Prop Tutorial: Matsumoto’s Lockpick Bracelet from Cowboy Bebop

“I’m always amazed people think valet keys will keep anything safe” – Matsumoto


Watching Cowboy Bebop (Live action), there’s a shot where Faye’s mother Matsumoto slips off her bracelet, and hidden within is a lock pick set! I immediately fell in love with the concept, and started planning out the build in my head.

The first step was to work out rough sizing. I drew a circle in Solidworks and laid out a pentagon around it – matching the design from the show. Solidworks is pretty pricey if they don’t sponsor your Hackerspace with a license (Thanks Dassault!), but you don’t actually need it - I just used it because it was a quick way for me to get a basic idea. I laser cut the parts out of scrap plexiglass, built a few test bracelets in different sizes, and they were all terrible. Turns out wrists aren’t pentagon-shaped, so the corners constantly caught on things, and the whole bracelet was far too bulky. While accuracy was a priority, I wanted to make this real, and real meant usability was the main priority. After playing with a few different polygons, I settled on a hexagon as the most comfortable shape. If you want to go with the original pentagon, you should be able to modify your part order to do so. I believe in you!

Test bracelets showing various design options
Test bracelets showing various design options

The drawings are sized to my 6.5″ wrist, but these plans should work for anyone with wrists between 5.5″ and 7″ in circumference. If you have larger or smaller hands then that, you can modify the DXFs and get a perfectly sized bracelet, but I recommend doing a test piece before ordering (even if it’s just printed out on paper and cut with scissors, having a tangible representation is super helpful).  After working out the body of the bracelet, I had to design the picks themselves. I could claim I did a bunch of engineering and research… but I didn’t. I googled some pictures of a rake and a hook that looked like my favorite pics, and traced them in Inkscape. As dumb as it is, Inkscape is my favorite 2d cad program for doing anything artistic, and it’s free.  Just make sure to export your DXFs in “inches” or “mm” and not “pixels” – or your SCS order (more details on that soon) will be far more expensive and comically large. To complement the pics, I needed a removable tension wrench. This isn’t shown in the show, but in my goal of making it usable I decided to go for it.

The key parts of the bracelet – Lock picks and the Tension wrench/holder

So. Design is great and all, but how do we make this real? That’s a lot of metal shaping, and I sure don’t have a laser that can punch through a brass… But do you know who does? SendCutSend! SCS will take your DXFs, turn them into metal parts, and send them to you for a very reasonable rate. I swear this isn’t a sponsored post…. but I am trying to suck up enough to get a SCS sponsorship for a BattleBot, so….. Moving on! I’ve used SCS for personal projects for a long time, and love how much time it saves. And I’m about to save you a bunch of time, because I’ve uploaded the entire bracelet partslist into a public cart, so you can order them without uploading the files manually.  There’s always coupon codes for 10-20% off, so do a quick search for those before you order (or try NORUSH15).  I think the order comes to about $22 (very reasonable!), but there’s a $29 minimum order.  I deeply recommend just drawing something fun in inkscape and uploading it to get your cart over the $29 mark.


Pick parts:

  • Direct cart to order from SCS:
  • Note: This has versions of the long sides, with and without scallops. You’ll want to delete one of the options, or change quantities to get 2 of each.
  • Note: This does not include the washers, since they’re too small for auto-approval, You’ll have to upload them from the DXF or dig some out of your stash
  • DXFs if you want to DIY, use another supplier, modify, or add the washers:

Magnets: – optional, see below.

Rivets: – This was enough to do 2 bracelets, in brass, with enough extra rivets to last me years.


Your send cut send order should look something like this! This is parts for two bracelets and a a disk for another project.  

First, file the edges of the brass components. There’s a little edge where the laser starts/stops, leaving a sharp spot on each piece. Luckily, a few seconds with a file or sandpaper will take care of it.


20220124_182507 (Medium)
Next, we want to lay everything out. It’s very important that we have the long brass sides immediately over and under the picks / wrench, this keeps everything tight and held in. The rest of the layout follows from that. I was trying different magnets in this picture, but the layout is correct.   
20220124_184838 (Medium)
Layout for inline magnets, riveted, or lathed connection (see below for details)
Layout for offset, face-to-face magnets
Now, we’re going to rivet everything together. I chose to start with the lockpicks, work towards the wrench, and then do the endlinks.  Thread the rivet through all the layers, put a cap on it, lay it in the anvil, and bash it decently hard. I was worried it would take a delicate hand, but I just smashed it until it was flat and it worked great. Despite what I show in the image, I didn’t even use the press tool, just whacked the rivets directly. (Note, You’ll notice I messed up the layout here. I make these mistakes so you don’t have to!)  
20220124_181518 (Medium)
Now, repeat this the whole way around the bracelet!
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For my Bracelet, I lathed a turned a cylinder with nubs for the closure on our lathe.
20220124_192138 (Medium)

Now that you are at the ends, you have to make a choice.

  • If you have skinny hands, you can rivet the ends together and slip it on and off.
  • If you have a lathe, you can turn up a little cylinder with nubs on the end, so that the bracelet will snap on and off.
  • But the easiest option is to use magnets. You can either align them so that they will attract on the edges, or on the face.
  •            If you choose edges you get:
  •                       Good holding strength,
  •                       Slight asymmetry.
  •            If you choose faces you get:
  •                       Great holding strength,
  •                       Symmetrical design,
  •                       A bit of a twist in it.


You can mock up the options before you attach them to see how they feel, but either way, just rivet them on there like you did the rest of the bracelet. I was afraid they’d be brittle and shatter when being hammered, but they took the beating just fine.


That’s it! Now onto the next project: Learning how to pick locks.


Wrestling with Filament on your 3D Printer?

My Solidoodle 3 printer finally came in last week and I was able to pretty much plug it in and start printing. I immediately noticed that something needed to be done about the filament spool. With it being a new spool, the filament was just falling off  at the slightest turn on the PVC holder which was really annoying because that meant I had to babysit it. So with a small filament holder I found on thingiverse and some old folders, I was able to come up with a solution that allows me to hit ‘print’ and then just walk away until my print is done.

Multirotor Acronyms, Terms, and More…

I’m learning about Quadrotors, Tricopters, Hexacopters, and other multirotors and I have noticed that there are a bunch of acronyms, terms, and definitions that I don’t know. This is typical when learning any new hobby.  So this post is simply a list of those acronyms and terms along with a few photos and definitions. I will add more as I come across them. Feel free to leave anything I missed in the comments section and I will add it to the list.  Click on More to view the entire list.


ARTF – Almost Ready to Fly
BEC – Battery Elimination Circuit
BNF – Bind-N- Fly
ESC - Electric Speed Control
GPS – Global Posistioning System
FC – Flight Control Board
FFF – Fast Forward Flight
PNP – Plug and Play
RTF – Ready To Fly
RTH – Return To Home
RX – Receiver
TX – Transmitter

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Back to Basics: Ohms Law

During last night’s Open Hack Night, while trying to explain things like how transistors and mosfets work, it was discussed that maybe taking a step back and outlining some of the basics of electronics would be beneficial to everyone.  So I decided to start with Ohms Law.

There are 3 things that Ohms Law deals with, and they are all related to each other.  Those things are Voltage, Current and Resistance.

Voltage is measured in… well Volts of course!

Current is measured in Amperes.

Resistance is measured in Ohms!  Named after this guy who put a bunch of work in discovering resistive properties electricity, and apparently came up with this relationship known as Ohms Law.  Anyhoo.

I like analogy’s to help me relate things that I know, against things I don’t know.  So everyone’s favorite analogy of electricity is water.  Some will argue this topic to death, but for my purpose I’m sticking to it.

Voltage — So Voltage is actually a potential concept, think of a large water tank on the top of a hill and a small pipe coming out of the bottom.  The difference between what is coming out of the pipe versus the pressure in the tank is the potential voltage.  So voltage is the pressure.

Current — This would be the volume of water pushed through that pipe by the voltage (pressure) and would refer to the quantity of water flowing through it.

Resistance — So this would be the pipe its self.  The larger the pipe (lower resistance), the easier current can flow through, thus having more current.  The smaller the pipe (higher resistance), the harder it is for the current to flow through the pipe, yielding less water.

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The little gerber viewer that could!

Of course I’m talking about gerbv!  For those of you who don’t know, gerbv is a free Gerber or RS-274X viewer that comes from the gEDA Project.  It’s free, it’s open source, it’s cross platform… (quick link to windows version download here) and that’s awesome.

So, why do you care?  Well, if you are building your own circuits and want to get a PCB made then usually the format you’ll need to export your design into is a gerber.  The reason you should grab gerbv is to double check for errors.  When you design a PCB in your favorite circuit layout tool, whether it be Eagle, Altium, or my favorite DipTrace, you should double check for errors.

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