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Magnetic lock-pins

To make lock-bumping harder
  [vote for,

Conventional cylinder locks can be picked in moments, even by an amateur, using a bump-key (aka pick gun, bump gun etc).

(Skip this para if you're familiar with locks.) In a regular lock, there are a series of pins that run through the body of the lock and through the cylinder (the part that turns). Each pin has a split (gap) in it at a different height. The key just lifts all the pins to the right height, so their splits are flush with the edge of the cylinder, which can then be turned. The pins are pushed downward with little springs, against which the key acts to lift the pins.

(Skip this para if you know about bumping.) A bump-key or pick gun is just a thin metal rod that slides into the keyway, and a mechanism for giving the rod a small but very sharp upward tap. This tap bounces the pins upward, and it's the top half of each pin that bounces the most. As a result, there's a fraction of a second where the top halves of all the pins are all the way up, and the bottom halves are all low. During this fraction of a second, the lock can turn.

(Welcome back.) Bumping would be much harder if the movement of the pins were damped - it basically wouldn't work. You can do this by putting heavy oil into the lock (it will still work fine with a key), but then you get an oily key each time you use it.


Instead of oil, just make the *top* half of each pin strongly magnetic. You can already get tiny cylindrical rare-earth magnets, so this would be no problem. The lock body is normally brass or zinc - non-magnetic metals. As a result, the movement of the *top* halves of the pins will be heavily damped by magnetic induction (just like the experiment of dropping a strong magnet down a copper pipe). The resisting force will be greatest when the velocity is highest, meaning that the "bumped" pins will only travel a very short distance.

So, this is a very simple-to-implement change that would make locks resistant to bumping, whilst leaving them just as convenient to use.

MaxwellBuchanan, May 29 2019

https://pin.it/3dyqvgctaa6hya Max's pride - now on Gumtree [xenzag, May 31 2019]


       I am not convinced this would have the desired effect. The eddy currents are only induced when the magnet is moving, so at the point of the initial bump there will be no resistance. Oil on the other hand has stiction and surface tension, in addition to the v^2 damping effect.   

       But I may be wrong, and it would be quite simple to try this out.
mitxela, May 29 2019

       Oh, and another thing: would this not make it trivial to unlock, using a master key made of magnets that repel the pins?
mitxela, May 29 2019

       If the tops and bottoms were both magnets then they would stick together and so the bump would not separate them
pocmloc, May 29 2019

       //at the point of the initial bump there will be no resistance// Yes, but as soon as the bump starts, resistance will be very high.   

       //using a master key made of magnets that repel the pins// Hmm. Possible. But you'd have to overcome the spring force, which is fairly high. Also, you could randomize the polarity of the pins, necessitating 32 different master keys for a 5-pin lock.   

       //If the tops and bottoms were both magnets// Also possible.
MaxwellBuchanan, May 29 2019

       How does a bump, produce momentum in more than one direction at once?
wjt, May 30 2019

       It works a bit like Newton's Cradle, where the impact of one ball is transmitted through the intermediate ones, and only the ball at the opposite end is sent swinging. Likewise, when you hit the end of the inner part of the pin, it stays more-or- less still and only the top part flies upward.
MaxwellBuchanan, May 30 2019

       I think this would be secure right up to the point where burglars realised they could lift the upper pins with a strong magnet.
Loris, May 30 2019

       I don't think that would work. The magnet would need to be held against the front of the door, above the lock, and would be pulling the pins at an angle; I think they'd just stick.   

       (I have actually used a magnet to break into my own house, but in a rather different way.)
MaxwellBuchanan, May 30 2019

       You hit the window with the magnet?   

       If you din't actually break anything then technically it doesn't count as breaking in, I would of thaught.
pocmloc, May 30 2019

       No, I used the magnet to open a window latch. It was a wrought iron latch, and a stupidly strong rare-earth magnet. The same magnet, some months later, attacked my laptop and physically bent the read-head in its hard drive.
MaxwellBuchanan, May 30 2019

       You can use strong magnets to open most standard key locks.   

       Locks really only keep out honest people.   

       Some, not most. What you're doing with the magnet is actually bypassing the lock (ie, releasing a lever that holds the bolt, and which can normally only be actuated by turning the lock), and it only works on certain deadbolt locks. At least here in the UK, locks that you can bypass that way are not the norm.
MaxwellBuchanan, May 30 2019

       This won't prevent locks being picked. When you pick a lock, you insert a flat piece of metal that puts torsion on all of the pins, causing them to bind against the sides of the shafts in which they slide. The pick then forces them to lock into the correct position one by one. No magnet is ever going to be powerful enough to interfere with this relentless process. Picking the average lock is easy. Picking 'this' lock will be just as easy. Sorry Max, but if this is your lock, I'll be in your house within 2 minutes, then out again with your prized collection of decorative crocheted pink toilet roll covers and matching ties.
xenzag, May 30 2019

       Uh, [xen], mon amie, can I suggest you read the actual idea? This is not intended as a means to prevent picking. It is intended as a means to prevent bumping.   

       Picking requires considerable skill, even for a regular 5-pin Yale lock (which has at least two spool-pins to make picking harder). Bumping requires a knack (if using a manual bump- key), or almost no skill at all (if using an electric bump- key).   

       Most burglaries happen through unlocked doors or windows, stolen keys or by simply breaking something. A minority happen through lock bumping. Very, very few happen through actual lock picking, because why bother?   

       You're very welcome to come and try to pick any of my door locks. They are regular Yales, except I put spool-pins at *all* the positions when I re-keyed them. I should also mention that unless you're a _very_ good sprinter, 2 minutes won't even get you beyond the front hallway.
MaxwellBuchanan, May 31 2019

       I've already been and gone! Check on Gumtree (pic in link) Yale locks are a breeze.
xenzag, May 31 2019

       I hadn't heard of spool pins before, so I Googled.
I weep for humanity.
Virtually every search result was about lock picking and how to BEAT spool pins. It's a sad indictment on the society we have become...
neutrinos_shadow, May 31 2019

       Society hasn't changed, locks only keep out honest people.
Honest people don't need locks.
Honest people don't need laws.

       Honest people are WAY outnumbered... and majority rules.   

       I like it.   

       Will it change the feel of inserting the key?   

       Perhaps chipkeys for houses will be the next big thing.   

       But as a Russian guy once said, "Maybe the lock makes it a two-kick door instead of a one-kick door."
sninctown, May 31 2019

       //Honest people don't need laws.//   

       For some purposes, even honest people need laws. For example, it's not self-evidently more honest to drive on one side of the road than the other. Laws save people from having to renegotiate things like this on a case-by-case basis.
pertinax, May 31 2019

       The pins just need to be at different angles to each other. Picking would be more difficult.   

       Picking is helped by the lower pin dropping. Magnetism would stop this by putting weight on the top pin when the pick moves on.The set also might be more difficult to find.
wjt, May 31 2019

       //even honest people need laws.//   

       Fair point about driving. Okay I guess some rules are in order.   


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