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"Magnetic Field Architecture" and the HENDO Hoverboard - *ALMOST* a real hoverboard

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LAN_403

Nucleophobe

Wed Oct 22 2014, 02:23AM

Registered Member #108 Joined: Thu Feb 09 2006, 11:44PM
Location: Billings, MT
Posts: 61

2Spoons wrote ...

At 40W/kg, levitating an 80kg person on the board will take 3.2kW. Thats going to be one hell of a battery pack if you want more than a few minutes ride time.
Hovering a little box - ok. Hovering a person on something the size of a skateboard? - i'm a little skeptical.

They only claim about a 10-minute ride per charge, so if they have about a 500-1000Wh battery that would make sense (extra watts for the added weight of the board and battery).

A lead-acid car battery has around 1kWh and Li-ion batteries have higher specific energy (100 - 200Wh/kg).

Not sure what room there is for improvement though.

Conundrum

Wed Oct 22 2014, 06:38AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Using superconducting wire would reduce current usage substantially.
Most of the losses are resistive in the coils so 10% less loss = 10% cooler.
Also one improvement I came up with is to use switched coils so they never heat one small area too much, and spread out the field over about a square meter of copper surface to both increase lift capacity and increase system efficiency.

Shame there isn't a way to make any surface briefly conductive, maybe something that filters out argon from the air, sprays it onto the surface and applies a transverse RF field to form a glow discharge plasma which then acts as a pseudo-conductive surface?
Great Scott!
(scuttles off to Patent Office..)

Patrick

Wed Oct 22 2014, 07:06AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Conundrum wrote ...

Shame there isn't a way to make any surface briefly conductive, maybe something that filters out argon from the air, sprays it onto the surface and applies a transverse RF field to form a glow discharge plasma which then acts as a pseudo-conductive surface?
Great Scott!
(scuttles off to Patent Office..)

No, No, stupid... what you really need is neutrino polarized di-lithum yttria film. Duh.

dexter

Wed Oct 22 2014, 08:37AM

Registered Member #42796 Joined: Mon Jan 13 2014, 06:34PM
Location:
Posts: 195

Conundrum wrote ...

Using superconducting wire would reduce current usage substantially.

Also one improvement I came up with is to use switched coils so they never heat one small area too much, and spread out the field over about a square meter of copper surface to both increase lift capacity and increase system efficiency.

wouldn't that produce very high back EMF unnecessarily complicating the system?

carrotSnack

Wed Oct 22 2014, 09:27AM

Registered Member #4115 Joined: Fri Sept 30 2011, 01:13PM
Location:
Posts: 12

My understanding is that it doesn't use coils but electric motors that spin halbach arrays.
That's what it means when it says it 'focuses' the magnetic field.

Uspring

Wed Oct 22 2014, 11:24AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

My understanding is that it doesn't use coils but electric motors that spin halbach arrays.

Any idea how the array is rotated? Along its long axis?

Rotational axis being horizontal?

A simple magnetic dipole rotated perpendicular to its axis would cause a similar pulsating magnetic field.
I'd expect also some sideway forces from these kind of rotating magnets. By using several arrays rotating at different speeds, these boards could be made self propelled, which seems almost a necessity, since the eddy current braking effects might be significant.

Artlav

Wed Oct 22 2014, 06:15PM

Registered Member #8120 Joined: Thu Nov 15 2012, 06:06PM
Location: Moscow, Russia
Posts: 94

Uspring wrote ...
A simple magnetic dipole rotated perpendicular to its axis would cause a similar pulsating magnetic field.
I'd expect also some sideway forces from these kind of rotating magnets. By using several arrays rotating at different speeds, these boards could be made self propelled, which seems almost a necessity, since the eddy current braking effects might be significant.

That reminds me of a certain device i have, namely an axial flux outrunner motor, that can be used for an experiment.

The magnets on the rotor are flat, and are flipping polarity one after another.

Here is a video of how it behaves next to a slab of copper:

The magnets on the rotor's bottom are spinning in the same plane as the slab, and that produces significant repulsive force.
The motor struggles to spin, the eddy currents try to stop the rotation.
At low RPM it tends to oscillate, but at higher speeds it's floating quite stable.

The motor's body tries to spin out the other way, so i can't let it just float there, but it's hovering on it's own - the strings are only pulled counter to the momentum.
It's quite hard to make it touch the surface, even if dropped - it jumps back up, and maintains about 1cm of distance at full RPM.

There is almost no friction when moving sideways spinning, while there is some when it's not.
All the braking seems to happen to rotation, not to the sideways motion.

I can totally see two or four of these counter-spinning to make a stable hoverboard, but i'm not rich enough to get a sufficiently big slab of copper. :)
Perhaps aluminium...

BigBad

Wed Oct 22 2014, 07:01PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600

Yes, it seems to be a souped up version of this:

Halbach arrays do work, but are a pain in the ass to make. Iron backing plates work almost as well, and more or less self assemble.

If anyone wants to make one, I can help you out with the design parameters; I warn you, you will need some serious neodymiums aka 'death magnets'.

The conductive sheet needs to be roughly half a centimetre or so thick aluminium.

Incidentally, propulsion is easy to arrange; I don't know why they aren't doing that.

n.b. that video's not mine, but I've been working on similar tech, and I've specifically had to work out how to do that

Artlav

Wed Oct 22 2014, 07:13PM

Registered Member #8120 Joined: Thu Nov 15 2012, 06:06PM
Location: Moscow, Russia
Posts: 94

BigBad wrote ...
Yes, it seems to be a souped up version of this:

Drats.
An i was just warming up to print the second motor to do just that...
Foiled again. :)

Seriously, nicely done - it does actually work that way.

Patrick

Wed Oct 22 2014, 07:55PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

All of these methods revolve around a non ferrous conductive sheet below. so sliding through town is out, youd be limited to prepared areas.

The halbach ideas are usable, but i ask, will they spend more on a gaggle of "hover" boards or the skate park. ALuminum and copper are not cheap, and you'd need a certain minimum thickness a presume?

This could all be done, not saying its impossible, and an entry fee to a park eases any such burden. Especially if these whacky young kiddos' take a cult liking of it. Rob Dyrdek should be in on this...

And once im an old grey man im sure they'll have it all figured out.

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