When I moved into my home many years ago, there was this lock-box mounted to the water main on the side of the house. I figured it was one of those used by real-estate agents to store the house key for viewings, but months passed and it still remained there. No one from my buyer’s agent’s office had a clue what this was, and the seller of the house had already moved out-of-state.
Recently, I had some plumbing work done, and that also included replacing the main water valve for the house, allowing this lock box to come free from the plumbing. Now inspecting it up close, and looking up the model online, I realized that it has an alphabet wheel and uses a three-letter combination.
As it happens, Thanksgiving weekend was upon me, and since I was bored, I figured I’d try all the possible combinations. Just 17,576 possible combinations, how bad could it be?
The most immediate problem was that due to being out in the elements, the dial did not turn easily. It would move, but was rather rough. And since the knob is only ~1 cm diameter, this is an incredibly un-ergonomic endeavor. I had to stop after the first 100 tries, due to the finger exhaustion.
Knowing this would be untenable for the long-run, I decided to build my way out of this problem. Since a combo lock involves making rotations that almost go all the way around, I drew inspiration from rotary telephone dials, where one’s finger starts with the intended number and then swivels the dial around.
But whereas a rotary telephone dial only needs 10 positions, I needed to fit 26 positions, one for each letter. I decided on each hole being 17 mm to comfortably fit any of my fingers, but that also dictated the overall diameter of the wheel. But that’s good, since a larger diameter wheel means more leverage to overcome the rough lock movement. It also happens to be that this wheel has a diameter of 180 mm, which is just enough to fit in the 200 mm bed of my 3d printer.
Using FreeCAD, I designed this wheel so that it fits around the splines of the lockbox dial, which held remarkably well. I had thought I would need Blu Tack or something to keep it together.
Using this wheel, I’m able to “dial” combinations much quicker using one hand, while holding the lockbox with my other hand to press the lever down to test the combination. This should be good.
(note: some parts of this story were altered to not give away identifying details)
Have you tried ‘AAA’ or a hammer?
If you haven’t done so, be sure to lube your lock
Send it to the LockPickingLawyer, he’ll open it with a wet towel and a stern look.
Or McNally, he’ll open it by smacking it with another lock.
Oh no, this is the safe thing all over again, isn’t it?
Im kinda hooked now what will be in it. Do post an update… Somewhere
We need a remindme! bot
There is one but it’s on a mastodon instance I can never remember the name of. But it will work with Lemmy if you remember the name to summon it.
@[email protected] 1 month
@[email protected] 1 minute
@pelespirit Ok, I will remind you on Wednesday Dec 3, 2025 at 1:08 AM UTC.
@pelespirit Here is your reminder!
sweet, it worked. @[email protected] dm 1 month
Neat! Thanks for testing it.
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Very clever!
Not to take away from what you’ve already made, but is there a reason you don’t want to automate the whole thing? 17k is a lot. Maybe I’m assuming too much, but if you have gotten this far I imagine you have access to most of what you’d need to not have to give yourself carpal tunnel.
Automation would have made this quicker, but I didn’t have on-hand any stepper motors nor microswitches to rig up a machine to try all combinations. Perhaps the greatest outstanding issue was how to actually press down the lever to “try” each combination. That would require some sort of solenoid, and at that point, I figure this will just be a passive manual activity, to do when watching TV or winding down before bed.
As for carpal tunnel, the design is meant to reduce that risk, because this wheel minimizes finger manipulations. Indeed, without using any fingers, I could turn this wheel using a pen, Cruella De Ville’s cigarette holder, or any number of other instruments that replaces a finger. If nothing else, because the diameter is 180 mm, turning this thing is more of a forearm exercise. I actually considered adding a spinner knob, like those used on an automobile steering wheel.
That’s totally understandable. What you’ve made already seems like a huge upgrade, especially seeing as you went in planning to do it all unaided. I hope you update us once you’ve got it open. I’m keen to know how it goes. Thank you for sharing!
The spinner wheel in the top picture of that website is giving me intrusive thoughts about the airbag. The ones actually listed for sale look much safer, but that first one looks like it would just kill you.
I feel involving a motor is a significant step forward in this project, still. Could be my inexperience talking, haven’t done a lot with small motors, but while 17,000 is a lot, it’s a job that only ever needs to be done once.
If I were to go about automating it, I feel like there’s a decent chance that I misalign something and it “completes” the full set without unlocking.
Very true that it would involve added layers of complication. If it were me and I had one a small motor handy I would probably try it anyway. I figure worse case it runs through unsuccessfully and then I just do it manually after. If you don’t have one around that’s a different story, but Im’m also old and my hands aren’t what they used to be. I can definitely see it being a fun distraction to do it manually though. Either way I’m sure what you’ve made will be a great help. Hope you report back when you open it.
Edit: just realized you’re not OP. My bad, but your point still stands.
Yeah, not OP, but I’ve done the same. Got a bike lock for free once because the owner forgot the combo. 4-digit number, so just a thousand possibilities, and I fidgeted with it for maybe 3 hours over a few days, got a free bike lock. Excellent value, I needed one.
I also hope they report back, I’m curious.
I brute forced a 4 number lock during stand-ups at work, took me a couple of months. It was on some sort of box with 3 drawers, on wheels and nobody had the code.
What was the prize?
Old stickers, a couple of usb keys IIRC, some pens, and a roll of scotch(tape) with the old companies name.
Nice 😎 must have been satisfying to finally crack it.
Ha ha yeah I didn’t pay too much attention to the meeting after that
A lot of these kind of locks can tolerate a fuzz of a digit or so. I’d use 13 instead of 26 maybe.
I’ll save ya some time, its always BOB
I tried that just for you. Sadly, it didn’t open.
I’m going with initials rather than a word.
My first guesses would be ass, tit, or dik/dic.
You can probably put your ear to the back of it and pick it that way.
Have you treated it with anything to make it move easier?
Does that make it easier or harder to feel when it clicks into a set point?
There’s no clicking unless I press down the lever, and I think they’re added features to this thing which feel like a set point but are false.
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I would really try to mechanically defeat this rather than brute force it. Something like this method:
Also, the gates on these are ALWAYS bigger than one letter, so you could probably actually go with 13 places on the dial and cut your work in half.
Your mind is going the right way, but your math is shit.
It’s more of a logarithmic equation. 26 positions would be 17,596. But 13 positions is only 2,197. Much, much easier.
