Step 1: Video Overview
Step 2: Earnshaw's Theorem
So it is impossible to suspend a magnet in space using just bunch of other magnets. But take a look at the video. There is a large ring ceramic magnet and another magnet which is also a top. And if I carefully spin the second magnet above the first one it will indeed hang in the air. How is that possible?! Let’s talk about this and a few other loopholes in the Earnshaw’s Theorem and actually build a few magnetic levitation devices. This is gonna be cool!
Step 3: Bill of Materials
* The large magnet is actually a stack of two 115x45x20mm magnets: http://www.magnet4sale.com/ceramic-magnets-ring/
* The small magnet is taken from a 1.42″ cup magnet. To take a ceramic magnet from the cup I put it in hot water for 20 minutes to loosen the glue, then pried with a screw driver and pulled out like it is shown in the video and explained further in this instructable step #6.
In addition to that I used
* 6.56mm (1/4″) wood dowel from Michaels
* Bunch of rubber and brass (i.e. non-magnetic) washers from Home Depot (Lowes has better selection of rubber washers, Home Depot has more brass ones). In fact for this exact setup I used only one washer with 32mm in diameter and 1.3mm in thickness. All other brass washers were not necessary in the final version.
* Plastic container from your cupboard to cover the large magnet. I used a 68mm tall and 143mm in diameter container #12 (1.5pt) from Rubbermaid.
* Aluminum or plastic (i.e. non-magnetic) sheet from Lowes
* Good electric tape
All in all this setup cost me approximately $30.
Step 4: Plastic Container?! Seriously?!!
Step 5: The Height Does Matter
Step 6: Retrieving the Smaller Magnet
Step 7: Make the Top
If you’re exactly following the specifications from rtfms.com add the rubber washer to make its weight approximately 12.5 grams. Make sure you put a non-magnetic spacer between the top and the scale, otherwise metal parts of the scale will attract the magnet and the measured weight will be inaccurate. See the video for details.
Step 8: Make the Base
Cover the large magnet with the container, put the aluminum sheet on top and your base is ready.
Step 9: Adjust the Orientation and Height of the Base
Put a flat sheet made of non-magnetic material on top of the plastic container and try spinning the top. Good chance it won’t not only levitate but spin as well. Several things could be wrong with it:
* The big magnet is placed upside down. Remove the cover and slowly lower the top on it. If, while lowering the top, you won’t feel anything then it you feel like the top is sitting on a magnetic pillow then it’s the wrong side. Flip the large magnet over. Now the top feels some resistance while you’re lowering it, than the big magnet starts pulling it inside the hole. That’s the right orientation. Put the cover back.
* The top is too high above the big magnet, so big magnet repels it and once you spin it it will fly away instantly. Reduce the distance from the top to the large magnet by lifting the large magnet. Washers and bottle cups will help you to lift the large magnet.
* The top is too low above the big magnet, so big magnet attracts the top too much and gyroscopic force is not enough to keep it straight. In this case it falls and tumbles immediately after you release it. You need to increase the distance between the top and the magnet. You can do it by lifting the plastic container on washers of bottle cups, for instance.
The perfect position for the top is slightly below that point when big magnet stops repelling the top and starts attracting. Adjust the height of the magnet under the plastic container so the top is located exactly at this position when you try to spin it. You can also move the small magnet alone the top stem to fine-tune the setup.
Please note that in this position you might need to push the top down slightly while spinning it. If you find this inconvenient feel free to reduce the distance between the magnets a bit more.
In fact one more thing can go wrong with spinning: the speed.
* If you spin the top too slow it will start precessing too much and fall too quickly
* If you spin the top too fast it will start precessing even faster and fall too.
* Spin the top not too fast and not too slow. In fact start from the slow side and keep increasing the speed until you reach the maximum speed after which the top goes crazy.
Besides just the initial spinning the spin-stabilized magnetic levitation only works at speeds between 1000 and 3000 RPM (revolutions per minute). So spinning the top faster than 3000RPM won’t help to keep it flying longer.
Once you positioned the top properly it should be able to spin stably on sheet. In fact if you are lucky and patient you can position it in a point at which it will self-stabilize itself. Even if you spin it not too well it will will eventually straighten up.
Oh, and one more important thing is where you start spinning - it should happen exactly above the center of the large magnet, otherwise the small magnet will tumble and not spin at all.
* Once you lifted the sheet a bit the top jumps and flies away. This means that the top is too light and gravitation force is not enough to compensate the magnetic repulsion force. Add some weight to the top. Brass washers are the heaviest ones, rubber ones are lighter. You can also sand the washers to adjust their weight.
* You keep lifting the sheet but the top never takes off the sheet. The top is too heavy and magnetic repulsion force is not enough to compensate the gravitation. Remove a washer from the top. If this is the last washer then replace it with the lighter one. If the top won’t take off even without washers at all you will need a stronger set of magnets.
After adding and removing washers to the top you should reach a point when the top takes off the sheet, tries to levitate on top of the magnet but after half a second it flies away. If you notice that it always flies in the same direction, then it’s time for phase 3: leveling.
* The reason the top is flying away always in the same direction is because the magnetic field of the large magnet is net perfectly level. Pretty much like a ball rolls down the hill our top rolls down the magnetic hill. You even can’t make it horizontal with a regular level as the big magnet could be unevenly magnetized. You need to keep adjusting the big magnet level until the top starts flying away in different directions. Also make sure that the big magnet resides on a firm surface like a table. Carpet won’t work as you will need to relevel the magnet too frequently.
The truth is you probably will need to do phase 2 and 3 simultaneously as it it sometimes unclear why the top flies away so fast. It could be both the magnetic field level and the weight.
Again, you can put washers or something else thick and preferrably non-magnetic underneath the large magnet in order to level it. You can even use an Arduino as a shim if you want to involve a microcontroller in this project :)
Step 11: Adjust the Weight
* Keep adding the weight of the top. You need to add small weights to the top. The fine adjustment weights are in fact so small that washers do not work anymore. We’re talking about 0.1g (0.004oz) precision. The best candidate for adjusting the weight is electric tape. Keep sticking small pieces of electric tape until the top stops flying away.
* If at some point top levitates for a few seconds than falls down -- take out a strip, cut it in half and stick one half back.
Using electric tape you can build a top that will levitate for a minute or two. One problem with it is bad aerodynamics of tape strips. Once you figured out the final weight it is probably a good idea to replace the take with a bunch of brass washers. This will increase the flight time to up to 5 minutes (well, 2-3 minutes is a more realistic time).
One more important thing is that the entire top should be very firm. No pieces should be unsecured or wobbly. Use crazy glue if necessary, but make it feel like a one solid piece.
Step 12: Amaze Your Friends!
The fact this type of magnetic levitation is so unstable greatly reduces its usability. Basically besides amazing people you can’t do much with it. In the future instructables I'll explain how to build more practical levitation devices, so vote, follow, like, subscribe and keep DIYing!
If you like this Instructable please check my other instructables. Thank you for reading and watching!