This is my 1st attempt to produce an instructable, I'm going to explain you how to build a system to levitate a magnetic top. It seems there is a commercial toy like that and now you'll be able to made it on your own. I've avoided inserting theory inside this instructable, just remember the system is based on magnetism and angular momentum (see also bibliography at the end). The system is sensitive to dimensions and weights and I've wasted a lot of time to reproduce it, so if you want to build it up try to follow my hints, probably you can get the same results with a different model but prepare yourself to be patient.

Step 1: Tools You Need

a) a cutter
b) a drill bit diameter 5.5mm (7/32")
c) a small saw
d) a marking pen (or a pen/pencil)

Tools that can help you but you don't need them
e) a compass
f) a dremel drill
g) a small scale for small weights (max 50g, 0.1g precision)

Step 2: Materials You Need

Except for the neodymium magnet I've tried to use materials that you can find in a good hardware store, they are usually very cheap. What you need are::
a) a neodymium magnet. I've found mine at http://www.supermagnete.it but I think there are many web stores that can provide it. What I've used is the R-27-16-05-N, pay attention the magnet should have the following dims & weight:
- diam: 26.75mm / 16mm or 1"3/64 / 5/8" (ext diam / int. diam the magnet is a toroid)
- tickness: 5mm or 13/64"
- weight: 14g
b) a magnet for the base. That is a bigger toroidal magnet made of ferrite, I've recovered it from a broken loudspeaker. You have to remove some screws from the loudspeaker and then you to have to separate the polar expansions from the magnet, they are glued together. Do not hit or force the magnet, you can break it easily. The best thing to do is to warm up the expansions (with a blowtorch or a propane torch for istance) and then force them with a screwdriver.
- diam: 115mm / 57mm or 4"17/32 / 2"15/64 (ext diam / int. diam the magnet is a toroid)
- tickness: 15mm or 19/32"
- weight: 600g
c) a cork cap
d) a plastic screw
- diam. 6mm or 15/64"
- length 64mm 2"33/64"
e) copper and plastic washers. The external diameter of the washers should be smaller than the external diameter of the neodymium magnet. The weight should be variable between 0.5g to 2g
f) glue for paper, it is usually sold in sticks
g) tape
h) a cardboard box (the one I've used is a shoebox)
i) 10 or more DVD's sleeves
j) a couple of wooden shims (small wedges) and/or some sheets of paper
k) sandpaper

Step 3: Build the Magnetic Top

a) with the cutter cut a slice of cork from the cap. The slice should be 5mm (13/64 ") thicker;
b) put the neodymium magnet on the cork slice, with the pen trace the internal circle of the magnet on the slice;
c) drill the center of the cork slice with the 5.5mm drill bit. You can do it by hand, the cork is very soft;
d) cut the slice on the line tracked at point b);

e) glue the lateral surface of the slice and then insert it inside the neodymium magnet;
f) shorten the plastic screw (remove both top and tail of the screw with the saw). The final length should be 30mm;
g) reduce the weigth of the screw to 0.7g (use the sandpaper and the saw for that), now youhave all the components;
h) put the screw inside the hole previously made. Finally you have the magnetic top.
i) As I told you in the intro the weight is crucial. At the end of the previous steps the weight of the top should be 15g (more or less). That weight is smaller than you need, for this reason you need to glue one or more washers to the magnetic top. The right number of washers and their weight is well explained in the "Levitation step"

Step 4: The Magnetic Trap: Researching the Starting Point

Now you have all you need to start the experiment.

First of all you have to face the surfaces of the magnetic base and top on the right way:
a) put the base on a leveled table;
b) take the the top in your hand keeping it from the shaft;
c) try to push the top into the center hole of the base. If the top is continuosly rejected you have to invert the base. You should feel a little rejection at the begining but if you apply pressure the top will be attracted inside the base, that is the right direction.

Second, the levitation effect is stable only within a small volume, called magnetic trap , over the magnetic base. You can't start spinning the top in that region but you have to start from a lower position called starting point . To find that point:
d) build a couple of small towers using 3 or 4 DVD's sleeves each. The towers should be 40mm high;
e) put the cardboard box on the top of the towers and create a small bridge;
f) slide the magnetic base under the bridge (more or les in the middle);
g) keep the top in your hand (as you've done in point b)) and put it inside the box, try to push the tip of the top to the box base;
h) now you need to find the center of the magnetic base. Probably the top is sliding in every direction but after some attempts (move it around the base of the box) it should be gently attracted from below and it should be stable. You've found the starting point . If you're not able to find that state try to change the bridge's height adding or removing some sleeves. For a fine tuning of the height use some folded paper sheets instead of the sleeves.

Step 5: Levitation

This should be the final step, and you need to stay calm and patient. In this step you'll move the spinning top to the magnetic trap .

Starting from the position found in the previous step you need to spin the top. So try to spin it now. 4 things can happen:
1) the top always tend to stay on the groudn of the box. It is impossible to spin it. The reason is the top is too close to the magnetic base. Raise the bridge acting on the DVD's sleeves (or use the paper sheets for a fine tuning);
2) the top always jumps away and you don't feel the small attraction from below. The bridge is too high, reduce the height of the bridge;
3) you have a mixed behaviour of 1) and 2). In that case you're are in the right way, keep trying until the top spins stably;
4) the top spins stably.

Great now you're able to spin the top for at least some seconds. During that time you have to gently raise the cardboard box to move the top inside the magnetic trap .
3 things can happen:
1) while rising the box the top is gently lifted up but suddenly it falls down. The top is too heavy. Reduce its weight by removing one or more washers;
2) while rising the box the top is lifted up and it jumps away. You need to:
- add some weight to the top using the washers or small pieces of tape (fine tuning)
- tilt the magnetic base using the wooden chips. The magnetic base must be raised on the side where the top is jumped away;
3) after cycling on point 1) and 2) for two or three times you should be able to levitate the top. When you're close to that state the tuning is very fine and you must use small pieces of tape for changing the weight of the top and small shifts of the wooden chips (remember they have a triangular shape so shifting them below the magnet base you can achieve whatever tilt of the base)

Step 6: Bibliography and Videos

[1]http://www.arrigoamadori.com/lezioni/TutorialFisica/MomentoAngolare/MomentoAngolare.htm
[2]http://it.wikipedia.org/wiki/Momento_angolare
[2]http://www.physics.ucla.edu/marty/levitron/node1.html
[3]http://www.levitron.com/physics.html(magnete d
[4]http://digilander.libero.it/scienza_in_gioco/trottololevitante.htm
[5]http://en.wikipedia.org/wiki/Spin_stabilized_magnetic_levitation