Making an electric pick gun.


I have been making components for the test rig, but it occurred to me that it might have been a smarter move to make up an electric pick gun first, to see what problems exist. I have two of the solenoids rewound for 12 volts DC now, so I may as well use one of those to make a simple swinging arm type pick gun. The first version will be a single shot equivalent of the mechanical pick gun, except instead of a lever type snapping 'trigger' I will be using a micro switch to activate it.

Today I built the basic mechanism, which is simply a spring loaded solenoid, with an adjustable stroke length modification.

Actual size.

It is the same solenoid I showed you earlier, that I have rewound for 12 volts DC. The silver fork like object is the moveable core of the solenoid and when the solenoid is actuated the core moves sharply into the coil former. The spring returns the core, when the solenoid is switched off. The maximum length of travel is about 10.00mm. I drilled and tapped the core to take a 5mm threaded rod, which you can see protruding from the left hand end of the solenoid. The knurled steel knob adjusts the length of stroke  of the core, between zero and 10.00mm. In operation, the core, the 5mm steel rod and the knurled adjustment knob all move together as one assembly ........ in and out..

The electrical side is simply a micro switch in series with the solenoid and the battery. Press the switch and the solenoid actuates, let go of the switch and the solenoid de-activates. At a later date, the switch can be replaced by a micro-controller that can be programmed to give a variable pulse rate, which is also pulse width modulated. This approach also lends itself for linear raking and my 'one shot' investigation, although a swinging needle will be used on the first one.


11th February 2010.

Made up the swinging arm and front pivot. When 12 volts is connected to the solenoid the core is attracted into the body of the solenoid, compressing the return spring and pulling the right hand end of the swinging arm down. The far left hand end of the swinging arm swings upwards. The pick needle will be attached to the left hand end of the arm. It was a design requirement, that in operation the acceleration at the needle attachment point had to exceed one G, to make sure that the acceleration on any part of the needle exceeds 1 G. when the supply voltage is removed the solenoid de-energises, swinging the right hand end of the arm up, under the influence of the return spring, thus causing the left hand end of the arm to swing down. The knurled knob adjusts the maximum deflection of the arm and thus the amount of energy applied during the strike.

So what is it all about ?.  Bump keys and pick guns work in accordance with Newton's Third Law of Motion .... for every action , there is an equal and opposite reaction. At first glance it may be difficult to see any connection between the law and opening locks using pick guns and bump keys, so maybe I have some explaining to do. In an average 5 pin Yale type lock there are five pin sets, each consisting of a key pin, a driven pin and a return spring, I have covered this in earlier articles on this site.  The effect we are looking for is to have all of the key pins below the shear line and all of the driven pins above the shear line, to enable the plug to rotate and the lock to open. 

Normally, with no key in the lock, the spring pushes down the driven pin onto the key pin and in the process blocking the shear line. What Mr Newton is in effect saying is if we strike the bottom key pin in the right way, all of the energy in that strike is transferred to the driven pin above it. The key pin does not move at all and thus stays below the shear line, but the energy imparted into the driven pin forces it upwards , above the shear line, against the return spring and when the forces equalise the spring starts to push the driven pin downwards again towards the shear line, BUT if it is the next binding pin, it actually gets trapped at the shear line, effectively clearing that pin set. In the case of the bump key, all pin sets are struck at the same time and with the same amount of energy .... and providing the acceleration of that strike equals or exceeds 1G, all pin sets clear on the same strike. So the perfection we are always seeking is "One strike .... and it's open !".  

OK back to our less than perfect swinging arm pick guns, which you can pay up to 1000 for .... and they still use a swinging needle !. Remember the case of the bump key, where all pin sets are struck at the same time with the same energy ? ...... well .... all modern pick guns cannot do that !. The problem is that they all use a swinging needle. The first problem with a swinging needle is that, since there is no fixed relationship between the axis of the pick gun 'needle' and the axis of the lock plug, what the needle strikes is a pure matter of chance on how the pick gun is held. The odds against you accurately aligning the needle for a parallel strike are slim to nothing and the only thing in your favour is that the pick gun strikes many times a second, increasing your chances of achieving your chances of striking all pins at the same time.

The other half of the story is if we want to get all of the driven pins to 'fly' above the shear line together, we not only have to strike them all at the same time, but also with the same amount of energy. A swinging needle pick gun cannot do this, no matter how much you pay for it !. The reason is that the needle describes an arc, which means that the pins at the back of the plug get struck at a greater velocity than those at the front end of the plug. The end result is that the driven pins do not 'fly' together and we enter a completely random situation, where physics fly out of the window. In short, the only time that we can hope for all of the pins to fly together is immediately after the first strike. That is why I am interested in the first strike situation.

The reason electric pick guns work is because of the manufacturing tolerances of the lock. Something you buy for a few pound cannot be expected to have the precision of a Swiss watch. The imperfections show up in the 'binding order' when torsion is applied to a lock. In the case of the pick gun we have no idea of what that binding order is, but rely on the fact that the next pin in the binding order will get trapped above the shear line, if the torsion applied to the lock is of the right order (invariably less than you think !). So using the pick gun you never know the order that the pin sets clear the line and why should you care so long as the lock opens. A large proportion of locks will open to the pick gun, but I am interested in those that do not.

I am rather hoping that the set of Klom pick needles I have ordered will arrive tomorrow, so that I can dimension the left hand end of the swinging arm, for the needle clamp.  There are about 20+ different needles in the set, including those for dimple and cruciform locks etc., which at the moment, look to me to be completely wrong in a swinging arm pick gun. however they look  full of possibility for the linear pick gun that does not yet exist !


12th February 2010

The Klom gun needles arrived. I was going to make a needle clamp today to fit on the end of the swinging arm to take a Klom needles, but there happened to be one in the needle kit. That is now fitted and that more or less wraps up the mechanical side.


Klom gun picks.

Originally I was going to make my own needles out of hacksaw blades, but then I found a Klom gun spares kit at Lockrus, which intrigued me !. The contents are shown below ....

In addition there was the straight needle, I have fitted to the home made pick gun, plus the blade clamp and screw. All for 15 including tax and postage. On the left are a total of 12 picks. An obvious thought is to make a handle to enable these to be used as a manual set, as well as in the gun. They are 0.5mm thick and therefore OK for European and Japanese locks

In the middle are four dimple picks, for picking dimple locks. There are some video's of them in use on Youtube and they appear to work OK, which does not say much for 'high security' locks that use side bars and security pins, such as spools, serrated  and mushroom pins. There were no instructions with the kit, so I am guessing that the two wire tools are 'wisks' intended for picking cruciform locks. Someone suggested that they are intended to fit into the electric drill attachment that comes with the Klom pick gun, but that does not make sense as you would end up with a mangled mass of wire !. However they would work in a linear pick gun with a reciprocating head, which is on my list of things to do.

The next four are odd and no one seems to know what they are for. As you can see they have a black plastic head, of irregular shape and round shafts.

The last thing on the right is, I assume a spare part for the gun. At the top is a 'tension wrench'  and an Allen key for the blade clamp.



The spares set was a very good buy at that price and I look forward to see what the picks can do in the real world.  I am not 100% happy with the first pick gun as it needs a bit of 'tuning'. As always, I keep moving the goal posts and have a feeling that I need to look at a design for a linear rake gun, that should give better results than a swinging needle. I think I have a spare solenoid of the same size, so perhaps I ought to do that next, if not I can canabilise the one above. A linear gun would also bring the rake key set back into play, as they are useless used manually.  Time for lunch !.