Intro: Magnetic "Fire Ants" Moving Sculpture
Want to make something completely impractical but super cool? Here's an idea. "Fire Ants" Is a Kinetic Sculpture that I created in early 2016.
The freaky ant-like creature motion is created through a nearby changing magnetic field that is generated by large ferrite magnets rotating inside the glass dome (more on that in the next step).
This Instructable explains how it works, where to get the parts, and gives you general guidance on how to make one of your own! Some of the details around motor/base mounting can be solved a number of different ways depending on the scale and shape of your sphere and size of your "ants" and inner magnets, etc so those details are left to your own creative customization. This Instructable will give you the basic component-level steps needed.
Step 1: Components You'll Need
Disclaimer: These links are provided as a general guide for what to buy, not as an advertisement for the vendor, etc.
- Geared motor (capable of at least 5V) running roughly 60 RPM
- 5V motor speed controller (low current) ++
- Round glass desert plant terrarium (roughly 12cm in diameter)
- ~20 4mm magnetic ferrite beads*
- 100 6mm magnetic ferrite beads*
- Two large 25mm ferrite spheres*
- Silicone wire, 30 gauge
- Small hot glue gun + sticks
++Possible to order one with a higher voltage rating, just don't drive the motor above it's maximum rating!
*This ceramic magnetic material type is often searchable as "hematite" or "magnetite" but it's rarely made from natural magnetic hematite these days.
Step 2: How It Works
The motion of the Fire Ants is created by small gear motor which rotates two large ferrite magnet balls underneath a glass terrarium. The ant-like motion of the red wire and smaller magnets is due to the force of magnetic torque that large inner ferrite magnets play on the outer smaller magnets that are attached to the glass terrarium. The smaller magnetic beads are secured into place on the glass terrarium with small gauge red silicone wire, which gives the ants an unpredictable "jiggle" like kinetic behavior. This kind of special kinetic motion would not be as good if ordinary vinyl coated wire were used in place of silicone wire. Additional bits of the 4mm magnets are sporadically attached to the larger 6mm magnets for additional anthropomorphic effect.
Step 3: Putting the "Fire" in Your Ants
The "Fire" aspect of this sculpture comes from interweaving silicone wire through the magnetic beads as shown.
Cut the silicone wire into roughly 3 inch segments and feed it through the holes of the magnetic 6mm and 4mm magnetic beads and tie off them as shown in the picture above. You're going to be cutting and tying a LOT of these, so get comfortable... The wire of the 6mm beads will be what you attach to the glass base. The 4mm beads will loosely (naturally) attach to some of the 6mm beads once you begin to tune the sculptural behavior (more on that in the final steps).
Step 4: Attaching Silicone Wires to the Glass Dome
You now want to attach the two ends of your silicone wire that are tied through the 6mm beads to your glass dome using very small dabs of hot glue***. When gluing, take care to space the beads apart so that they are not too close together as they will just attach together and not be affected as well by the nearby magnetic field that is created from the rotation of the larger ferrite magnets. It will take some time and effort to develop a technique in attaching these silicone wires without making a mess so be patient with it, and maybe even practice on another scrap glass piece that you have lying around.
*** I needed a find a glue that both dried quickly, clearly (or at least clear enough to look good) and adhered to both silicone wire and glass. Not a lot of glues do well with this material combination let alone adding the requirement of drying instantly and clearly, but luckily I didn't need very really strong adhesion for this piece. For my first revision of this, I initially tried using super glue to attach the silicone rubber wire to the glass sphere. This proved to be a real headache and didn't looked terrible due to a number of factors. Hot glue does the job surprisingly well all factors considered.
Step 5: Tuning the Sculptural Look and Kinetic Behavior
Once all your wire attachments are glued in place, you then will want to begin testing and tuning the distance and orientation of the inner rotating magnets within the glass dome. Two factors that are important in creating the best natural motion are:
1) Distance between the rotating edge of the large spheres and the glass dome.
Generally speaking, you are going to want to have your large ferrite spheres at a distance less than 1 inch away from the glass dome. Magnets that are further away than that will likely not effect the smaller magnets strongly enough to produce interesting movements. Position the motor such that two magnets are rotating at an even distance between the outer edge of the glass in all directions and the outer edge of the magnetic sphere.
2) Magnetic orientation of the large ferrite magnets.
Use hot glue to glue the large ferrite balls to the flat strip of material connected to the rotating rod. Orient the magnets such their north/south poles are NOT well aligned with one another, as shown in the diagram. This will create the most chaotic and random behavior of the magnets around the glass dome.
Step 6: More Customization Tips in Sizing and Positioning of Rotating Magnets Within the Dome
As a general rule, you will want the length of the connecting pole between the motor and the bar holding the magnets to be longer than half the diameter length of the glass dome, so that your can bury the motor a stand that is more aesthetically pleasing. I created an aluminum pole that was 7cm long by drilling a center hole with a lathe, glue and then running long M4 screw that ran down the column attaching to the motor. I then attached a flat brass strip 50mm long across the top of the aluminum pole with a dab of hot glue.
After I had the motor rotor created, I then buried the base of the motor into a stand by drilling a cylindrical hole out of the center of a 15cm circular wood base and gluing the motor in place.