Harmonographs Generate Geometric Images Unique as Fingerprints

When my elder brother and I were kids back in the late 1970’s, our hacker Dad showed us this 1960-61 catalog of the Atlas Lighting Co (later Thorn Lighting) with an interesting graphic design on the cover. He told us to do a thought experiment, asking us to figure out how it would be possible to have a machine that would draw the design on that catalog cover.

Incorrectly, our first thought was that the design was created with a Spirograph. A spirograph has two main parts: a large ring with gear teeth on the inside and outside circumferences and a set of smaller, toothed wheels with holes in them for inserting a drawing instrument — usually a ball point pen. You hold the big ring, insert the pen in the smaller wheel, and then mesh and rotate the smaller wheel around the big ring. But spirographs can’t be used to draw irregular, asymmetrical figures. You could always recreate a design. Because of the nature of gears, none of them were unique, one off, designs.

A spirograph set like this cannot make the image above[Image credit: Multicherry CC-BY-SA 3.0]
A spirograph set like this cannot make the image above [Image credit: Multicherry CC-BY-SA 3.0]
We figured adding some lever arms, and additional geared wheels (compound gears) could achieve the desired result. It turns out that such a machine is called a Cycloid Drawing Machine. But even with this kind of machine, it was possible to replicate a design as often as required. You would fix the gears and levers and draw a design. If the settings are not disturbed, you can make another copy. Here’s a video of a motorized version of the cycloid machine.

The eventual answer for making such designs was to use a contraption called as the harmonograph. The harmonograph is unique in the sense that while you can make similar looking designs, it would be practically impossible to exactly replicate them — no two will be exactly the same. This thought experiment eventually led to my brother building his own harmonograph. This was way back when the only internet we had was the Library, which was all the way across town and not convenient to pop in on a whim and fancy. This limited our access to information about the device, but eventually, after a couple of months, the project was complete.

Continue reading “Harmonographs Generate Geometric Images Unique as Fingerprints”

Hackaday Links: December 14, 2014

 

The Progressive Snapshot is a small device that plugs into the ODB-II port on your car, figures out how terrible of a driver you are, and sends that data to Progressive servers so a discount (or increase) can be applied to your car insurance policy. [Jared] wondered what was inside this little device, so he did a teardown. There’s an Atmel ARM in there along with a SIM card. Anyone else want to have a go at reverse engineering this thing from a few pictures?

[Alex]’s dad received a special gift for his company’s 50th anniversary – a Zippo Ziplight. Basically, its a flashlight stuffed into the metal Zippo lighter we all know and love. The problem is, it’s battery-powered, and Zippo doesn’t make them any more. It also uses AAAA batteries. Yes, four As. No problem, because you can take apart a 9V and get six of them.

‘Tis the season to decorate things, I guess, and here’s a Hackaday snowflake. That’s from [Benjamin Gray], someone who really knows his way around a laser cutter.

HHaviing trouble wiith a debounce ciircut? HHer’s a calculator for just thhat problem. Put iin the logiic hhiigh voltage level, the bounce tiime, and the fiinal voltage, and you get the capaciitor value and resiistor value.

A harmonograph is a device that puts a pen on a pendulum, drawing out complex curves that even a spirograph would find impressive. [Matt] wanted to make some harmonographs, but a CNC and a printing press got in the way. He’s actually making some interesting prints that would be difficult if not impossible to make with a traditional harmonograph – [Matt] can control the depth and width of the cut, making for some interesting patterns.

The Mooltipass, the Developed On Hackaday offline password keeper, has had an interesting crowdfunding campaign and now it’s completely funded. The person who tipped it over was [Shad Van Den Hul]. Go him. There’s still two days left in the campaign, so now’s the time if you want one.

Three pendulum harmonograph

Just the other day we were thinking “You know what we need more of around here? Harmonographs!” And our requests were answered when [Paul] sent in his three pendulum harmonograph. For those unaware, it’s a mechanical device that draws Lissajous curves or “really cool circles” to quote some of our staff.

[Paul] includes all the plans necessary to make your own harmonograph and begin drawing today. If you can’t wait, there’s a video of the three pendulum harmonograph etching a masterpiece after the jump. Continue reading “Three pendulum harmonograph”