Nuclear Models: How to Build Them

Copyright 1997 by Arnold J. Barzydlo

Over the years I've refined my modeling techniques quite a bit. The first models were done on balloons and ping pong balls, but it was difficult to draw the geometry accurately, and making measurements of the crude results was pointless. When I eventually started building wire-frame models, things changed. This web site is designed to help you build copies of these nuclear models. You will need certain materials:

2-Low Temp Hot-Melt Glue Guns (craft store, about $4.00 each)
Colored Glue Sticks (two colors are sufficient, craft stores)
22 gauge Solid Wire (3 or 4 distinct Colors, electronics parts distributor)
Engineer's Ruler (triangular type with a "20" scale, art supply store)
Freeze Spray (available from electronics stores, use sparingly, its expensive)
1/8 inch Clear Heat Shrinkable Tubing (also from electronics stores in 6 foot lengths)
Fine Point permanent ink marker (supermarket)
Carpet thread (department store)
Wire Cutters (electronics or hardware store)
Christmas Ornament Hooks or Wire Paper Clips (Don't use your wire cutters on them!)
Lighter, alchohol burner or heat gun (for shrinking the tubing and smoothing out hot glue)
Parental Supervision if you are not an adult!

First, cut the wires to the proper length, 1/2 the length given for each loop value (L1, L2, etc...). (See the note below.) After cutting them you may wish to mark the wires at points 1/2, 1/3, 1/4, or 1/6th of their length. Study the photo and number of snap points for the loop to determine where to place your marks. Most of the models have large loops which need to be marked at half the wire length. The joined ends of the wire will represent one of the marks. By marking snap points on the wires before assembling them it helps to insure your models will look right and not be all lopsided when you're finished. It is usually not necessary to mark the smaller loops, as long as you make them round and cut them to the right length, they should be easy to fit symmetrically to the core structure (providing the core structure isn't all lopsided.) There will be some error in the models introduced by the diameter of the 22 gauge wires, so be expecting the small loops to be just slightly undersized in most cases, because the equations do not account for the cumulative error in the wire diameter. The strings in the nucleus actually intersect, and so do not suffer this error, but its impractical to intersect solid wires, so we have to settle for an approximation. There are only one or two steps requiring the use of an open flame. When forming the wire into loops, the ends of the wire are joined by slipping 1/4 to 1/2 inch of shrink tubing over the ends and heating it until it tightly grips the wire (try not to burn the wire insulation). The loop equation associated with each model tells you in advance how many loops of what size you will need.

Note: The loop equations were written for classroom demonstration models made with 18 gauge wire at twice the size of the models in the photographs. Use the "20" scale on an Engineer's rule to scale the models by 1/2 for 22 gauge wire. Otherwise they'll be too big and floppy.

After making the loops for a model, study the photo's and start gluing them together at their snap points. Use the Freeze Spray to quickly set the hot-melt glue where you have tacked the loops together. After tacking the wires in place with hot-melt, you will want to anchor them by working a small amount of hot-melt around each wire crossing until it is completely wrapped in glue. If you know which type of quark it is, you may color code it with colored hot-melt at this point, or you can wait until the model is finished and color code the quarks with a final layer of colored hot-melt. (If you don't have colored glue sticks, I find it works just as well to cut out small circles from colored construction paper and glue them to the models with hot-melt. You can even label them "Up" and "Down" if you want.) Pull off the glue strings (you know, those annoying cobwebs that the glue gun strings all over the place) and warm the glue blobs briefly to smooth their surfaces and melt the "cobwebs." (Don't touch or set the model down while the glue blobs are still hot! Use the freeze spray if in doubt! Otherwise you may glue it to yourself or the table!) Save pinning radical strings (P.V.B.'s) until last, they can pin to any Up quark, but if you do it now, you won't be able to change them.

Advanced modelers may wish to glue actual snap fasteners to the Up quarks so they can detach and move pinned strings from one Up quark to another. I have cut small squares from "Superlock Fasteners" (Radio Shack #64-2363) and glued them to the Up quarks on the P5 shell so I could move the radical strings around. It takes a bit of trial and error to make this technique work, you must remove the sticky backing from the superlock squares and glue them so the hot melt glue overlaps the top edge of the superlock square slightly. (Otherwise they pull off too easily.) Also, the squares must be large enough to provide a positive locking action. When removing pinned strings mounted thus, you must carefully "break" them off near the fastener, as if you were breaking a stick. If you just try to pull them straight off, you'll probably wind up bending your model all out of shape. Most radical strings I just glue on, because I need to know at a glance how many there are, not where they are. Chemists will be much more interested in the actual pinning sites, I'm sure. For them, pinning the strings should be done after the proton and neutron shells are stacked, assuming they can generate a computer model to work with. After you're done, attach a piece of carpet thread to the model and tie it to a Christmas ornament hook (or a paper clip bent into a hook). Hang it up on a wire and build another.

Its pretty easy to duplicate the shells I've modelled, and is actually fun once you get going. There are many as yet undiscovered solution sets. If you want a real challenge, study the shell models and the empirical laws I used to model them, then try and find new solution sets. I didn't plan on going past neon with glue-gun and wire modelling techniques, I'm kind of stymied by the rapidly increasing complexity of the models as the quark count goes up. There are probably more rules that I am not yet aware of. I will tell you one important rule... No pre-quarks are allowed! Pre-quarks are intersections of only two strings on the nuclear surface. There must always be at least three string crossings, or none. This should help a lot in eliminating false solution sets. If it turns out that this system of nuclear geometry doesn't work (I'm pretty sure that it does, though), then at least you'll have some really interesting ornaments to hang on your Christmas tree! Have fun.

Chemistry Notes
Key to Nuclear Models
Nuclear Shells
Empirical Laws