3D-printed caps for protruding bolts

When I attached our children’s swing to the ground there was still a significant piece of sharp-ish threaded metal sticking out above the bolt head and I was worried about them falling on it. Grinding the end off might still leave some sharp parts, so I thought it safer to print plastic covers for them.

I designed the caps using OpenSCAD, using the ScrewsMetric library for the bolt-shaped inset.

You can see the source code for the design in this GitHub gist:

include <ScrewsMetric/ScrewsMetric.scad>;

$fn = 30;
GHOST = false;
outer_size = 40;

difference() {
    sphere(d = outer_size);
    translate([-outer_size/2,-outer_size/2,0]) cube(outer_size);
    translate([-outer_size/2,11,-outer_size+1]) cube(outer_size); // cut
    rotate([0,0,30]) translate([0,0,0.002]) BoltNormalWithSurface(hexHeadBolt, M12, 15+0.002);

The biggest challenge was to find an acceptable compromise in shape and size:
– tall enough to cover the top of the bolt
– narrow enough base to fit next to the swing’s leg
– should be printable without overhangs and no need for supports

The final design I went with is a bit different from in the photo above because that one didn’t fit. I kept the size the same and chopped off one side of the dome to leave space for the swing’s leg.

You can download the generated STL files for printing from the Thingiverse website.

It printed really well and I stuck the pieces in place with some leftover silicone.

3D Printed Hungarian Cross

The Hungarian coat of arms features an iconic cross with two horizontal beams. In Hungarian it’s called “Kettős Kereszt” which translates to “Double Cross”, usually called the Patriarchal cross in English. This cross is present on other emblems around the area of Central and Eastern Europe too and has been featured on the Hungarian coat of arms at least since the reign of King Saint Stephen of Hungary.

3D model of the patriarchal cross as shown on the Hungarian coat of arms

3D model of the patriarchal cross as shown on the Hungarian coat of arms

Seeing as it’s a Hungarian national holiday today, in memory of the heroes and martyrs of the Hungarian revolution of 1956, everyone has their Hungarian flags out. I decided to do something Hungarian too, while trying out some tools for preparing models for 3D printing. So far I’ve been using Blender, because I have some experience with it, but it’s for creating 3D scenes and although you can use it to design 3D models for printing, it’s not CAD software. This time I tried Autodesk’s web-based program Tinkercad, which although lacking many of the features you’d get in a full-blown CAD program, is plenty enough for me to design simple things like this. Not being a mechanical engineer, I probably wouldn’t even know what features I’m missing!

photo collage of 3D printed "Kettős Kereszt" painted in the colours of the Hungarian flag

3D printed “Kettős Kereszt” painted in the colours of the Hungarian flag

The program is very intuitive to use. I put a few cubes on the workplane, stretched them out into intersecting rectangular boxes and exported an STL file for printing within minutes. You can see a screenshot of the result above. I also made a version with a hole cut out of the top so you could hang it on a key chain. That turned out to be as easy as putting a cylinder in one of the boxes, stretching it out of the top and bottom box faces and marking it as a “hole” in the model.

After scaling the model down to 30% so it fits on my print bed, the final print came out as shown in this photo. It took less than 10 minutes to print at 30% in-fill and seems pretty rigid. I’ve painted on the red, white and green of the Hungarian flag and will hang this up somewhere, who knows, maybe it’ll even be good for a Christmas decoration. If you’d like to print your own Hungarian cross you can download both of my STL files here:

In honour of the heroes! Tisztelet a hősöknek!

Automatically Pop Up Steam Key

Now that I’ve got steam, I get to be constantly pestered by e-mails sending me keys with which to identify that I am myself. To save a few steps in this annoying, repetitive process I wrote a tiny bash script which finds the key in an e-mail from steam and uses zenity to pop it up on my screen, then added a filter in Evolution Mail to mark these “steam verification” messages as read and pipe them to the pop-up script. This allows me to copy the key with a double-click and paste it into steam with a middle-click, without having to poke around in my mail client for the e-mail and the place where the key is mentioned in it.

In the hope that it saves someone else from this irksomeness, here’s the code for the script:


# Displays a pop-up showing a Steam activation key piped to it by a MUA.
# In the e-mail the steam key is wrapped in <h2> tags
# Author: Sion Le Roux <sinisterstuf@gmail.com>

# read e-mail from pipe
while read -r line; do
    # find <h2>
    buffer=$(echo $line | grep 'h2')
    if [[ ! -z $buffer ]]; then
        #strip surrounding <h2> tags
        steamkey=$(echo $buffer | sed -e 's/<\/\?h2>//g')

# display the steam code in a pop-up
zenity --info --title="Steam Key" \
    --window-icon="/usr/share/pixmaps/steam.png" \

Civilian ft. sinisterstuf — Venom

My brother (Civilian) and I recently recorded this rap song, Venom, which you can listen to on soundcloud. We also made a music video which you can watch below or on youtube. This is the first song + music video we’ve released to the public and we’re trying to promote it as much as possible, I hope you enjoy it and will support us in this!

You can download the music video in MP4 format ➡Venom (Music Video) and the audio track in OGG format ➡Venom (Audio Track). Both downloads are available for free!

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Checking Computer Specs in Linux

Note: automated script downloadable at the bottom of this post!

Something you always want to do on a computer, even if only once, is to check its hardware specifications, that is:

  • how much RAM do I have?
  • how much hard disk space do I have?
  • how “fast” is my CPU?
  • how much RAM does my graphics card have?

Of course most modern GNU/Linux desktop environments like Ubuntu usually come with some kind of graphical tool to find this information. GNOME’s System Monitor program should provide at least some of what you’re looking for. The information here is more for when you’re staring at a blinking cursor on a black screen trying to remember what the command was to show information about the CPU, RAM or Graphics Card.

This is the third time I’ve had to go on an internet search quest to remind myself how to do this in a Linux terminal. To save myself the trouble in the future, I’m writing down the commands here and if anyone else finds it useful then that’s great, and a second bird is figuratively killed!
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My brother’s doing his International Baccalaureate Diploma right now and for one of his Geography assignments he had to make these graphs -cross sections of rivers- he called them geographs because… they’re for geography and because it has fewer words, so that’s what I’ll call them here. He drew them by hand but they got smudged and I thought it would be nice if he could make them digitally, but that’s a lot of work. I then thought it would be good if there was an easy way to do this, and, having found one, I’ve decided to share it with the world so that other IB students can benefit from this too!

What is a GeoGraph?

It’s a bunch of points on a graph that shows the depth at different points of a river the class studies.

A graph looks like this one:

Example GeoGraph

Example GeoGraph

And as I understand, it works like this:

  1. there is one graph for each transect measured at different points on the river
  2. the width of the transect is shown
  3. the width of the graph is scaled to the width of the transect
  4. the depth of the river is shown for different points along these transects
  5. the depth is measured at 5 points along the transect:
    1. at the start of the transect
    2. at the end of the transect
    3. halfway between the start and the end
    4. halfway between the midpoint and the start
    5. halfway between the midpoint and the end
  6. the depth is measured as a negative number
  7. because depth is negative the graph is drawn below the x-axis
  8. the graph is shown as an irregular polygon connecting all points on the graph
  9. there is a line along the bottom of the polygon connecting the first and last points
  10. this line is as low as the lowest point on the graph

That’s a lot of points to consider, and it’s why this graph is not easily done using the graphing functions of your spreadsheet application (for most of you that’s probably MS Excel). A lot of people might get frustrated, or resort to just drawing it in Paint or some other simple drawing program, which is much too much work! Don’t worry there’s a much easier way of doing it, and it’s all described below. Continue reading