Shortly after finishing my Magnetic Rubik's Dice Cube, I began to think about the prospect of creating a 2x2 version of the dice cube.
First of all, some terminology of the cube that you need to know. A "cubie" refers to any one of the small sub-cubes that makes up the entire cube. A center is a cubie that has only one visible face. it's color or number determines what that side will be, because a center cannot be moved to another side. Edges have 2 visible faces, and are positioned betwixt the centers. Corners have 3 visible faces, and each touches 3 of the edges.
A standard 2x2(x2) Rubik's Cube is essentially a 3x3(x3) cube, but lacking the centers and edge pieces. This presents a problem for creating a magnetic 2x2 cube in the same manner as in my dice cube and gfixler's magnetic cube. In a 3x3 cube, the corners always touch edges. Therefore it was possible to use identical polarities for all internal sides of the corners, as long as all the edges had opposite polarities. In the 2x2 cube, corners touch directly to other corners. No matter what system of polarities you used, there would be some situations that would make the cube unstable or explode.
So I scrapped the idea, until I realized that I could embed a steel ball inside the cube, to which each cubie would attach via a single magnet. The ball would not be a magnet, but rather just a steel ball or ball bearing. Half of the cubies' magnets have one polarity, and the other half the opposite, so that no matter how the magnets are arranged, they will always be relatively stable.
This cube feels very similar to a real cube, albeit quite a bit heavier. The cubies do not snap into position after being turned, as in the 3x3 magnetic cube, since their attraction is mostly to the core rather than each other. Therefore, it's remarkably like a standard 2x2 cube, but that it's translucent and will fall apart more easily (more easily than a 3x3 dicecube too--because it has less than 1/10th as many magnets).
I consider the dicecube (both 3v3 and 2x2) as more of a novelty item than something you would want to use every day, so I don't mind that it's not particularly stable.
Step 1: Get the Materials
- 8 3/4 inch or 19mm Dice (10 recommended)
- 8 R424 ring magnets (I bought a pack of 25, again because of shipping)
- 1 NSBA 5/8" diameter steel ball (Since they are only $.60, get a few in case one is lost)
- High Strength Glue or Epoxy (transparent or translucent)
- Scrap wood (oak or some other hard wood)
- Wood glue
- Optional: Wood screws
- Optional: Silicone Spray Lubricant
- Drill Press
- Dremel or other rotary tool
- 3/4" sanding drum for rotary tool
- 17/64" split point drill bit
- Belt or disk sander (or sandpaper & elbow grease)
- Utility knife
Step 2: Create the Jig
The magnets embedded in each die have to be facing towards the core. This means that we need to drill a hole along one of the cube's four diagonals. Drill presses are usually not designed to do this, so we need a jig, which will hold the die at the proper angle. I came up with numerous ideas for this jig, some of them very complex, involving copper foil, solder, washers, and aluminum channel stock. But I decided that an all wood jig would be cheapest, and easiest to build.
First find a board to use as a base. It should be about the size of your drill press table. Next find a small wood block about 1 by 1 by 2 inches. I recommend a hardwood such as Oak. Use some kind of sander to shave off a fifty-five (55) degree angle from one of the long sides. The easiest way to do this without a disk sander is to mark off the block with a pencil. You can use trigonometry to calculate the dimensions. See the second picture for details. The angle shouldn't go all the way to the bottom of the block. This will lift the die off the base. After you have a 55 degree angle, cut the block into 3 pieces so that each is fairly narrow and has one angled side.
Arrange the slices on the base so that the angled sides face inward (towards each other). If your slices are too wide, you will have to sand them down on the angled end. Place a die in the depression created by the angled sides, and adjust the blocks so that the die fits perfectly. Mark the positions of the blocks on the base with a pencil, then glue them one at a time to the base. When the glue dries, the base is complete. You may want to reinforce the glue with a screw, but be careful not to split the wood.
Step 3: Drill & Grind the Dice
Start by arranging the dice as you want them to be in the finished cube. On each die, there will be one corner that is completely inside the cube. This is the corner that you need to drill from. The press works best when it has a perpendicular surface to drill into, so this corner needs to be sanded down some before drilling the hole. Use some kind of sander that doesn't move too fast--you don't want to melt the die. I used a simple sanding block, while resting the die in the jig.
When you have the drilling surface prepared on all the dice, attach masking tape to the 17/64" drill bit 5/8" from the tip of the bit. You need to drill at least 3/8 inch into the cube, but less than 7/8 inch. Therefore 5/8 inch should be about right.
After drilling the initial hole, you need to carve out the rest of the cube where the steel ball will be. For this I recommend a Dremel tool. Each die needs to have a quarter-sphere carved out of it. The sphere should have a radius of just slightly more than 5/16 inch. I used a 3/4" sanding wheel for this, and touching up with a steel grinding bit. I used a steel ball to check my work and make any adjustments necessary.
After this, the holes need to be deepened so that the magnets rest at just the right height. Once again, this is mostly guess-and-check. Place magnets in the holes and attach the core. If the dice don't touch each other, one or more holes need to be deepened.
IMPORTANT NOTEThe drill press is an amazing machine, but it can also be extremely dangerous if not respected. I held the dice in the jig with my hands, as you can see in the picture, however I have a good deal of experience with the press. If you aren't very familiar with using a drill press, or don't feel completely comfortable holding the dice with your hands, you may want to modify or add to the jig so that it holds the dice for you. below is a copy of some of the comments from the intro page regarding the safety of this step.
RE: Holding down the dice with your fingers whilst drilling - be very careful, this is a daring way to use a press. One inclination might be to wear gloves, but this can be a problem in that the bit could catch on the glove (which is even closer to the bit while holding such a small object than a gloveless hand would be) and then your hand is pulled along for the ride. A more elaborate jig might be the conservative route to take.
Another option would be to take the jig, screwed together not just glued, and put it in a pan you fill with water up almost to the tip of the cube and freeze. Drill while it's suspened in the ice, and the ice will result in the plastic being colder so the bit cuts cleaner too.
You make a good point, one that I probably should have spent more time talking about in the instructable, other than the comment on one of the pictures. One problem I see with freezing the dice is that the friction of drilling tends to create a lot of heat, which I would think might melt the ice around the die rather quickly. Some of my original ideas included a round washer with a hole large enough for the bit to fit through easily, yet small enough to catch the edges of the die. then wires would be attached somehow to the washer, which would go through the base and attach to weights or tensioned springs.
In the end however, I decided that since the plastic is pretty soft, my hand pretty steady, and the press fairly slow, I'd try it without the complicated washer setup.
On a final note, although I never had any problems with losing control of the dice, if you do happen to, get your hands away from the work area and turn off the press.
Unless the drill bit is incredibly dull, there is no problem melting the ice just to get a hole of suitable size. A hunk of plastic is a reasonable insulator, and a large block of ice doesn't melt very fast. It only needs to hold it still for about 5 seconds if that and the drilling can actually go faster when you're not having to be particularlly careful of your fingers.
We can think through lots of ways to do it, but generally speaking you may have more skill or experience with a drill press than some and I'd hate to hear someone had their finger harmed. It's easy to get too relaxed using a drill press and to forget just how powerful it is. Suppose somehow the bit caught on your finger, it can easily force the entire hand up to the top of the bit and that's going to be startling enough that you won't be able to so quickly turn the press off, and turning it off doesn't apply any kind of braking on most presses. IMO, safety first.
I'm still not sure about the ice method, but then i've never tried that technique before. I agree wholly about the safety aspect, and that I should have focused more on it.
Step 4: Glue the Magnets
At first, to glue the magnets, I attached four magnets to the steel ball, two with opposite polarities to the other two. Then I added some glue to the holes of four dice, and placed one of the magnets on the ball into the hole of each die. But I soon found out that this technique doesn't really work that well. It's best to just put some glue (not too much) in each hole, and then shove a magnet in it, making sure it's all the way down. If the magnet looks like it's riding too high, you may have to take it out and redrill the hole a little deeper (after the glue dries). You also should make sure that four of the magnets have the opposite polarity of the other four, but it really doesn't matter which is which.
That's it for this step. If you've already made a 3x3 cube, you will be telling yourself "gosh that was easy" right now.
Step 5: Put It All Together
To wrap it all up, put all the dice together around the steel ball and try rotating it a few times. It should rotate fairly freely. You may be able to ease the action a bit by applying silicone spray or "cube lube" to the internal faces, magnets, and steel ball.
If it doesn't seem to want to stay squared up without all the pieces in, don't worry; once all the pieces are in place, it should square up all by itself.
2x2 cubies are usually a bit more than 3/4" if I remember correctly, so the 2x2 dicecube is going to feel a little small, but not uncomfortably so.
Now go make some 2x2 cubes and tell me about your experiences!