Add Some Edge To Your Blades With Blown-Arc Plasma

If you polled science fiction fans on what piece of technology portrayed by the movies that they most desire, chances are pretty good that the lightsabers from the Star Wars franchise would be near the top of the list. There’s just something about having that much power in the palm of your hand and still needing to be up close and personal to fight with it. Plus being able to melt holes in bulkheads is pretty keen, as are the cool sounds.

Sadly, the day we can shape and contain plasma in a blade-shaped field is probably pretty far off, but that didn’t stop [Alan Pan] from trying the next best thing: a handheld plasma-projecting blade. He starts with a basic Jacob’s ladder. We’ve seen many of these before, but the basic idea is to ionize the air between two parallel, vertical conductors; the hot plasma heats the air causing it to rise until it reaches the top and snuffs itself out, starting the process over again at the bottom. His twist is to force the plasma into a sheet between the electrodes with air from a leaf blower, forming a blown-arc plasma. That’s pretty cool looking by itself, but he also stretched the electrodes along razor-sharp wood planer blades, for extra danger. We have to admit that the thing looks pretty intimidating, even if the plasma doesn’t really pack bulkhead-melting thermal power. Check out the results in the video below.

We’d love to see [Alan] make good on his promise to make the whole thing self-contained with an electric ducted fan or mini jet engine. Even as it is, it’s still pretty neat. It’s not really his first lightsaber rodeo, but at least this one doesn’t need butane.

Thanks for the tip, [baldpower].

8 thoughts on “Add Some Edge To Your Blades With Blown-Arc Plasma

  1. “If you polled science fiction fans on what piece of technology portrayed by the movies that they most desire, chances are pretty good that the lightsabers from the Star Wars franchise would be near the top of the list. There’s just something about having that much power in the palm of your hand and still needing to be up close and personal to fight with it. Plus being able to melt holes in bulkheads is pretty keen, as are the cool sounds.”

    Not sure a confined plasma would do all that anyway, even if we could.

  2. Interesting.

    Furby lasted a lot longer than I expected. I was expecting Furbies CPU (SunPlus SPC81A) to execute a HCF instruction (Halt and Catch Fire) much sooner.

    Some other observations:

    The correct high voltage cable is used for the Cathode (+) side of the LOPT (Flyback transformer) but the Anode side (-) looks like it is only rated at a couple of hundred volts. It might as well be bare wire.

    The Transformer (LOPT) is running totally isolated from the low voltage side (floating). These LOPTS are designed to have a much lower insulation breakdown voltage at the lower end of the coil (where it is less required) than the upper winding that would normally have a much higher voltage when referenced to the driving circuitry. So don’t drive something like this from anything other than a totally isolated battery power source.

    I have seen High voltage (HV) used in heat sink design to break the thermal laminar effect that reduces heat sink efficiency. I wonder if a similar technique could be used instead of the air blower.

  3. I’m wondering if a different orientation might work? I’m not knowledgeable enough to understand the behavior of the plasma in a different configuration… At 4:26, he shows the leafblower with the Jacobs ladder. Would it be possible to make a setup that uses two long, bent sheet electrodes to do the same thing? Effectively, the view of the leafblower ladder at this point would be a cross sectional view perpendicular to the length of the blade.

    In my naive mind, this could result in two parallel blade surfaces with a valley instead of a cutting edge. Air could be blown along the length of the blade. The ladder would be blown outwards, giving the effect of the plasma ‘cutting surface’.

    Please let me know if there are drawbacks I have not considered, so I can adjust my mental model!
    J

    1. Quote: “I’m wondering if a different orientation might work?”
      Electrons are rather light so the orientation is not significantly effected by gravity. Orientation (unless you have another meaning) does not matter.

      Quote: “Would it be possible to make a setup that uses two long, bent sheet electrodes to do the same thing?”
      The shape of the conductor is not greatly relevant as it is a self regulating system. The distance the arc will strike is a result of the voltage.

      Quote: “In my naive mind, this could result in two parallel blade surfaces with a valley instead of a cutting edge.”
      Increasing the surface area of the contact points may slow the progress of the arc. But the arc itself is limited by the joules of energy that create it and any additional surface area does not increase the energy source.

      Your concept is realizable on the provisor if increasing the source and dissipation of energy. However, the increase necessary is probably more substantial than you may expect.

      1. Thanks Röb –
        To clarify my thought about orientation – I believe it could be better expressed as the orientation of the leafblower to the arc produced by the parallel blades. Pushing the plasma perpendicular to, rather than along, the length of the electrodes.

        Your point about the surface area is interesting. I presume the energy required to sustain a wider arc increases with the surface area of the contacts in a nonlinear way.

        Thank you for your insight, it is appreciated!

  4. Would it be possible to use Nitrogen in a backpack cylinder, to operate an overpowered Plasma cutter, to male the plasma blade? Probably be more like a super-torch, but…

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