I recently made this design for an endless spinning top using a rotating magnet to create an Eddy current in the spinning top. After some searches i couldn't seem to find anyone else using the same principle for such a device, so i thought i would share my project. This version is still not perfect, but i think it is a good demonstration of the science of induction and magnetism.
The youtube-channel Veritasium has a great video explaining and demonstrating eddy-currents, which i strongly recommend to watch!
Step 1: Step 1: Find a Suitable Motor and Magnet
In order to achieve good result you will need a fast spinning motor. Holding torque and torque at low speed is not necessary as the forces of the opposing magnetic field aren't really introduced until high speed is achieved. I used the motor from a PC-fan, and i found it works great. I cut away everything except the center hub, which includes the motor and the motor driver. These fans usually run on 12 volts, so finding a suitable power source is fairly easy.
Next you will need a strong magnet, anything will do, but the magnets found in hard-drives are perfect for this application. After gluing the magnet to the center of the motor(this is an important step, as a tiny bit of unbalance in weight will introduce a lot of rattling and vibrations at high speed.) you are all done.
Step 2: Step 2: Making the Box
The only thing needed is a fairly thin plate to separate the motor and the spinning top. I laser cut this little box so it could be used as a desk toy. If there is any interest i am happy to upload the dxf.file for the box.
Step 3: Step 3: Spin!
Now comes the fun part. Seeing as the only criteria for the spinning top is that it is conductive, you have a lot of possibilities. Both copper and aluminum work great, iron and steel on the other hand defeats the purpose here. Since they are ferromagnetic they will stick to the magnet, of course they will spin but the effect is not the same.
It is a fun toy and demonstrates the Eddy-current effect in a way where you can really feel it. Turn the motor off and it seems like a normal wooden box, you can take a piece of copper or aluminum to the box and nothing happens, turn it on, and you will feel the copper being dragged out of your hands. Another thing to note is that magnetic polarity is insignificant, so the force is very uniform.
Hope someone finds this interesting, it would be fun to see someone else's take on the idea!