A comment on my last YouTube video pointed out that the SL(2,3) group expressed by the Quaternion Cube is isomorphic to the group formed by multiplication of the unit Hurwitz quaternions.
Simulator
‘Order’
There are five different orders of unit Hurwitz quaternions: 1, 2, 3, 4, and 6; On the puzzle, the order represents how many times a sequence must be repeated to return to where you started.
STL Files: https://quirkycubes.com/public/QuaternionCube_STL.zip
Sticker Template: https://quirkycubes.com/public/QuaternionCube_Stickers.eps
Hardware required:
- 5x M3 Springs (~10mm uncompressed)
- 5x M3 Washers (6.9mm dia)
- 5x M3 x 16 Screws (button or socket)
- 12x M2 x 8 Button Head Screws
- 8x M1.6 x 16 Socket Head Screws
- 7/64" drill bit
I printed my copy out of ABS and vapor-smoothed it to post process it. I don’t see any reason that it wouldn’t work in PLA, but you will need to sand the edge hooks a little to get smooth motion. Here are the settings I use on a Bambu P1S:
DoDot M12
The DoDot M12 is a twisty puzzle that mechanically demonstrates Mathieu group M12. It’s a modification of my original vertex-turning dodecahedron where sets of three turning axes are geared together internally. This gearing was chosen to greatly reduce the number of possible permutations of the ‘dot’ pieces, which behave according to the rules of the 12-element M12 permutation group. The edge pieces of the puzzle behave as 6 disjoint orbits of 5 pieces, which makes them easy to solve. I greyed out the petals to avoid making the puzzle too complicated.
Glaze Material Substitutions
This page provides a set of calculators to help with calculating common material substitutions in glaze recipes.
Warning: These calculators are based on theoretical UMF analysis of the materials, and I have not verified them experimentally. Oxide analysis isn’t the only factor that determines how a material will behave in a glaze.
Each calculator allows for conversions between two material forms. Click “Switch” to toggle the conversion direction. Red cells indicate that a material should be subtracted from the recipe.
Wrapping vector artwork around a conical object in Inkscape
Free vector editing tools are pretty lacking in intuitive ways to wrap a template around a conical object (i.e. mug or vase). I aim to produce a vinyl decal that can be applied perfectly to a ceramic piece without any stretching.
This post is not a step-by-step procedure, but rather a general overview of the steps that I use to fit vector artwork to pieces of pottery using Inkscape and a vinyl cutter.
Current development builds for KiCAD 7 include the new constraint keyword physical_hole_clearance for detecting hole and pad collisions within a common net. This is useful for detecting via-in-pads which are often undesirable, as some PCB vendors upcharge to plug vias that could cause wicking during assembly.
To set up the custom design rule, first install a nightly build of KiCAD (6.99). Please note that saving a project with a development version of KiCAD will prevent older versions from opening the PCB file. To prevent this, I run the DRC from KiCAD 6.99 and make the necessary changes from KiCAD 6.
I bought a spool of Protopasta iron-filled PLA to test in a project where I need to fit a flyback transformer into a confined space. The prototype will likely be 3D-printed in PLA plastic and contain some moving parts wrapped in magnetic wire for power transfer.
For optimal performance, flyback transformers are generally wound around a ferrite core, which has high magnetic properties but low conductivity to reduce eddy currents.
This bug is fixed in Java 23u10
I came across an apparent bug in java.util.zip.ZipInputStream where reading a certain type of zip file causes an exception:
java.util.zip.ZipException: invalid entry size (expected 0 but got 199 bytes)
at java.util.zip.ZipInputStream.readEnd(ZipInputStream.java:384)
at java.util.zip.ZipInputStream.read(ZipInputStream.java:196)
at java.util.zip.InflaterInputStream.read(InflaterInputStream.java:122)
The file in question reads fine using archiving utilities and Java’s ZipFile, so the issue is likely rooted in ZipInputStream. My application requires reading the zip file sequentially, so ZipInputStream is my only option besides a third-party library. I decided to search for a solution using vanilla Java rather than pulling in a new dependency.
This post will be continuously updated with useful commands related to HTTP.
Python3 HTTP Server
Launches an HTTP server in the current directory for serving files
1python3 -m http.server [port]
cURL - Post Multipart Form
Post two files
1curl -X POST -F "file1=@file1.png" -F "file2=@file2.png" --no-buffer https://chandler.io/test
