Rose plots

source by Dan Anderson:
Enlarged and plotted on a Roland DXY pen plotter: 0.7 mm black pen on design vellum.

Full page:

Even if the 0.7 mm pen is a bit chunky for fine guilloché effects, the plotter output is pretty crisp. Here’s a detail at full resolution:

select this to see the full resolution scan. Original is just under 6 cm wide

Unfortunately, an earlier attempt to print this figure using a fresh-out-the-box 20+-year-old HP SurePlot ¼ mm pen on glossy drafting paper resulted in holes in the paper and an irreparably gummed-up pen. If anyone knows how to unblock these pens, I’m all ears …

birb chirper v2.0

This is one of those toys that you whirl around on a piece of string and it makes a chirping sound like a flock of sparrows. I have no idea what they’re called, so I called it birb_chirper.

Print Settings

Printer: Reach 3D
Rafts: Doesn’t Matter
Supports: Doesn’t Matter
Resolution: 0.3 mm
Infill: 0%

Notes: This is a thin-walled model, so use at least two shells and no infill for smooth walls.


Take a piece of thin string about 1 metre long (I used micro-cord, very fine paracord), pass it through the hole in the tip, then tie off a jam knot that’s big enough to stop in the hole in the top but still pass back through the slot in the side. Now whirl the thing around fast by the string, and it should start to chirp.

This is intended for the amusement of small children and the annoyance of adults.

How I Designed This

The tip of this thing is an ogee curve. I’ve included my library for creating simple ogee and ogive profiles in OpenSCAD.

// ogive-ogee example
// scruss, 2018
use <ogive_and_ogee.scad>;
ogive(20, 35);
translate([0, -5])text("ogive(20,35)", size=3);
translate([30, 0])ogee(20, 35);
translate([30, -5])text("ogee(20,35)", size=3);

Download: Thingiverse —birb_chirper by scruss. Local copy:

western electric marbling

accidental marbling found in injection-moulded recycled plastic microphone cup in a 1984 Western Electric 2702 (Princess) telephone handset

When you fix a thing and it just works …

When you fix a thing and it just works …

When you fix a thing and it just works …
Skelf is a Scots word for splinter or shard and is a weak pun on the Stealth clips that splintered for me.

When both clips broke within a week on my Timbuk2 messenger bag, I knew I had to do something. This coincided with me fixing my 3d printer (it was the extruder feed: it was too loose all along!), so I was able to prototype a new clip.

clip section

The files are on Thingiverse: Messenger Bag Replacement 25 mm Webbing Clip, or there’s a local copy here:

Plotting a card …

I made this two-colour plotted card for the MeFi “holiday card exchange – v.e.” thing. Pen plotter is a Roland DG DXY-1300 (1990s) using Roland 0.3 mm fibre-tip pens. Plot size is 123 × 91 mm, and is driven entirely from Inkscape 0.92.

Building (but not necessarily running) Amiberry on Raspberry Pi 3

I might not have Amiberry — an optimized Amiga emulator for Raspberry Pi — running quite yet, but the build instructions at midwan/amiberry are a bit lacking. If you want to compile it under Raspbian Stretch, you’ll need the following packages:
sudo apt install libsdl2-dev libxml2-dev libxml2-utils libsdl2-ttf-dev libsdl2-image-dev
This will at least allow you to get it to build correctly with:
make -j2 PLATFORM=rpi3-sdl2-dispmanx
More later when/if I get it working.

CP/M 3.1 manuals as PDF

The Unofficial CP/M Web site uses some very old file formats. As almost no-one can easily run Amí 3 to read the manuals these days, here are the CP/M 3.1 manuals from that site converted to PDF: