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Grinder-Proof Bike Lock

Use the hierarchy of materials to beat thieving toerags.
  [vote for,

The typical bike lock is not the most sophisticated device. Typically, they're a U-shape or chain made of ~10mm steel, hardened if you spent wisely. Most commonly these are defeated by cutting right through them with a cordless angle grinder and a cut-off wheel. Such things are fantastically efficient because they're made of materials harder than steel.

Materials harder than steel are one of the things that make steel so popular, with silicon/tungsten carbide you can slice right through steel and make it any shape you like, all it takes is horsepower.

If you want to slice through things ending in "carbide" things get tricky. Diamond and cubic boron nitride will do it, but not at all quickly or easily compared to steel. So can we make a bike lock out of tungsten carbide? Well, yes. But then you could smash it with a hammer.

So. Take your favorite bike lock shape. Make it tubular, rather than solid. Fill the tube with an epoxy resin mixed with big/small chunks of carbide and some steel powder and you're done.

The tube shouldn't be anymore vulnerable to forcing with hydraulics. Cutting with a normal wheel will get through the steel and then bog down* in the carbide epoxy mix. Even a diamond saw will have trouble, since the hard carbide is somewhat flexibly mounted in the epoxy, leading to a juddering cut, plus, the steel casing is still in place, and hot diamond dissolves in hot steel.

As a side bonus, the lock should be a good bit lighter.

* dangerously, with any luck. Hopefully, the disk cuts quickly through a section of epoxy and suddenly catches on a chunk of carbide. This would shock-load the fragile disk and shattering may occur. A shattered cut off disk is often dangerous, but proper PPE will protect the prudent thief.

bs0u0155, Mar 09 2020

Chobham armour https://en.wikipedi...wiki/Chobham_armour
" ... composed of ceramic tiles encased within a metal framework ...". We could tell you more, but then we'd have to kill you. [8th of 7, Mar 09 2020]

Altor SAF http://altorsaflock.com/
Advertised as resisting angle grinders... [Chairborne Hero, Mar 09 2020]

Booby traps https://definitions....com/b/booby-traps/
What kind of "civilization" outlaws exploding bike locks? [Chairborne Hero, Mar 10 2020]

https://www.indiego...r-proof-bike-lock#/ [xenzag, Mar 12 2020]

Rapid Bike Theft Device https://explosives....oduct/rebar-cutter/
[bs0u0155, Mar 16 2020]


       You're describing ceramic vehicle armour - Chobham armour <link> - which is Baked and WKTE.
8th of 7, Mar 09 2020

       Best advice I ever got was to park your bike next to a more expensive one.
pocmloc, Mar 09 2020

       // Chobham & other reactive armor.   

       Nifty but not baked into bike locks, as far as I know. 8th, have you got a product listing for one?   

       // park next to a more expensive bike   

       Or ride something too challenging for the casual thief to ride off with. Fixie, recumbent, folder. The last can be very safe as you really don't need to lock it up anywhere - just keep it with you.   

       This is the main reason I turned down 8th's kind offer to buy me a Buddnitz Model Ø (or even a Model 1). I'd almost submit to assimilation to have one - but it'd be impossible to secure it anywhere. Not even in the garage next to my fixie, recumbent, or folder.
Chairborne Hero, Mar 09 2020

       The Altor SAF (link) is advertised as grinder-proof. And it defeats them pretty much as suggested here - by wearing out or breaking the grinder's blade.   

       But it's really heavy, and does not use reactive armour or even a complex mix of materials.
Chairborne Hero, Mar 09 2020

       Looking at the Altor SAF link, it occurs to me that for this approach to succeed you're also going to need grinder-proof bike-racks.
Loris, Mar 09 2020

       // does not use reactive armor //   

       Sp. "armour"   

       We call that "underspecified".
8th of 7, Mar 09 2020

       // armor vs armour //   

       Fixed, for now. I might change it back though, have to check my calendar to see if I should spelling as an American or a Brit this week.   

       // you're also going to need grinder-proof bike-racks. //   

       It is just so. Bicycling Magazine reviewed the lock, acknowledged it *did* take them over an hour to cut through using a 5" wheel - and that cutting through what the bike was locked up TO would be easier. Or even cutting the bike frame itself if all they were after was high-end parts.   

       They also suggested that a 7" wheel might make short work of the lock...
Chairborne Hero, Mar 09 2020

       //Best advice I ever got was to park your bike next to a more expensive one// - indeed! I also lock my bike* with a lock which cost more than the bike

* my commuting bike, not my nice bike or my second-best bike
hippo, Mar 09 2020

       When you get your commuting bike on Freecycle like I did, that's not hard. I did have to buy new tyres for it though.
pocmloc, Mar 09 2020

       Also, I’m not sure this idea would prevent the car-jack method of breaking u-locks
hippo, Mar 09 2020

       A red-on-yellow cardboard tag with the biohazard symbol and the text "CORONAVIRUS - AWAITING DECONTAMINATION" in several languages should be at least as good as a lock - at the moment ...
8th of 7, Mar 09 2020

       //Altor SAF// LOOK AT THE SIZE OF THE THING! it's just a normal lock in a thick aluminum case.
bs0u0155, Mar 10 2020

       I wuz thinking about a very cheap, tubular lock filled with some substance guaranteed to explode when in contact with air. One might, perhaps, applaud* when the thief cuts through it.   

       [+] for your idea.   

       * while wearing protective clothing, from a safe distance.
whatrock, Mar 10 2020

       Unfortunately, such booby traps are illegal (link). Can ya believe that?
Chairborne Hero, Mar 10 2020

       To act or not to act, that is the question. Whether tis nobler in the mind to suffer the grinders and maliciousness of such vermin, or to bake a simple idea and blow them all away? For surely, ruffians know they misbehave and should reap what they soweth.   

       Halmet, Act 3
whatrock, Mar 10 2020

       Love this!
21 Quest, Mar 12 2020

       See last link. This thing is totally bonkers.
xenzag, Mar 12 2020

       [xenzag] that "totally bonkers" thing is the same product I posted a few days ago - Altor SAF.
Chairborne Hero, Mar 12 2020

       Ha - funny. Didn't notice it. Will delete or fight you for it!
xenzag, Mar 12 2020

       That's what you get for not reading through to the end. Leave it up, their Indiegogo video has lots of pretty sparks.
Chairborne Hero, Mar 12 2020

       Thermite... white phosphorus... large amounts of unstable stuff that goes 'bang!' and scatters courage and various body parts...   

       Yes, the Help file. I know, guv. Off I go. (plods off to revisit the Help file, yet again)
whatrock, Mar 12 2020

       Perhaps the traditional U-shaped design could be upgraded with a series of free spinning beads slipped over the U. Hard to angle grind someothat keeps rotating. The thief could angle their grinder (heh) 90 degrees but that makes their task much more difficult and slower.
AusCan531, Mar 12 2020

       I see no-one's touched the grindr-proof bike lock. Probably just as well.
pertinax, Mar 16 2020

       //a series of free spinning beads slipped over the U//   

       Could work, and carbide beads are simple enough to make, although getting them tight enough that you can't get the disk between them could be tricky.
bs0u0155, Mar 16 2020

       Make them asymmetric, with a spigot/undercut, then each bead under/overlaps its neighbour.   

       The ends of the sequence are problematic but could be protected with a thick outer sleeve over the beads.   

       Not sure how well that would protect against having det cord wound round the "U" and then initiated.
8th of 7, Mar 16 2020

       //Not sure how well that would protect against having det cord//   

       Was about to write an idea for an explosive faster-than-key bike lock unlocker. But, a quick google suggests someone already made one <link>. The good thing about using explosives to steal bikes in public areas, is that the actual bike stealing will likely be a minor component of the legal ramifications.
bs0u0155, Mar 16 2020

       That kind of depends on the neighborhood...
8th of 7, Mar 16 2020

       //depends on the neighborhood...//   

       True, in the rougher neighborhoods of Philly it would blend in with the general gunfire. Conversely, over the river in Camden, extensive firearms experience is so common that you'd actually draw a small crowd. That's the sort of place it is. I mean, many people think the Iowa class battleship parked on the Delaware is retired. Oh no, that's just the sort of thing you need if you get into a serious disagreement with the population of Camden.
bs0u0155, Mar 16 2020


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