Diagnose This Hotel's Access Problem

A member sent this problem in:

"I stayed at a hotel a couple weeks ago and the meeting room we used had a card access mag lock on the entrance doors to the room. The problem was it couldn't prevent anyone from entering if they wanted to. I just jerked the doors open easily."

He sent this video:

After watching it, vote on what you think is the root cause of the problem.

Needs one seperate maglock on each door, (or a double deal)?

To everyone:

I'll restate the issue if you didn't catch it:

The doors can be jerked open even when they should be locked/secured.

The answer is quite obvious from the video.

The answer is quite obvious from the video.

Not if you have your sound down :(

Without having sound up... I'd have to go with U1's initial diagnosis: looks like a single-door lock, which means each door's plate is only getting a weak bond, just enough to offer a token resistance.

Looks like the maglock armature plate is not making proper/full contact with the mag lock. Could be caused by misaligned door or an obstruction of some sort applied to the maglock - IE - dirt build up or similar.

Could also be a failing power supply not giving enough voltage/current needed for the full holding force which judging by the size of the lock in the video should be around 1500Lbs.

Definitely the wrong lock for these types of doors! Armature plate not making contact properly (needs to be one per door). Should be a twin like this:

Twin mag

It seems to be single door maglock being used for a double door.

Ops, I should have watched the video (ha-ha)!

So good comments everyone! Starting with Und1's answer up top, I agree the most obvious problem is the maglock being used is meant for securing one door, not two.

Here is a results snapshot showing about half of total votes concur:

Simply stated, a magnet is only as strong as the bond it creates. In order to create the strongest bond, the armature (also called strike by some) must be in full contact with the magnet.

Downrated Bond Force

In the case of the door above, it looks like the armature was cut into two pieces, one for each door, but done in such a way that each armature only contacts ~40% of the magnet surface.

This means that the individual bond strength of just that door is downrated significantly. If that particular magnet is rated at 500 pounds of bond force, 40% of that rating is 200 pounds.

This means that each door is only being held secure by a fraction of the designed rating of the maglock. The OP is able to yank a modest amount and break the bond by hand. Not good!

There are other factors at play here: for example, the way the magnetic field propagates assumes the armature is a solid piece. Cutting it in two introduces an air gap (between the doors) that acts as a dielectric essentially weakening the max possible bond.

Door Leverage

Also consider those conference room doors are quite tall. The fact a user can grab the door handle and essentially use leverage over about 4' - 5' of the leaf to pry the lock apart is another reason to use strong locks, especially in this application. Just image if a user jammed a crowbar of the same length between the armature and magnet. Popping it off wouldn't be difficult for a weak magnet!

When specifying maglocks, the height of the door needs to be factored into the bond rating. If the door is taller than 8', taller doors need stronger locks.

This is where frame features like mullions and door hardware with strike latches can improve door security. Beyond just a latch alone, they make the door more rigid and harder to flex.

Better Maglock Solutions

Now, there are examples of 'split armature' maglocks, but it should be noted those units are designed with high bond, individual coils and armatures to mitigate exactly this sort of weakening, or they disclaim the resulting weakness. (Another one) These beefed-up units tend to be expensive, in many cases 3X the cost of a basic single armature model.

It is much more common to use two single maglocks, or dual maglock units like many of you have mentioned.

This is really benefitial to me. Can we have more of this in the future? I would really appreciated it.

Yes, we'll have another 'Diagnose This' access problem next week.

If any members see or have questions that would make a good problem like this, then please email us! I'd be happy to help frame it as a good puzzle/post.

Is the card reader broken as well?

It does not appear that way. What would make you think that?

Just that a 3 or 4 second unlock time seems a little quick for an reader that is on an adjacent wall and that would often be used by people unfamiliar (hotel guests) with its operation.

Add to that the fact that it opens into a conference room, means that it could be used by staff, frequently with both doors open, for equipment delivery and housekeeping.

Getting both doors open in that short a span, for say a water cart, might prove challenging.

But it might be set to lock that quickly; and it wouldn't be surprising, given the rest of the install.

Though I am unable to hear the sound of the armature automatically relocking in any event, maybe it's too quiet?

And I though I agree with your assessment about the reduced locking force, maybe there is a misalignment as well, since it doesn't even appear like 200lbs of locking force, but I'm just guessing on that.

Finally, why does he swipe anyway, he could just have gone to the door at once, no?

Also, the reader does not show a green light, (I'm not sure if they always do though), and it sounds like he says "idiots" after the second swipe.

So maybe it's just a bad credential? (In addition to the inadequate hardware, of course).