak said:
Just to derail the thread completely, as an interested party, how would you pitch your products against similar ones provided by Almax?
What would be the USP's of either?
I don't want to get too 'salesey' as I will get complained at (again!), but to give you a straight answer, I honestly think there is nothing to choose between the chains. Their chains are equivalent to ours and our chains are equivalent to theirs in our opinion. I should have mentioned before about the hardness profile that we tested theirs and our lab results were within about 2% of theirs (i.e. they also have a mid-level hardness across the core, just as we do). We get about 2% variation from batch to batch and actually Almax and we have been using the same heat treatment company for years. I don't know what they are doing now, but we are both set apart from the competition that often does HT in China with dramatically variable quality as the outcome. We are both trying to produce a good result.What would be the USP's of either?
The choice comes down to whatever you prefer, and potentially what else we each offer.
We do the chains in longer lengths, up to 6m for the 16mm and 4m for the 19mm (they get too heavy beyond those lengths!). I think Almax max-out at 2.5m in both.
We use the same Squire SS65CS lock, but we are using a higher grade R1 restricted cylinder in it. I think Almax are thinking about switching to that. It is harder to pick, but that is rarely a real issue in this country (but more of a problem on the continent). We switched to it last year as we thought it was generally a superior cylinder, and especially to the Chinese variant Squire were using at the time!
We also offer the Untouchable lock, which makes a nice (and cheaper) partner for the 16mm chain and sometimes also as a disc lock (but note the previous comments about disc locks on their own having a very limited deterrent effect).
We make our own ground anchors, including the only removable one that has approvals, and we make the Pin, which is where this thread started ;-)
We also have a wider range of chain gauges, with 13mm and 11mm, too, but would generally discourage people with motorbikes from using anything less than 16mm unless it is a deliberate compromise for portability. And we make other stuff, as well.
You're welcome to e-mail us separately if you want more info, and there's lots on our web site.
I hope that helps, without annoying people!
LeadFarmer said:
I did get great service from Pragmasis, from advice over the phone to fast delivery of the pin. I now just need to install my ground anchor and I'll then be ordering a chain and lock.
Glad you're pleased. We try to help :-)I just welded up another 65 ground anchors and at the current rate, they won't last us long! It's a good thing we've moved most of the business into a unit and taken on another lad as, without the extra space & capacity, we'd be going even more nuts! We're increasing batch sizes and running them more frequently and still sometimes struggling to keep up let alone get ahead. The Pin is a case in point as we have to make it in so many different sizes so we're often out of stock of one size or another, even though we plan the batches according to the popularity. These are all definitely nice problems to have, though, so I'm not complaining and all business is much appreciated and thanks indeed :-)
Pragma, can your 19mm chains be made to a specified length, say 130cm? I'll be using the chain in conjunction with your pin and a ground anchor. Im not wanting my chain to have too much excess slack and rest on the floor. I guess my other option is to order a 150cm chain and then take it somewhere to cut a few excess links off?
graphene said:
ZesPak said:
creampuff said:
Oh the other thing is a gas axe will go through any security chain in seconds. Hydraulic cutters in not much more. A girder in minutes. So IMHO there is no point to ever increasing sizes of security chain beyond 16mm. If I was biking around some place where there are a lot of power tools around, like most developing countries, then I'd be inclined to use only a 13mm chain.
I wouldn't... for the fact that 13mm is relatively easy to crop with croppers. While 16mm and up will require power tools.Once power tools get involved, it's game over anyway, but if you can deter hand croppers you're dettering a lot of the thieves.
Just as an aside I saw one dude walking around Manila (Philippines) yesterday carrying a full size fridge on his back.
LeadFarmer said:
Pragma, can your 19mm chains be made to a specified length, say 130cm? I'll be using the chain in conjunction with your pin and a ground anchor. Im not wanting my chain to have too much excess slack and rest on the floor. I guess my other option is to order a 150cm chain and then take it somewhere to cut a few excess links off?
Yes, we can do custom lengths, although we have to be careful to avoid ending up with an 'offcut' that won't be sellable/cuttable into normal lengths. Something like a 1.3m, or other similarly short lengths, are normally OK. The bigger chains, especially, are expensive to make, so waste is bad for all of us. Happy to talk about it, but we wouldn't be happy to get a 1.3m length sent back if it's one link too short as we'd be unable to sell it to anyone else! I.e. we can do a lot of custom stuff to help out, but the responsibility is yours to ensure you are ordering the right thing ;-)Another option, of course, is to have a chain that is a little too long and to simply poke the Pin through link(s) away from the end. That way you have more versatility in the future if your needs change.
I hope that helps,
Steve.
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