Simplex 5-button combination locks:

*Hobbit*'s in-depth evaluation

Contrary to what the marketing reps would have you believe, the locks can be
opened fairly quickly without knowing the set combination and without damaging
the lock. Through a blend of a soft touch, a little hard logic, and an
implicit understanding of how the locking mechanism works, they generally
yield within five minutes or so. [There are *always* exceptions...]

This method requires that one does not think in terms of a sequence of button
presses. One must think in terms of tumbler positions, and simply use the
buttons to place tumblers where desired. For practical description purposes,
it will be assumed that the buttons connect right to the tumblers, rather than
the idler gears that they really do. The idler gears are a necessary part
only during combination changes. Unless you are doing a change, considering
it this way is pretty close to the facts. Remember that a 0 position means
the button was never pushed, and 5 is enabled and shifted as far as possible.

Turning the thumb handle to the right [clockwise] raises the locking bar
against the tumblers. Since the lock is never machined perfectly, one or more
tumblers will have more pressure on it than other ones, and this shows up as
friction against it when it is turned via the button. This friction is felt
in the short distance between fully-extended and the detent on the button [the
first 2 or 3 mm of travel]. Some will travel easily to the detent, and others
will resist efforts to push them in. Suppose you are twisting the handle, and
tumbler 1 has lots of pressure on it [you can feel this when you try to push
button 1 in]. When you back off the tension on the handle a little bit, the
button can be pushed in against the resistance. The fact that the button has
resistance at position 0 tells you that tumbler 1's proper position is *not*
0, or there would be no pressure if the notch was there! Upon pushing button
1 in, you find that no pressure has appeared at any other button. This
eliminates position 1 for tumbler 1, also. Now, how do you get tumbler 1 to
different positions so you can test for pressure against other ones? Push
subsequent buttons. Push any other button, and tumbler 1 advances to position
2. Ignore what the other tumblers are doing for the moment. Now, perhaps
another button has some resistance now. This means that tumbler 1 is either
at the right position, or getting close. Basically you are using othertumblers
to find out things about the one in question. [Keep in mind that the first one
with friction won't *always* be tumbler 1! Any tumbler[s] could have the first
pressure on them.] Continuing, push another "don't care" button. A "don't
care" button is one that is not the one you're trying to evaluate, and not the one
that recently showed some friction. What you want to do is advance tumbler 1
again without disturbing anything else. Did the pressure against your test
tumbler get stronger, or disappear? If it got stronger, that points to an even
higher probability that tumbler 1 is supposed to be at 3, rather than 2. If the
pressure vanished or became less, 1 has gone too far, and you were safer with
it at position 2. Let's assume that the pressure against your test tumbler
increased slightly when tumbler 1 was at 2, increased even more when tumbler
1 was at 3 and vanished when you pushed it onward to 4. Reset the lock. You
now know the proper position of tumbler 1 [that is, whatever tumbler first had
pressure on it]. You've already drastically reduced the number of possible
combinations, but you aren't finished yet.

You can now eliminate positions for the next one or two tumblers the same way
-- but to set things up so you can feel the pressure against these, you must
ensure that your newly-known tumbler [1 in this case] is in its proper position.
It is useful to make a little chart of the tumbler positions, and indicate the
probabilities of correct positions.

---Positions---
0 1 2 3 4 5
----------------
1 : L L + T L | <-- Indicates that tumbler 1 is not
0, not 1, maybe 2, more likely 3.
2 : | | | | | |
3 : | | | | | |

4 : L | | | | | <-- Indicates that tumbler 4 is not 0.

5 : | | | | | |

This chart is simply a bunch of little vertical lines that you have drawn in a
5x6 matrix; the topmost row corresponds to button 1 and the lowest to 5. Mark
the probabilities as little hash marks at the appropriate height. The leftmost
bar indicates position 0, rightmost 5; a high mark on the left side indicates
that that tumbler is 0, or is never used. The relative heights of your tick
marks indicate the likelihood of the notch on the respective tumbler being
there. If you don't know about a position, don't mark it yet. This chart
serves as a useful mnemonic while learning this trick; as you gain experience
you probably won't need it anymore if you can remember tumbler positions.

A tumbler at the 0 position is already lined up before any buttons are pressed.
This will feel like a lot of loose play with a little bit of pressure at the end of the
travel, just before the enable detent. Be aware of this; often enough the first
button with pressure can be a 0, and if you aren't watching for 0 positions you
can easily assume it's a don't care, push it, and ruin your chances of feeling
others. Make sure your "don't care" test buttons aren't supposed to be at 0
either. It's a good idea to run through and try to find all the zeros first thing.

Let us continue from the above. You have found that tumbler 1 is most likely to
bet at position 3, with a slim chance of position 2. This is marked in theabove
chart. The reason this can happen is that the tops of the locking bar teeth are
slightly rounded. When the tumbler is one away from its opening position, the
locking bar can actually rise higher, since the notch is halfway over it already.
So don't assume that the first increase in pressure on other buttons is the right
position for the one you're finding out about. Let's assume that the next
pressure showed up on button 4. You can feel this when tumbler 1 is at position
3; to get tumbler 1 out there, let's say you used the sequence 1,2,3. 2 and 3
were your "don't care" buttons used only to push 1 around. Therefore now,
tumbler 1 is at position 3, 2 is at 2, and 3 is at 1. And 5 and 4 are at 0, and can
therefore be felt for pressure.

The next step is to find the proper position for the next button with pressure
against its tumbler. Many times you'll get more than one that exhibit
pressure at the same time. Figure out which button has more pressure on it
now with your first tumbler in the right position. In this example, only 4 applies.
You now want to advance tumbler 4 to different places, *while* keeping 1 at its
proper place. 1 must always advance to 3 to free the locking bar enough to
press on other tumblers. To place tumbler 1 at position 3 and 4 at position 1,
you would do something like 1,2,4 and check 3 and 5. To place tumbler 1 at
position 3 and 4 at 2, you would do something like 1,4,2. To place 1 at 3 and
4 at 3, you have to press 1 and 4 at the same time, and then advance that mess
by two positions. If you use 2 and 3 for this, the notation is (14),2,3, which
means 1-with-4, then 2, then 3. You can also do 4,1,2,5 to put 4 at 4 and
check 3. If all these tests fail, that is, no pressure appears at any other button,
you can start assuming that 4 is supposed to be way out there at position 5.
For the example, let's say you did 1,4,2 and pressure showed up on button 3.
To double-check this, you did (14),2,5, and the pressure on 3 went away. So
tumbler 4 must have gone too far that time. Place a fairly high tick mark on the
chart at tumbler 4, position 2 to indicate the probability.

Note: A better way to do that last test, to avoid ambiguity, is to do 1,(42),5 and
check 3, then do (14),2,5 and check 3. This ensures that the only change
you have made is to move tumbler 4 from 2 to 3 an avoids the possibility of
movement of tumbler 2 giving bogus results. Through the entire process, you
want to try to change one thing at a time at every point. Sometimes one of
this sort of possible test setup won't tell you anything and you have to try
another one [in this case, perhaps 1,(45),2 and then (14),5,2 while checking 3.
This has simply swapped the positions of 2 and 5 during your testing].

You now know two tumbler positions, with a high degree of confidence, and
have further reduced the possible combinations. From here, you could mix
tumblers 2,3 and 5 into the sequence with various permutations, as long as you
place 1 and 4 correctly every time. This would still take some time and brain
work ... let's try to find out something about some other buttons. Place 1 and 4
where they're supposed to go ... the sequence 1,4,2 will do it, and see what's
up with the other buttons. 1,4,3 will leave 2 and 5 available. You find
eventually that 2 and 3 have the next bit of pressure distributed between them
(and are nonzero], and 5 feels like a 0, as described above. To confirm this,
advance 5 along with some other button and check 3. Bingo: There is no
pressure on 2 when 5 is enabled [and you have not changed anything else
besides 5's position], so you can firmly decide that 5 is 0 after all. So leave it
there. [You did this by advancing 1 to 3 and 4 to 2, as usual, so you can feel
2's pressure in the first place.]

By now you should know the proper positions of three of the tumblers, and have
eliminated any other zeros by feeling their initial pressure. Now, since 2 and 3
have the next pressure on them, try and find out more about them. You know
they aren't zero; suppose we try 1? To do this you must get one of them to 1,
1 to 3 as usual, 4 to 2, and leave 5 alone. How? Use hitherto unknown buttons
as dummies to position the tumblers right. For instance, the sequence 1,4,3 will
do what you want here; you then check pressure on 2. Or 1,4,2 and check 3.
Here you may notice that the pressure on the leftover is a *little* stronger than
before, but not enough to make any sure judgement. Well, now you want to
advance an unknown to position 2 - but you suddenly notice that if you do
[by doing something like 1,(42),3] there are no free buttons left to test for
pressure! 'Tis time to try possibilities. Your only unknowns are 2 and 3 now.
You must now advance 1 and 4 to their proper positions, leaving 5 alone, while
sprinkling the unknowns around in the sequence in different permutations. Use
your chart to remember where the known tumblers must go. Sometimes you get
two possibilities for a tumbler; you must work this into the permutations also. In
this particular example, you know that either 2 or 3 [or both!] must be the last
button[s] pressed, since *something* has to get pressed after 4 to advance 4 to
position 2. An obvious thing to try is putting both the unknowns at position 1 by
doing 1,4,(23). Try the handle to see if it's open. No? Okay, now leave one of
the unknowns down at 1 and mix the other one around. For instance, for 2 at 1
and 3 at 2, you do 1,(34),2 -- nope. Advance 3 one more; (13),4,2 *click* --
huh?? Oh, hey, it's *open*!!

Well, when you are quite through dancing around the room, you should know
that your further possibilities here ran as follows:

3,1,4,2 ; to end the
permutations with 2 at 1

1,(24),3 ; and permutations involving 3 at 1.

(12),4,3

2,1,4,3

One may see how things like 2,1,(34),x are eliminated by the fact that 1
must get to 3, and 5 must stay still. Since only 4 buttons could be used, no
tumbler can get to position 5 in this particular combination. Note also that
the farther *in* a tumbler has to go, the earlier its button was pressed.

If all this seems confusing at first, go over it carefully and try to
visualize what is happening inside the box and how you can feel that through
the buttons. It is not very likely that you can set up your lock exactly as
the example, since they are all slightly different. Substitute your first-
pressure button for the 1 in this example. You may even have one that
exhibits pressure against two or more tumblers initially. Just apply the
differential-pressure idea the same way to find their most likely positions.
The example is just that, to demonstrate how the method works. To really
understand it, you'll have to set your lock up with some kind of combination,
and apply the method to opening it while watching the works. Do this a few
times until you understand what's going on in there, and then you'll be able
to do it with the lock assembled, and then in your sleep, and then by just
waving your hands and mumbling....

A 5-press combination makes life a little tougher, in that you lose
versatility in your freedom of test positions, especially if your first-
pressure tumbler is at position 5. Here you can use the "almost" feature to
your advantage, and advance the errant tumbler to one before its proper spot,
and hope to see increased pressure on other tumblers. When a tumbler is one
away from right, the locking bar tab is hanging a large section of itself into
the tumbler notch, and the tab's top is slightly rounded. So it can rise a
little higher than before. If you twist the handle fairly hard, you can
distort the locking bar slightly and make it rise higher [but don't twist it
hard enough to break away the safety clutch in the shaft!] The chances of
someone setting this sort of combination without prior knowledge about the
*specific* lock are almost nonexistent.

As if that wasn't enough, the next thing to deal with is the so-called
"high-security" combinations involving half-pushes of buttons. The long
initial travel of the tumbler permits this. If you look at your open
mechanism and slowly push in a button, you'll see that the tumbler actually
travels *two* positions before landing in the detent, and further motion is
over one position per press. There is no inherently higher security in this
kind of combination; it's just a trick used against the average person who
wouldn't think of holding a button down while twisting the latch release.
It's quite possible to defeat these also. When you are testing for pressure
against a tumbler set at "one-half", you'll feel a kind of "drop-off" in which
there is pressure initially, and then it disappears just before the detent.
Before testing further buttons, you'll have to "half-enable" the appropriate
"one-half" tumblers so the locking bar can rise past them. Set your lock up
with a couple of combinations of this type and see how it works. Note that
you must hold down the "half" buttons just before the detent click while
setting or opening. This makes an effective 7 positions for each tumbler, but
in a standard [no "halfs"] setup, it's effectively 6. This is Simplex's
"high-security" trick that they normally only tell their high-dollar military
customers about. After working the lock over for a while, it's intuitively
obvious.

The Unican type has no direct pressure direction of twist; if you turn too
far to the right you only reset the tumblers. What you must do is hold the
knob against the detent release just tight enough to press the locking bar
against the tumblers inside the box but not hard enough to slip the detent.
There is a fairly large torque margin to work with, so this is not difficult
to do. Unicans do not twist to the left at all, so ignore that direction and
work clockwise only.

Possible fixes

The obvious things improvements to make are to cut notches of some kind into
the locking bar teeth and the tumblers, so that the pressure can't be as
easily felt. Another way might be to have a slip joint on the locking bar
that would release before a certain amount of pressure was developed against
it, and thus never let the tumblers have enough pressure against them to feel.
The future may see an improved design from Simplex, but the likelihood does
not seem high. They did not seem interested in addressing the "problem".