Anniversary cabinet with a wooden combination lock

The cabinet was made as a wedding gift for my son and daughter in law. The cabinet itself follows conventional design and construction techniques - what makes the anniversary cabinet different is the combination locking mechanism.  The four drawers require you to know a code (combination) in order to open them.  Each drawer has a different combination. The idea then, is to give the combination for one drawer at a time (on the wedding anniversary).  To get things going though the combination for the first drawer (the bottom one) is given "free" at the time the gift is presented so that the general operation can be explained and tested. In this case the guests at the wedding reception were given a sheet of paper and an envelope so that they could write a note to the bride and groom. The envelopes were sealed and placed at random in the top three drawers.  So on the anniversary when the combination is revealed the contents (envelopes or other gifts) can be accessed.  Of course this may not work as intended, as the level of bribery re getting the combination early could come into play.

The video below shows how the combination locking system works and the Steps following the video give details on the construction of the cabinet and the locking system.

Step 1: Video showing how the combination locking system works on the anniversary cabinet

Comments

[gtramp]

Love it, so many little details, very skilled and thoughtful

[nlinventor]

gtramp - Thanks!

[kaway27]

Great ideas and nice design. If you have numbers instead of little dots on each node, it would be easier for you to remember the combination.

[nlinventor]

Right now I refer to points of the compass when I am thinking or talking about the different settings. But numbers would definitely be easier.

[mrmath]

Assuming 8 positions for each "flat", there would be 8 possible combinations if you had only one locking bar.

If you had two, you'd have 8 * 8 combinations (8 positions for the second bar for each of the 8 positions for the first bar), or 64 combinations.

if you had three locking bars, you'd have 8 * 8 * 8 combinations (all of the combinations you had for the first two bars would be repeated for each possible spot on the third bar), or 512 combinations.

Continuing on, each bar adds a factor of 8 to the number of combinations, for a total of 8 * 8 * 8 * 8 * 8 * 8 * 8 = 2,097,152 possible combinations.

But, if you take into account that your "flats" don't have to be exactly on the eights, and really wherever you felt like putting them, then you have an infinite number of combinations.

[klincecum]

1048576, because the exact opposite position also opens it. Divide by 2 :)

[Lorddrake]

actually it would be 823,543

if there are 8 positions on each spindle (not using any positions in between pips)
2 of them will open the lock and 6 will not.

so if we combine the 2 opens into one permutation (since if it is in either position it will open) and take the 6 locked positions that will give us 7 per spindle


7 * 7 * 7 * 7 * 7 * 7 * 7 = 823,543

[mrmath]

You're treating the two separate opens into one. You could do the same with the ones that don't open, saying that they are just.

Let's do a simplified example of two knobs. Assume the first knob opens on 1. That means it would also open on 5, but wouldn't on 2, 3, 4, 6, 7 or 8.

Now the second knob opens on 2, and therefore also 6, but not on 1, 3, 4, 5, 7, or 8.

You have 8 * 8=64 possible combinations of numbers. But only the combinations 1,2; 1,6; 5,2; 5;6 will open it.

We still have 64 combinations. The fact that you have 4 solutions instead of just one, doesn't change the number of combinations.

[Lorddrake]

so that would give you 1,048,576 combinations and 128 possible solutions?

your gunna need more drawers Nlinventor :)

[nlinventor]

Interesting math discussion - will wait in case there is a new number before I setup to make a zillion drawers :)

[mrmath]

Good catch. If the cutouts were offset, you would have the 2+ million, but with the offsets centered, you do have to divide by two, and you end up with your number.

[nlinventor]

Like the 2 million plus but like infinity even better! Thanks!

[mrmath]

You're welcome!

[Lorddrake]

5 stars

amazing concept

[nlinventor]

Thank you very much Lorddrake. Really appreciate it.

[Haunted Spider]

This is ingenious. I love the design and the thought that went into it. The lock mechanism is a work of art. Did you design the lock yourself or is it based off of a model? Either way, the details you put into it are incredible.

[nlinventor]

Haunted Spider - Yes I designed the locking system myself and this is the second generation of the idea. The first cabinet (a totally different cabinet design as it was a jewellry cabinet) worked fine but it was easier to "break the code" as it didn't have the secondary locking system (closing the lock rod cover to enable opening the drawers). Thanks for the comments!

[meralgia]

how will you prevent the recipient of the cabinet from watching the video? if you pause it just so, it would be pretty easy to steal the combinations ahead of time.

[nlinventor]

They already knew all combinations before I did the video and instructables. It's hard to keep a secret!

[poofrabbit]

This is very cool, since you have a secret compartment you might think about trying to enter it into the spy contest too! Wish I had wood tools, this is very very cool and I would love one! Nice idea, execution and instructable! 5 Stars!

[nlinventor]

I'm posting pictures of the three secret compartments on the actual wedding anniversary - today! All three compartments have false bottoms. The center one is accessed using a magnet or magnetic material. The left and right hand false bottoms are raised by pressing down on the back of the false bottoms. I just posted a video on youtube showing all of this. You can view it here: http://youtu.be/OAZMn_OmYuw

[nlinventor]

BUT WAIT, THERE'S MORE!

Not obvious unless you remove a drawer and look at the bottom. Each drawer has a collage of family pictures secured in place with a plexiglass cover.

[nlinventor]

Thanks poofrabbit! Also thanks for the suggestion re entering into the spy contest. Do you know the process to do this for my project... what I'm wondering is should I modify the current entry to add the secret compartments (I thought I read somewhere that you are not allowed to add photos/videos after the project is published?) or would I have to do a completely new instructable showing the secret compartments?

[Servelan]

Lovely cabinet - worthy of being passed down. Might be handy to document the combination somehow on the piece, but ordinarily hidden so that it doesn't become a variant of The Musgrave Ritual: 'Whose was it?' 'Grandpa's' ... 'How was it opened?' 'First the second, then the fourth, then six and three'. : )

[nlinventor]

Good point. Not shown in the instructable are three separate "secret" compartments - maybe put the combinations there - oh yeah, probably not a good idea :)

[mrmath]

Gorgeous would work, and an evil, evil idea! :)

[nlinventor]

Thanks mrmath - I didn't mean to be evil though :). With your user name maybe you can answer the question re the number of combinations (no pressure though).

[mrmath]

I just posted the answer as a new comment, and can't delete it for some reason. But it's there for you.