DESCRIPTION
Don’t be dazzled by the new viral hover craze. We were independently working on a near identical system before Hendo went public and you really can do it at home.
Get some powerful magnets, some brushless outrunners, controllers and lipos and a thick sheet of aluminium and you can get things hovering quite quickly. Just make a ring of magnets arranged north south and spin them. It is that easy.
Make them in counter rotating pairs to cancel out the drag and have enough to make a stable hoverbot and you are done. For an aluminium based man carrying version we have done the calcs, it wouldn’t be cheap but is doable with little more technology and
DETAILS
It started at a new years party as we saw in 2014. I drunkenly commited to doing everything in my power as an engineer to make a hoverboard work by ‘the date’ 21/10/15. I get the impression I am not the only one…
I roped my Maker Faire buddy Mark, the other half of Jelly and Marshmallows (www.jellyandmarshmallows.co.uk) to assist, and we started work.
We researched various technologies for levitation, from aerodynamic to ultrasonic, but always the most convincing was magnetics. A while back (2008!) I had bought a strong magnet with the sole purpose of investigating whether permanent magnets could be used to generate eddy current levitation similar to Laithwait’s 70s magnetic river demonstrations
It turned out they could, and that as far as I knew the principle hadn’t been explored much.
Our next step was to make an array of 8 magnets in a 3D printed rotor that could be spun by a drill. The magnets are 20mm N35 neodymium magnets, alternating north south as you go around the circle. We bench tested this over a set of scales with some 3/4″ aluminium on.
This achieved 2kg of lift at 1cm and 1kg at 1 inch separation. Not bad for a first try.
The power loss is created by drag from magnetic breaking, and the 3kg aluminium plate was on the verge of spinning, highlighting that long term this would need to be done in counter rotating pairs. Miniture test below lowered the torque to a level our meter would measure. This test had lift, torque, RPM, motor voltage and current all recorded… science folks!
A
few variations to explore array arrangement and trying laser cut and routed plywood, along with more accurate lift efficiency tests and we were soon ready to make a chassis with a pair of rotors. Pardon the untidy tape holding the cables in.
Testing showed we could easily achieve lift of up to 2cm but it was like trying to balance a stationary bike that is twitching sideways. Impossible. Still by holding the cable ties it could be kept from rolling or sliding away and you can see the hovering:
From there we realised it was best to go quad rotor so we quickly put together a quad rotor chassis in time to demo it at Maker Faire Brighton, UK. As yet I don’t have a decent video of it but this was a walk around of our stand at Maker Faire
When it is sliding around and not making a horrible clattery noise it is hovering. The lowest part is the rotors because we broke the surround we made, so whenever it gets too low as it moves the spinning magnets clatter against the aluminium. The motion is Mark attempting to steer it (you can see he is holding a wii nunchuck). The control is VERY difficult at present and still very much in development so it needs help quite regularly to stay on the alu sheet.
I will post more videos when I get the chance to take them!
PROJECT LOGS
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New, better video
jellmeister • 10/31/2014 at 19:37 • 0 comments
So I finally managed to get a better video recorded…
The original set up used a Wii Nunchuck arduino to radio control the 4 motors, mixing channels as required to control the hoverbot. Today we didn’t have all that running so we just had an RC transmitter making the already difficult control even harder. The design is unstable and our intention is to add a 6DOF gyro/accelerometer stabiliser circuit, but for now it spins off rapidly. The last part of the movie we tethered it to stop it spinning off and it hovers stabley:
As you can see in the tethered part of the video, the left blue rotor isn’t floating as high. Its motor is slower for some reason (supposed to be the same but cheap motors…). We are running the black rotors at part throttle to compensate so could go higher if they all worked properly. Also we only filled half the rotor magnet holes, so we need to fit more and see how much better it is.
Next step is definitely gyro stability though:)
