a technical query about plug spinners

[C locked]

Has anyone ever measured the force a plug spinner "Spins" at?

[Raymond]

A really good question. And.. For a relatively strong spring above the top pin, what speed must you achieve before the centrifugal force and resulting increase in the friction of the bottom pin against the wall of the lock allows it to slip past the top pin without catching? Any mechanical engineering genius's want to try to anaylize this?

[spoonzor]

Sorry I can't give you an answer but I do know most plug spinners can be wound/set at different speeds/force. So there doesn't seem to be one set speed that "just works" that they all use.

Since i'm just a hobbyist I never really used one (yet). If a lock doesn't open one way, just pick it again the other way, twice the fun..
I did see a friend of mine break some locks with a plug spinner because he wound it to tight/spinned it to fast, guess you have to find the balance yourself.

Would be interested in an engineering point of view on this, but am afraid different locks have different tolerances and different friction levels on the cylinder.

[Raymond]

Commercially I dont have time just pick the lock the other way. The plug spinners really pay for them selves after a few uses. Some doors have the wall so close that I dont fit comfortably into the space allowed. I have to pick it the wrong way and then spin it open. Ever notice as you build your habbits that picking is very difficult using your opposite hand. Plug spinners are a wonderful tool. I've made two, bought one, and carry all three in my truck.

[spoonzor]

Did you ever break a lock with a plug spinner?
Did you ever failed to spin a lock with a plug spinner?

[C locked]

How can a plug spinner break the lock. Surely it cannot exert more force then a key used forcefully.

[GWiens2001]

A clavicle can take about 30-35 pounds of force before breaking. But a sharp, fast impact can snap it at under 15 pounds.

The plug spinner, if strong, will exert sharp, fast pressure. Hopefully it is fast enough to not allow the driver pins to drop a all. If it does allow them to fall, at the least, the driver pin can (not will, but can) be deformed. That can cause binding in the pin channel, hense breaking the lock. Used properly, the plug spinner will most likely not cause damage. But it can.

Gordon

[xylac]

TL:DR; Are cheap locks harder to spin, and what really goes on when you spin a lock?

From a physics point of view, I suppose what matters is the speed (technically angular velocity) of the plug as the pin stacks line up again. Ignoring mass, this speed depends linearly on how far you twist the spinner in advance.

There's a small window where the keyway is vertical when the driver pins can drop down into the plug. If the driver pins only fall a little bit, the plug can wedge itself under them and continue spinning (think cutting tolerance of a key-- there's some error allowed in the depth of each cut).

That makes the necessary speed w_thresh a function of the vertical tolerance tol_v, the horizontal tolerance tol_h, and the spring strength k.
Roughly,
w_thresh ~ tol_h * sqrt(k/tol_v)

Assuming the two tolerances are related linearly, that gives w_thresh is proportional to the square root of the tolerance, so if you quadruple the tolerance, you double how far you heed to turn the spinner. This suggests that lower quality locks actually have to be spun at a higher speed than high quality locks. In itself that's an interesting result.

The model also shows that a stronger spring will make it more difficult to spin the plug. Could plug spinning be mitigated by using really strong springs?

And.. For a relatively strong spring above the top pin, what speed must you achieve before the centrifugal force and resulting increase in the friction of the bottom pin against the wall of the lock allows it to slip past the top pin without catching?

This makes me wonder what's really going on during the plug spinning. Is the plug spinning so fast the driver pins don't have a chance to drop? Or is the cetrifugal (yes, centrifugal http://xkcd.com/123/) force of the pins pushing up against the drivers preventing them from dropping down? Can you spin a plug too fast, such that the key pins fly up into the chambers and block rotation?

This is all just theory, so I'd like to hear more about what it's like in practice. Are cheaper locks harder to spin? Is overspinning a lock ever an issue? I know this doesn't answer the original question, but the physics of it turns out to be pretty interesting. I tried to keep the jargon to a minimum, but if anyone wants me to give more details I can.

[Altashot]

You explained it very well xylac!
This is exactly how I think of it.
Upon spinning the plug rapidly the weight of the bottom pins force them upward into their chambers against the housing. When the critical alignment occurs, hopefully the bottom pins will have acquired enough momentum to cancel out the spring force and skip passed the shear line.
Following this logic, then, it is possible to apply too much force where the bottom pins would acquire too much momentum and not only cancel out the springs, but overcome them, sending the bottom pins passed the shear line and into the bible.
Physics are Physics.

To attempt an answer to the OP, I played with an HPC spinner years ago, i never got the hang of it.
I got it to skip across the shear line but then it would bounce back and lock up again.
While experimenting with it, I tried to wind it to where it catches or "cocks" by twisting the blade with my fingers...I couldn't do it. I used pliers and got it to it's "cocked" position but I still took some good grip.

I never measured the actual force but my "guesstimate" would be 35 pounds of torque to reach 90 degrees, or 9 o'clock. I would also think that a softer spring wound to about 7 o'clock, just so that, it can complete it's arc at 5 o'clock and not bounce back any earlier than 2 o'clock would be better.

M.

[Raymond]

Maybe I just did not understand the explanation, but, I have never had the plug "bounce back" and relock. When I did not use enough winding, it would occasionally lock up at the normal shear line. If I used excessive winding the plug just went around until the action of the bolt stopped it. The plug spinner blade might twist a bit. I have always put the blade of the spinner as near the center of the plug as possible. I also turn the plug away from the opening direction, not near the shear, as I presumed this would allow it to build up some momentum and overcome the frictional resistance. If the plug would not turn smoothly to begin with, add some wet lubrication and try to loosen it.

Consider also that when the lock is picked, the bottom pins will probably not be at the shear line. They will probably be at the bottom of the holes and near the center axis of the plug. Close to the center there will not be much centripital force trying to move them outward. As mentioned earlier, the action you are looking for is to finess the plug holes past the spring loaded top pins before they can move. There is no force binding or in any way holding them up other than inertia. Your only hope is to increase the rotational speed to pass the top pins before they can move.

With my design theory as I hinted at above, I prefer a plug spinner with a long blade. I think that the longer blade will flex when the spinner stops and not create such a high shear force in a small length of blade. A thick heavy blade stopping very quickly when the plug stops could conceivable damage the keyway just the same as twisting a screwdriver in the keyway could.

I have never seen a lock broken by a plug spinner. However, I can conceive of one breaking if the plug and/or housing is made of plastic. It might also damage the dust cover like on auto locks if the blade is in contact only with the dust cover and not deeper into the actual keyway of the lock.

[C locked]

Thanks for your input raymond. I concede that a thick blade could damage like a screwdriver. Especially on automotive lock cylinders. Die cast swiss cheese...the cost of a manufacture to price society

[Achyfellow]

If someone has a youtube account you could send a PM to the slomoguys, maybe they can record a lock being plug spinned so we can see what is happening (If I recall correctly one company did this to see how bumping worked because apparently their anti-bump systems were based on a misconception about what was happening inside the lock)

[YouLuckyFox]

If someone has a youtube account you could send a PM to the slomoguys, maybe they can record a lock being plug spinned so we can see what is happening (If I recall correctly one company did this to see how bumping worked because apparently their anti-bump systems were based on a misconception about what was happening inside the lock)

That was Masterlock. There's a topic on it here.

[Achyfellow]

If someone has a youtube account you could send a PM to the slomoguys, maybe they can record a lock being plug spinned so we can see what is happening (If I recall correctly one company did this to see how bumping worked because apparently their anti-bump systems were based on a misconception about what was happening inside the lock)

That was Masterlock. There's a topic on it here.

Hey thanks a lot, I'll look it up. All I remembered was Schuyler talking about it at defcon years ago and I couldn't recall the company who did that

[C locked]

Have checked. I still have no way to measure the force. ...however. How a plug spinner works. It is just the plug spins faster then the pressure of the springs pushing down push the drivers. I tried a single chamber. With no bottom pin. Just spring and driver. ...no bottom pin to exert a centrifugal force. So it has to be that the spinning force is faster then the spring pressure.