I was thinking about this today as I walked out of work through the doors with the magnetic locks. You know the kind: a big electromagnet at the top of the door frame that sucks onto a metal plate on the door.
Could a determined person bash his way through?
The doors at work seem robust, but a little shaky, and all you need to do is break the grip a teensy bit. Anyone ever tried it?
[QUOTE=minor7flat5]
I was thinking about this today as I walked out of work through the doors with the magnetic locks. You know the kind: a big electromagnet at the top of the door frame that sucks onto a metal plate on the door.
Could a determined person bash his way through?
The doors at work seem robust, but a little shaky, and all you need to do is break the grip a teensy bit. Anyone ever tried it?
[/QUOTE]
Can’t give a quantitative answer but they are plenty strong. Had one in an apartment building I lived in and the steel door would break before the magnet would give. Believe me, they are secure.
A similar anecdote checking in - I saw a steel-clad door at a rehab facility that suffered structural failure when someone tried to force it off a mag latch, apparently by running full speed at it. The upper third or so of the door’s “skin” was peeled loose from the door’s core and the foolish human also failed structurally - they said he broke his shoulder and upper arm from the impact.
BTW - the latch held, and he didn’t get anywhere except to the ER with a police escort.
A little googling turns up that a common “strength” for these locks is 1200 pounds, and 1800 pounders are available. 1200 pounds isn’t well-defined though - I can only assume they mean that the magnet is capable of holding up a 1200 pound weight, or that someone would have to exert a force of 1201 pounds against a door to defeat the lock.
What happens if the power goes out?
The lock stops functioning. But that’s something a facilities planner needs to consider. Most places I’ve seen that use such locks are the kinds of places that have redundant commercial power sources such as telco central offices and large data centers.
In places that don’t have back-up power, you’d want the locks to quit working so that people can escape the building in an emergency.
[QUOTE=Patty O’Furniture]
The lock stops functioning. But that’s something a facilities planner needs to consider. Most places I’ve seen that use such locks are the kinds of places that have redundant commercial power sources such as telco central offices and large data centers.
In places that don’t have back-up power, you’d want the locks to quit working so that people can escape the building in an emergency.
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When I went to school at Texas A&M, all of the dorms had mag-locked doors, which from outside you unlocked by swiping your student ID, and from inside you could unlock either by triggering a motion sensor (by walking, or even waving, within a few feet of the door), or by slapping a big-ass button mounted next to the door.
If you held the door open too long without redoing one of three unlocking methods, two things would happen: 1) An obnoxious alarm would sound 2) 200 dormitory residents would scream, in unison, “SHUT THE ******* DOOR!”
Sometimes the motion sensors would stop working, and you’d get the hillarious image of a student running full tilt into an unyielding door. Great stuff to watch. 
And of course, in a power outage, or if the fire alarm was tripped, all of the exterior doors would unlock to allow students out and firefighters in (on a much cooler note, maglocks holding these big steel firedoors open in the halls would also release, causing the big doors to swing shut (you could just push them open, but it looked damn cool if you happened to be in the hall when an impromptu student-sponsored fire drill took place)
I really wish I had a point to this, but that’s my experience with the things.
[QUOTE=Darth Sensitive]
What happens if the power goes out?
[/QUOTE]
That depends. First, is the system designed to fail ‘safe’ or fail ‘secure’? If safe, then the locks would allow egress. If secure, then they must have a backup power source, either for the security system, or for the facility.
As far as the holding power of the locks, 1200 and 1800# are available from a number of security equipment manufacturers, as explained upthread.
[QUOTE=Raguleader]
When I went to school at Texas A&M, all of the dorms had mag-locked doors, which from outside you unlocked by swiping your student ID, and from inside you could unlock either by triggering a motion sensor (by walking, or even waving, within a few feet of the door), or by slapping a big-ass button mounted next to the door.
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What you’re describing, in terms of the motion sensor, is known as PIR request-to-exit (PIR being Passive Infrared). While those mag locks are certainly pretty strong, they can be defeated with the right counter-magnet in some cases; with any PIR request-to-exit system there are a lot of ways to defeat it. The cliched approach is to slide a mylar balloon under the door to trip the alarm.
Currently, the security model for darn near all areas of concern (physical, technical, and administrative) is for layered security. So your PIR for your mag locks should have a verification/rejection component. Most really don’t though.
[QUOTE=Raguleader]
When I went to school at Texas A&M, all of the dorms had mag-locked doors, which from outside you unlocked by swiping your student ID, and from inside you could unlock either by triggering a motion sensor (by walking, or even waving, within a few feet of the door), or by slapping a big-ass button mounted next to the door.
If you held the door open too long without redoing one of three unlocking methods, two things would happen: 1) An obnoxious alarm would sound 2) 200 dormitory residents would scream, in unison, “SHUT THE ******* DOOR!”
Sometimes the motion sensors would stop working, and you’d get the hillarious image of a student running full tilt into an unyielding door. Great stuff to watch.
And of course, in a power outage, or if the fire alarm was tripped, all of the exterior doors would unlock to allow students out and firefighters in (on a much cooler note, maglocks holding these big steel firedoors open in the halls would also release, causing the big doors to swing shut (you could just push them open, but it looked damn cool if you happened to be in the hall when an impromptu student-sponsored fire drill took place)
I really wish I had a point to this, but that’s my experience with the things.
[/QUOTE]
Heh… I remember that stuff. I was an RA in Lechner from 1992-1995, and set the fire alarms off myself twice. That was how you knew you’d set them off - the maglocks would disengage and the fire doors would all shut. You could hear them go off in sequence across the different floors. Wham, wham, wham, wham, wham.
Then I’d have to lie to my boss saying that I had no idea who’d set the alarm off, and that I’d keep an eye out for the perpetrators. (when in fact, I’d been lighting spray-can deodorant in the hallway with residents)
[QUOTE=gotpasswords]
A little googling turns up that a common “strength” for these locks is 1200 pounds, and 1800 pounders are available. 1200 pounds isn’t well-defined though - I can only assume they mean that the magnet is capable of holding up a 1200 pound weight, or that someone would have to exert a force of 1201 pounds against a door to defeat the lock.
[/QUOTE]
Note also that to achieve the rated strength, the maglock must be correctly aligned with the door. An incorrectly aligned lock will not hold as tightly.
[QUOTE=Darth Sensitive]
What happens if the power goes out?
[/QUOTE]
I was just working on integrating a remote-control system with a door-lock system. This system had a small gel-cell battery that was good for two hours.
[QUOTE=Gorsnak]
Note also that to achieve the rated strength, the maglock must be correctly aligned with the door. An incorrectly aligned lock will not hold as tightly.
[/QUOTE]
See, that’s the kind of stuff I’m looking for. Real in-the-field strength instead of specs from the manufacturer.
As I said, the door at work, unchanged for at the last 17 years I have been employed there, is heavily used, and it seems to me that a solid blow to the bottom corner might just have enough leverage to break the magnet’s grip. 1200lbs in perfect conditions sounds like it would be quite defeatable in a shaky door with a grubby magnet.
Of course, the door at work is right in front of the security office, and they are looking straight at you as you walk through, so it wouldn’t really go unnoticed.
When I lost my security card for my college magnetic door lock I would slip a piece of paper over the mag lock when I wanted to go to the bathroom or otherwise pop out for a minute or two. It made the door work like any normal door.
[QUOTE=An Gadaí]
When I lost my security card for my college magnetic door lock I would slip a piece of paper over the mag lock when I wanted to go to the bathroom or otherwise pop out for a minute or two. It made the door work like any normal door.
[/QUOTE]
Is this a woosh? Paper doesn’t affect magnetic fields.
[QUOTE=bump]
Heh… I remember that stuff. I was an RA in Lechner from 1992-1995, and set the fire alarms off myself twice. That was how you knew you’d set them off - the maglocks would disengage and the fire doors would all shut. You could hear them go off in sequence across the different floors. Wham, wham, wham, wham, wham.
Then I’d have to lie to my boss saying that I had no idea who’d set the alarm off, and that I’d keep an eye out for the perpetrators. (when in fact, I’d been lighting spray-can deodorant in the hallway with residents)
[/QUOTE]
Heh, there are times I really wish I lived in the Nerd Dorm instead of in Moore Hall, but then to do that, I’d have to be maintaining at least a passing GPR, right?
So the doors slam in sequence? That’s cool. It’d be cooler if they slid down from the ceiling, like in Star Trek II and VI. 
I remember one night, in Moore Hall (Bleed Maroon Forever 
), the fire alarm went off at 6PM, 8PM, 10PM and 2AM. I was ready to kill someone. On a related note, I always felt sorry for the girls living in DG, who usually had to walk past either the Moore Hall Benchfucks or the Moses Hall Benchfucks (We all got memos from Reslife about sexual harassment because of those fine upstanding gentleman, and those same gentlemen got a rock thrown through my window once because my dorm room was right behind their benches and someone had a lousy throwing arm).
I think one of the doors in my dorm wasn’t aligned correctly, or the lock was wearing out, or something. One day, the IR door unlocker thingy wasn’t working, and I was pissed about my bike going missing, and when the door wouldn’t open for me, I gave it a good solid kick to the crash bar. Thing popped right open.
[QUOTE=Santo Rugger]
Is this a woosh? Paper doesn’t affect magnetic fields.
[/QUOTE]
If the paper was thick enough, it could put enough distance between the magnets to prevent a seal, though I’d imagine you’d need to fold the paper up a bit to make that happen.
No woosh (whoosh?), standard A4 sheet for photocopying, folded over the top of the door where the mag lock is located.
[QUOTE=Raguleader]
I think one of the doors in my dorm wasn’t aligned correctly, or the lock was wearing out, or something. One day, the IR door unlocker thingy wasn’t working, and I was pissed about my bike going missing, and when the door wouldn’t open for me, I gave it a good solid kick to the crash bar. Thing popped right open.
[/QUOTE]
I’m guessing that it’s some sort of function of distance between the magnet(s) and whatever they’re attaching to, as well as some kind of surface area issue going on, so that if it’s not aligned well, or the door gets warped somehow, the holding force is greatly lessened.
BTW, did you know Schumacher’s co-ed now? No more Sammy the Seaman.(mascot that looked like either a sperm cell or large comma wearing a sailor hat)
Whoever monitors the door alarms would certainly notice, too. It might be an off-site vendor like ADT. A door opened without the controller’s permission (using a key or defeating the magnet somehow) would cause a “forced door” alert to be raised at the monitoring center.