Today a product was listed on Kickstarter that has the tech world drooling. Since you are reading this post I'll assume you know all about the Hendo Hoverboard from a PR/marketing standpoint. What is missing from all of these articles is a good explanation of what exactly is powering this amazing device.

As a disclaimer, I have no affiliation with the company and have no real insight into the inner workings of the device. I am also not a physicist, so my explanation of the architecture will be very crude.

The basics

The Kickstarter page gives some basic insight into what makes this magic possible.

Lenz’s law explains how eddy currents are created when magnets are moved relative to a conductive material. These eddy currents in turn create an opposing magnetic field in the conductor. Our core technology, which we call Magnetic Field Architecture (MFA™), focuses this field more efficiently.

I have only recently become aware of this phenomena through MIT ope courseware and some Youtube videos. Here is a demonstration of the effect using spherical neodymium magnets and a copper pipe:

The basic principle is that when a magnetic field is moved relative to conductor, it induces a current in the conductor. This occurs even if the conductor is non-ferromagnetic (i.e. a magnet won't stick to it). Since a current flowing through a conductor also produces a magnetic field, the conductor will emit it's own magnetic field but only while the magnet is moving. The magnet's field and the conductor's field now interact in much the same way as two magnets do.


So how do you use Lenz's law to levitate something? Just move high power magnets over the surface of a non-ferromagnetic surface like aluminum, copper, silver, or even gold. I found a great example of this technique from way back in 2009:

In the video, Scott Stevenson explains that the neodymium magnets are placed with alternating poles. This is responsible for the repulsion felt by the disk.

I understand it this way. As a magnet is rotating over the conductors surface, it induces a sympathetic magnetic field that would attract the magnet. Then the magnet rotates away and the next magnet, with the opposite pole, passes over the surface. This repels the magnet for a brief time, until the movment of the magnet reverses the direction of the current and creates the opposite field, attracting this new magnet. Then the cycle repeats. Again, I am not a physicist, so take this with a grain of salt.

Now make me a hoverboard

In the comments for Scott Stevenson's video a user quickly recognized the potential of this technique:


Ironically, this comment received only 1 upvote...

I'm not sure if this very public disclosure of a potential use for this technology will interfere with Arx Pax, LLC's patent endeavors, but it gives me hope that at least some of this technology will remain unpatentable.

So how does the Hendo hover so steadily? I have some experience tinkering with quadcopters, so I immediately recognized the 4 motor configuration.
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Even the small "Developer Kit" called the Whitebox has this 4-hover-engine design.
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With spinning disks in each motor unit, the board must use counter-rotating engines to negate the torque of the motors.

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As with quadcopters, varying the spinning of these disks allows you to rotate the body.

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There is also the issue of lateral movement demonstrated in the Kickstarter video by the Roomba-like robots. This could be achieved by slowing the engines on the side of the target direction, but I didn't notice any tilt as the robots moved and changed direction. So I believe this is actually achieved by rotating the spinning disk slightly and pushing off the surface at an angle.

So it's not magic?

So there you have it. Its not hard to understand and apparently is not hard to implement. So what does one do with an idea like this? The Kickstarter page tells us:

He labeled this epiphany: Magnetic Field Architecture (MFA™). Then he trademarked and patented the hell out of the idea.

It seems like the main concern for Gregg Henderson's company was applying for patents (US20140265690, US8777519).

While I love the idea that I will one day finally get my hover car, I can’t help but feel like there won’t be any more innovation in this field until the patents run out (think Segway).

But individuals tinkering with hardware don’t have to worry themselves with patent infringement. So, I hope to see some even more amazing uses of this technology by the maker community very soon.