The basic parts needed to make a flux capacitor are 8 high voltage capacitors (Vishay Cera-Mite 500 pf 15 KV capacitors with Y5U dielectric are suitable), a powdered iron toroidal inductor core with a permeability of about 20 (an Amidon Associates T130-1 is ideal for frequencies less than 100 KHz while a T106-2 is suitable for higher frequencies), and enough AWG # 22 to wind 650 to 700 turns on the inductor core and capacitors (Belden Polythermaleze wire is ideal because of the high voltage and temperature tolerance of its insulation). Additional parts and supplies you may want are super glue, a strong clear epoxy, some Bondo, a short piece (10 to 12 feet) of AWG # 24 magnet wire, and a medical grade thermistor (like that shown above, available from Digikey).

Assembly starts by sawing the inductor core in half with a small hack saw. Saw with slow strokes as the powdered iron material dulls the blade quickly. This is especially the case for the mu = 10 material (red) shown here. Have several spare blades handy. After the core is sawed in half, a Dremel tool with a small diameter drum sander is used to shape the flat sawed faces to form around the capacitors as shown. Note that notches in the core have to be made to accommodate the leads of the capacitors. The pieces are then clamped in place with small pieces of plastic and small clamps, and the capacitors are tack glued in place between the inductor halves with super glue (not too much). When the super glue is set, with the assembly still clamped, a strong epoxy is then applied to the fitting pieces. Devcon “two ton” epoxy or the equivalent should be used. And after the epoxy has been applied the assembly should be cured for 2 hours or so in a toaster oven set to about 160 degrees Farenheit.

After the epoxy is cured, Bondo can be applied to smooth the capacitor/inductor form. This step can either be done as assembly progresses. Or it can be done once all of the capacitors have been glued in place. The next step is to cut the capacitor/core assembly in half again and repeat the last steps, bringing the capacitor count to four.

The cutting, facing, and gluing procedure is done two more times to bring the total capacitor count to eight, as shown here. More Bondo is applied to smooth the form of the capacitors/core torus. And a small hole can be drilled into one of the inductor core segments to accommodate a thermistor so that the temperature of the device can be monitored during operation.

After shaping with Bondo is complete and the thermistor (white probe with twisted leads) is glued in place, insulation for the capacitor leads is provided. Roughly 5/8 inch lengths of 1/16 inch heat shrink tube is used for this, And two layers of tube are placed on each lead because of the high operating voltages. The assembly is then painted with at least two coats of corona dope or insulating varnish. Then two magnetic flux sense coils (green wire) are wound around two of the capacitors in the assembly so that the magnetic flux in the device during operation can be detected directly.

The next step is to wind the inductor coil The next step is to wind the inductor coil. The wire to be used is wound onto a bobbin about a foot in length. A length of 1/16 inch heat shrink tubing is placed on the end of the wire so that the lead to the inner windings is insulated from the outer windings. Then, for a low frequency device (that is, 75 to 80 KHz when run as a resonant series LC circuit), 650 to 700 turns of wire must be wound. Preferably, this should be done as a single, continuous winding; so make sure there is enough wire on your bobbin when starting. Pads on the inductor must then be applied for the mounting clamp for the completed assembly. This is done in two steps. First, slow curing epoxy is applied where the clamp pads are to be located (to insure some penetration of the windings by the pad bases). When this has been cured, Bondo is applied to make the pads and carefully shaped with a small file, as shown here.

After the pads have been applied, the capacitors are wired as shown After the pads have been applied, the capacitors are wired as shown. The inner plates are wired together, bent toward the center, as they will be the high voltage part of the capacitor circuit. The outer plates, that will run at ground potential, are also wired together. Corona dope (or insulating varnish) is applied to the assembly – especially in the areas around the capacitor leads – for the assembly must be able to withstand several kilovolts without breakdown..

The bare capacitor wires are insulated with E-6000 air cured “plastic rubber”. (Only the inner ring has been treated with E-6000 here.) This is also used to stabilize the field sense coil leads. Sections of two pins of Augat SIP pins make excellent light-duty connectors. Here they have been soldered onto the trimmed ends of the field sense coils.

The device is mounted on the thrust sensor with a single 8-32 stud The device is mounted on the thrust sensor with a single 8-32 stud. It is clamped on that stud with bakelite cross pieces, a spacer, and washers. These parts are shown here.