So, in the land of futuristic feudalism, the board of sword duels has a dilemma. During a duel, one of the duelists added put gyroscopes in his sword. He claimed this was to improve his balance, which was affected by his stubbed toe, but it turned out the gyroscopes where powerful control moment gyroscopes! This gryosword could be swung extremely quickly despite being fairly massive, resulting in extremely powerful impacts. He easily won the duel, seriously maiming his opponent.

The board of sword duels immediately banned these gyroswords after the duel for all future duels. However, duelists started using more covert gyroswords. They would only use the gyroscopic strikes at critical moments, and only increase the power of the strike enough to give them a slight edge. Duelists starting accusing each other of using gyroswords, but this was hard to prove or disprove.

How can the board of sword duels detect these gyroswords, so that they can ban them?


  1. The settings is near future. The first duelist to use a gyrosword was a Noble, who invested a lot of money into it. Afterwords, he started selling them (gyroswords where banned by the board of sword duels, but not illegal). The gyroswords have very advanced control moment gyroscopes.
  2. The gyroswords have the gyros in the blade, hilt, or both.
  3. The gyros are computer controlled. Only gyrosword have electronics in them; legal swords are just one solid piece of material. The electronics are shielded.
  4. Most swords (including all gryoswords) have metal blades and hilts.
  5. To disable the gyrosystem, the duelist allows the gyroscopes to rotate freely, so that the gyrosword will not behave oddly when rotated. When enabled, the gyroscopes are used subtly, so that is difficult to tell that a gyrostrike is being preformed by simply watching the swing.
  6. Custom swords a long tradition in sword dueling, so making duelists use standardized swords is a no-no.
  7. Destructive testing is also a no-no. No duelist, rule-abiding or not, would allow someone to destroy their sword.
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    $\begingroup$ A freewheeling gyroscope still acts as a gyroscope until it stops so without a braking system this won't work. A gyroscope inside a sword blade will be tiny in mass relative to the rest of the sword and have very little effect other than to hamper the movements of the sword wielder. Can you explain why a gyrosword causes powerful impacts? It isn't any more massive than an ordinary sword. It will also be weakened at the place in the blade where the gyro is. $\endgroup$ – chasly - supports Monica Mar 18 '19 at 20:39
  • $\begingroup$ @chaslyfromUK the gyroscopes are used as control moment gyroscopes. By attempting to rotate the gyroscopes (using internal motors), precesion forces rotate the sword. This rotation can be faster than a human can swing the sword. Also, when disabled the gyroscopes still act like gyroscopes, but they don't transfer torque to the sword. $\endgroup$ – PyRulez Mar 18 '19 at 20:43
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    $\begingroup$ Your question is on detecting gyroswords, but what about just forcing competitors to use tournament provided weapons? Like most sporting events the ball and other equipment typically has some standards it has to meet. $\endgroup$ – Culyx Mar 18 '19 at 20:43
  • $\begingroup$ @Culyx see 6. Using custom swords is a tradition of the sport. $\endgroup$ – PyRulez Mar 18 '19 at 20:46
  • $\begingroup$ @PyRulez - Okay, so the fighter just stands there holding the sword loosely and it whizzes around at great speed. So how is it controlled? If there is a controller on the hilt or in the fighter's free hand, it will be easily detected. If an onlooker is controlling it, they will be trying to play a non-pov computer game. $\endgroup$ – chasly - supports Monica Mar 18 '19 at 20:47

Before you can use your sword it gets passed through a powerful electromagnet, which will fry any control system you can fit in a sword, works for any other tomfoolery people try to sneak in as well. A normal sword will not be bothered in the slightest, anything with electronics in it will become a normal sword as any electronics inside are destroyed.

if your sword is legal nothing happens, if your sword contains illegal components it becomes legal through the process. No testing necessary. As long as participants know this will happen and why it is done you should have no problems since consenting would be part of the duel's structure.


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  • $\begingroup$ Wouldn't the shielding protect it? $\endgroup$ – PyRulez Mar 21 '19 at 12:58
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    $\begingroup$ There is no shielding you could put in something as small as a sword handle that could not be easily overcome by a high field strength. Even the best shielding can be oversaturated. $\endgroup$ – John Mar 21 '19 at 13:10
  • $\begingroup$ oh, okay. This is probably the simplest solution then. If they have super advanced shielding, they would also have super advanced electromagnets. $\endgroup$ – PyRulez Mar 21 '19 at 13:11

Shielding only works when you have a ground connection

No ground connection, no shielding. This means your duelists must hide a path to ground. Now, you'd think that just putting the duelists on a rubber mat would solve the problem, but it doesn't, because you can use the negative pole of a battery to act as a ground. So, what are your umpires/judges looking for?

  1. A wire from the hilt passing up the arm.

  2. An electrically conductive glove.

Ah! But your duelists are really sneaky!

They put the battery in the sword! Granted, the battery must be capable of absorbing whatever EM the electronics generate (so your standard button lithium battery won't do), but you could still hide a small battery in, say, the hilt.

  1. Test the weight and balance of the sword (just as the MLB does for baseball bats). Electronics, the gyroscope, and the battery have very different densities compared to to combat-metal. It would be a real challenge to get the weight and balance right.

  2. Finally, plug that sword into a mechanical sword-analysing tester (the M-SAT!). The purpose of this device is to literally swing the sword around in a dozen or two different directions and measure the force required to change direction or obtain a new position. The delta-F of a standard sword would be much higher than the delta-F of a gyroscopically stabilized sword.

Ah-hah! But your duelists are really, really sneaky!

They've adjusted the grip with heat sensors, DNA sensors, all kinds of sensors that will detect when they and only they are holding the sword, thereby disabling the gyroscopes during testing!

  1. First of all, you would still have delta-F variances due to the existence of non-homogeneous material. In other words, a duelist might fool a basic weight-and-balance test, but swing that sucker around and you'd soon know if there was something right there that shouldn't be.

  2. But the problem with heat/DNA/etc. sensors is that they must be active (we're assuming an on/off switch might be easy to find). This means that a mandated DNA sample and some applied warmth would circumvent this solution.

Muahahaha! Your duelists are really, really, really sneaky!

OK, just to get it off the table, one of your duelists invented a psionically-actuated switch, guaranteeing that all the tests can be fooled. A method that simply can't be tested for.

  1. Rule #144/15-3(a): All duelists shall be bound to immolation of themselves and all members of their immediate family should gyroscopic or any other form of assistive technology be found in, on, upon, or associated with, their swords. Testing of swords including but not limited to destructive analysis shall be justified after four (4) matches in which opponents have testified under threat of perjury of the infraction and after review by no fewer than three (3) umpires, who unanimously agree that the analysis is justified. Further, all duelists shall be bound to the dishonor of their extended family such that all members of said family to the fifth generation shall be reduced to the slave class and remain so for six generations or 150 years, whichever is longer (those seeking the absolution of this dishonor must prove their heredity directly to said duelist with certification of DNA tracing held inviolate by government standard 455A07L/4:s, the sample being extracted and stored by qualified personnel pursuant therein). Said duelist shall be held in memoriam in perpetuity, reminding all of their inadequacy as a sapient being. So say we all (praise Glarnak!).
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    $\begingroup$ Good answer. There are two issues however (1) something more dense than combat metal can be put in the sword to make it have the right density and (2) the gyroscope system can be used to simulate the delta-Fs of a legit sword $\endgroup$ – PyRulez Mar 18 '19 at 20:48
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    $\begingroup$ The last point is the most pointed. Praise Glarnak indeed. $\endgroup$ – Joe Bloggs Mar 18 '19 at 21:29
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    $\begingroup$ @PyRulez, (1) But that would be a violation that's easily tested with a surface analysis. It's harder than it seems to hide less-dense material inside something expected to be homogeneous. As I said in my answer, you might fool a weights-and-balance test, but not something more sophisticated. (2) No, actually, it can't. Gyroscopes are meant to change the rules (it's why they exist). You can turn them off, but you can't simulate "normal" because they aren't. Literally, it's not what they do. $\endgroup$ – JBH Mar 19 '19 at 3:01
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    $\begingroup$ The last point will be used by planting gyroswords in your enemy's racks as false evidence. $\endgroup$ – Eth Mar 19 '19 at 10:26
  • $\begingroup$ @Eth, :-) I hadn't thought of that... Well done! $\endgroup$ – JBH Mar 19 '19 at 14:07

If you had used the tag, or its spiritual sister , you could have gyro swords.

Going with , though... Nope.

As for how much force you can get into it... I'm eyeballing here, but I think at best you could fit some PS4/Xbox One controller vibrators into the hilt of a really huge sword such as a dadao (the one in the picture below).

A Dadao

Make the vibrator weights symmetrical rather than asymmetrical and they will be proper gyros. You will get as much force as you would get when a controller vibrates. Those don't keep people from moving them in any direction, nor help in moving the controller in any way either.

Then you have the matter of an energy source. With some simple AA batteries you can feed the gyros of a controller, but for anything stronger you will need some bigger ones. You could use some cell phone batteries and gyros for something more impressive like a sword that stays standing on its tip for a few seconds, but that's the only magic trick you'll be able to pull off with current or near future technology.

You could get an actual cool effect by wrapping the blade in tarnished coil and connecting the coil ends to a set of AA batteries. The sword would then be an electromagnet. It wouldn't be strong enough to affect its movement in battle, it would not attract other blades, but it would be hot to the touch and might just add a first degree burn to a cut. You will lose the magnet the first time you hit anything, though, and might get a few sparks out of the batteries.

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  • $\begingroup$ They are being used as computer controlled control moment gyros, not stabilization gyros. $\endgroup$ – PyRulez Mar 18 '19 at 21:05
  • $\begingroup$ @pyrulez that invalidated one paragraph of my answer, which is my bad and I've removed it. But I think the rest still applies. $\endgroup$ – The Square-Cube Law Mar 18 '19 at 21:08
  • $\begingroup$ momentum energy storage is an active area of research. carbon nanostructures are strong enough to hold a gyro together spinning incredibly fast. in a low-friction environment, they could have long-term energy storage densities limited by the speed of light. if you have one of those already spun up... a potato battery, paperclip and refrigerator magnet could twist it sideways fast enough to propel that sucker at relativistic speeds. I find your lack of optimism in near-future tech... disturbing. $\endgroup$ – BoomChuck Mar 19 '19 at 0:25

As I see it, there are only two possibilities that determine how these swords operate; either they are remotely computer controlled, or there is an internal computer (probably in the hilt) that needs to be activated by some control on the exterior surface.

For the latter, there simply HAS to be a button or some other control access on the sword and that means that a careful visual inspection would reveal it. As for the remote access solution, wifi and mobile signal dampeners, as well as flooding the arena with IR light so standard 'remote controls' are also jammed, would certainly be an effective defence.

All that said, the simplest way I can think of to determine whether a sword is regulation or not is to weigh it.

The process would look like this;

1) Test the volume of the sword by placing it either in water, or a 3d scanner, etc.

2) Take the density value of the metal out of which the sword is forged, work out the weight for a solid piece of metal of that volume

3) Factor in weight of leather and other materials / bindings on the hilt, including jewels, etc.

4) Weigh the sword - if it comes in at less, then there are hollow cavities in the sword that potentially contain electronics.

I'm going to state up front that this is not a perfect system - while the electronics should weigh less, you can always put a gold or lead shielding around the gyro cavities, offsetting some of the weight. Most electronics will also contain at least some gold and other heavy materials and obfuscators will end up packing the gyros and electronics in as densely as possible to minimise the offsets as much as possible, meaning that having small lead cores in your sword could easily offset the weight test.

So, I'd argue all three to help minimise the risk;

1) weight tests
2) visual inspections for controls
3) remote signal jamming as a duelling requirement

This last one also doubles to block any spectators or participants live streaming the event on their phones / go-pros which would be highly distasteful so it's a win/win.

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  • $\begingroup$ I was thinking it would be enabled and disabled with a secret shaking motion, not a button. $\endgroup$ – PyRulez Mar 18 '19 at 21:09

Going low tech with this one.

By their use!

Any judge will be an experienced weapons master. The weight, balance and design of a sword defines the style of 'fight' best suited to it. The fight is detetmined by what is bio-mechanically efficient with that weapon.

There are things you can do with one weapon that simply cannot be done effectively with one of a different design. This is an issue for every training salle. Do you start students with a practice weapon for safety, which can lead to bad form, or take the risk of working with sharp steel from the get-go to give the student a true appreciation of the weapon they are holding and facing! A subject of much passionate debate.

In fencing, not what happens at the Olympics, with weapons of similar style, (anything else is pointless - a backsword user would take a rapier duellist apart - see George Silver) it will always be the skill of the duellist that triumphs, not the quality of the weapon.

Broadly, there are three times in swordplay:

  • time of the hand,

  • time of the foot,

  • time of the hand and foot.

Different attacks, parry's and riposte's are most appropriate to each of these, ie certain things can be done effectively and others cannot.

An experienced judge will quickly identify when a fencer is performing manouvers that are not bio-mechanically possible with an un-augmented weapon.

In addition, because so much of what occurs during engagement is based on muscle memory the user of the augmented weapon will inevitably have a different form, obvious to any skilled judge.

As a side note, having trained in rapier, backsword, hand and a half, cutlass and longsword I cannot imagine any way of incorporating your gyros into a weapon that would not compromise it.

It should be noted that swords are apex designs. Each design suited to a specific purpose, the rapier for instance is not a military weapon. It was developed to permit non-lethal duelling. The backsword however, in the words of George Silver, "... is for the cutting off of arms and legs ...".

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  • $\begingroup$ I can picture sufficiently powerful gyroscopes letting you twist a sword in ways the human arm isn't strong enough to do. I have trouble picturing those gyroscopes being small enough to fit into the hilt of the sword. $\endgroup$ – Mark Mar 22 '19 at 1:36

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