Author and 3D print aficionado Jake von Slatt noticed that during the dry winter months, larger than usual amounts of static electricity were being generated each time he pulled the flat part off his print bed. Having previously designed and built a Wimshurst Influence machine for issue #17 of Make magazine, he decided to explore the possibilities for 3D printing such a machine in light of his surplus of static charge.
This wonderfully named machine is an electrostatic generator, the eponymous creation of the British inventor James Wimshurst (1832–1903). The primary parts of a Wimshurst machine are a set of counter rotating disks with a series of metal strips, a pair of combs for collecting the charge, and neutralizing bars that contact the strips. When the handle on the machine is cranked, the machine begins to create and capture electrostatic charge turning it into available voltage.
Von Slatt provides an apt metaphor for understanding the way the machine works:
“We’re all familiar with the static shocks we receive after getting up from our seat and touching a door knob when the weather is dry. That act of separating your posterior from your chair causes a charge imbalance; a Wimshurst machine is essentially an idealized series of posteriors and chairs endlessly sitting and standing with a pair of collecting combs to gather the charge produced so that something useful may be done with it.”
Thus began von Slatt’s journey to develop his 3D modeling skills in order to 3D print the necessary components.
He began by using Autodesk’s 123D Design software to create the 3D model. He quickly realized that although the software would be perfectly suited to creating models of the individual pieces required to build the machine, that he would be unable to combine all of the pieces into a single file, though he quickly notes he was using an older version of the software and it is quite possible that a newer version would have made this effort possible.
The machine he wanted to create was more than just merely functional. It would also incorporate a Gothic style aesthetic calling to mind the trefoils, y-tracery, and pointed arches of Gothic cathedrals as well as the beauty of the Gothic revival steam engines of the 19th century. Printing the parts in PLA at a 20% fill produced parts that were mechanically serviceable and he was eager to try them out. Unfortunately, they did not produce a spark.
One theory for the difference in function is that the PLA plastic was actually picking up exhaled moisture that caused them to bleed off charge. Building off of this idea, he printed a second set of disks from ABS plastic. Unfortunately, despite his best efforts, von Slatt was never able to coax more than a ½” spark out of the machine, in contrast to the 6” arcs he had generated with his previous non-3D printed versions. Von Slatt further theorized that the filaments within the disks are not aligned in a way that allows them to maximize the distribution of the charge for collection. A further possibility is that their slight porosity continues to collect moisture despite the change in material and therefore does not allow them to accumulate sufficient charge to create the desired arc.
The files for creating the 3D printed Wimshurst machine are available through Thingiverse and von Slatt hopes that the collective intelligence of a community of obsessive 3D printers might lend some improvements to the original design. In the meantime, the object itself is quite attractive and even if it can’t yet produce an arc, it will still be excellent at starting conversations.
What do you think about this spark of imagination? Let us know if you have any ideas on how to produce bigger arcs over at the 3D Printed Wimshurst Machine forum thread at 3DPB.com.