This is a simple experimental jig for winding a 1.5 inch diameter internal grid in a Farnsworth Fusor, a small hobby nuclear fusion device that uses a technique called Inertial Electrostatic Confinement (hence, IEC fusion). This Thing is just for creating the central electrode in the machine. For much more in-depth information about fusors, you will find a community of Fusioneers at http://fusor.net
The internal grid needs to be reasonably spherical, and I found it hard to reliably get that shape without it looking sad. At first I tried winding the electrode using a golf ball, but once it's formed, you can't get the ball out!
This jig solved the problem by having 16 pieces that nest together with an internal track into which the wire is laid, and outer pieces that provide the guide walls to keep the wire in place as it's being wound.
Stainless steel wire can be used, but it's sometimes hard to work with, and it has a lower melting point than tantalum. Tantalum is also very ductile and easy to wind.
The jig is designed to form a sphere made of three circles by weaving two wires.
Note that the two pieces in each print are not the same; one is designed to sit inside the other, so its screw holes are offset. I thickened it along its vertices so it won't nest inside the other, to prevent some confusion.
Print 8 copies of the object and clean them up.
The screw holes are sized to allow a short 4-40 screw to hold each face to its neighbors (12 screws and 12 nuts in total).
Cut two lengths of wire 14 inches long.
Mark their centers.
We'll be following the winding pattern depicted in the last image;
- Place the wires perpendicular to each other with their centers intersecting at one of the corners (let's call it the north pole).
Add a small piece of tape to hold them in place.
Bend all four ends down to the equator.
Pick a spot on the equator to start at. Use needle-nose pliers to carefully bend a 90 degree turn in the wire so it points east along the equator. Move eastward and repeat this for all four wires until all of them stick out from the equator at a tangent.
Now we'll move around the equator going east again. At each intersection, bend the wire 90 degrees down so it points south. Pass it under the wire that is already there, linking them together.
Bend all the wires down toward the south pole.
- Twist them around each other, using the needle-nose pliers to tighten them down so they are tight around the jig at all points.
You can now disassemble the jig faces by unscrewing them.
The pieces will come out from inside the spherical electrode without deforming it if you're careful. You'll find the grid holds its shape fairly well, though it may benefit from spot-welds at the intersections.