Sword harmonics

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EZKleave

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Sep 14, 2004
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From reading about modern swords like the Angus Trim blades and others that have done serious work on the physics involved in sword use I've come up with an idea for an extremely non-traditional sword. Its a high tech blade that would probably not be able to use the traditional materials swords use, but I think in theory it could make them far deadlier weapons. Swords vibrate when they hit things, like everything else, and if you hit with the right part of the blade these vibrations will not adversely effect your cut. There are several technologies being used in the real world for other purposes like "active noise cancellation" in some cars to muffle engine sounds and IIRC some high performance downhill skis use a similar system to maintain contact with the ground. It involves a small "microphone" that detects vibrations, a small chip that calculates the "opposite" noise" and a speaker (usualy the "microphone" serving a dual role) that plays the sound to cancel the original wave. In skis this curcuit is just a film of piezoelectric materials and a few tiny "chips" that calculate the variables, it is self powered by the vibrations and does not require an outside power source. In theory a sword could contain such a film along its length that it could use to cancell vibration along the sword, no matter where along the edge the vibration started. Again, in theory this could potentialy turn the blade's entire length into a "sweet spot" or perhaps into some sort of passive "vibroblade" to borrow a science fiction term. I'm just wondering if anyone has heard of anything like this being tried with blades?
 
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No, and it wouldn't be practical.

Acoustic vibration--the type you're discussing when you mention wave cancellation, etc.--is a sympathetic response. For example, the noise of the air rushing around the frame of a car provides a fairly steady waveform. After a second or two of sampling, a digital signal processor produces an "average" waveform for the noise, inverts it, and plays it back. About 90+% of the sound is subtracted from the air.

Harmonics is a separate issue from this--basically, a series of different vibrations can produce harmonic vibrations at different intervals, and this tends to be particularly stressful against components. Skis, for example, can produce harmonic vibrations that cause them to wiggle and shimmy; a harmonic cancellation can limit this to some degree. Electronic equipment dealing with multiple voltage phases benefits from this, as well.

Striking a sword against something produces a highly variable and rapidly attenuating shock vibration. By the time the DSP could sample the waveform, it would already deplete... and if it inverts the initial shock and played it back--you'd have a near-equally powerful vibration...just backward.

You're dealing with energy on a shock vibration, not acoustics. The best you can do with shock is to absorb it by some dampening means--and that would severely hamper the weapon's performance against real, soft targets.

I suspect--and anyone else should feel free to reject or confirm--that a sword's sweet spot should already be along its entire blade edge.

Now, if there were some way to electronically control the temper of the steel by applying microvoltage, then you might be able to "blunt" a blade on a block but reapply an edge on a strike...
 
My background is in engineering, and I see several problems with your idea.

1) You want to take a simple device (steel plus handle) and make it complicated. This is never desirable. Vibrations can be dealt with in other ways, and it is not a serious enough problem to warrant the extent to which your changes will complicate the sword.

2) Noise cancellation is a very localized effect, and vibration cancellation is no different. In your example, it would need to be localized to the point of impact, or you would induce an even worse vibration. This is never simple or 100% effective, and given the irregular geometry and numerous angles that a sword may take impact, the calculations are going to be complicated exponentially.

3) Simple energy laws dictate that using piezos to power an IC and more piezos aren't going to be very efficient. Your 'cancellation' is going to be more like 'dampening.' Dampening can be done in much simpler ways.

4) Piezos are not bulletproof, and a film along the blade is going to be sharpened away or broken. A friend of mine has a snowboard that used piezos to make lights flash on the top of the board when he took jumps. They worked one day, and then he got hit by a skier.

If you are interested in reducing vibrations, I would seriously recommend looking more into material sciences and blade geometries.
$0.02
 
Active vibration dissipation and cancellation... does the technology have anything signifigant to offer high impact cutting blades?
The basic technology exists, and while I'm not completely familiar with it the basic premise is that a sound can be cancelled out or dramaticaly muffled by playing the opposite sound. Many luxury cars use this approach to reduce engine noise reaching the passenger area. A while ago I saw a discovery channel clip about experimental skis that used a similar technology to help keep the ski's in full contact with the slope and to reduce vibrations reaching the skier.
When a sword hits something, it vibrates. At the right spots the vibrations do not occur, these are basicaly sonic fulcrums (there probably is a technical term, but they don't cover that stuff in the GED) and in a well made sword they occur at the "sweet spot" and the hilt. You hold one of these spots and try to hit the target with the other one.
We've "tuned" these blades variously since before we understood the physics behind the phenomenon. Until recently this was all we could really do, build the sword so that the vibrations will only affect parts of the sword that can withstand them without affecting normal use. The hilt is over one sweet spot because too much vibration will eventualy loosen it. The sweet spot on the blade is used to cut because it will not dissipate the energy put into the cut as much as the rest of the blade would.
Until recently we could only controll this passively, by designing the sword to make these "sonic fulcrums" or "sweet spots" fall where we wanted them. Today there is technology that could actively counter these vibrations... we could make the entire cutting edge of a blade "harmonicaly balanced".
And for the record, I'm not actively pursuing this... its just a thought that popped into my head.
 
As has been stated before, vibration dampening in skis, acoustic dampening in headsets and car cabins, and the shock vibrations generated by a blade hitting an object are all very different beasts. In active noise cancellation, a very localized effect is created by "listening" to incoming sound waves, and generating new sound waves that neutralize the incoming sound. These systems can only decrease ambient noise, and they work best in environments with relatively regular, low-level background noise. Intelligent vibration dampening skis work by converting the energy of vibration into electrical energy, and use that energy to change the material characteristics of ceramic panels embedded into the skis. This can't work in a sword - there are no real options for electrosensitive materials that can withstand the force generated by a sword blow. If you embedded electrosensitive ceramic panels into a sword, you'd have a whole slew of problems - not least the issue of structural weakening because of all the cavities you'd need to insert the ceramic panels. Also, the shock vibrations generated within a sword are not regular the way engine noise and ski vibrations are. The energies involved are also much greater - I don't think any piezoelectric dampening system would generate enough power to significantly dampen the shock of a fudged sword strike.

As far as I know, there is no system, at least not on the market in some form, that can actively dampen the high-energy, discontinuous shock vibrations generated in something like a sword. So the technology doesn't really exist to do what you're thinking - at least, not if you want the sword to remain a functional sword.
 
Yeah, I doubt the materials used in the skis would be enough. Nitinol might work, or carbon nanotubes, maybe even electroactive polymers. There is a new fabric I heard about that uses nitinol fibers interwoven with the cloth that electrifies itself to temporarily make itself rigid in order to resist punctures and slashes. I don't remember the specifics, I'll try to find the site I found it on...
This sword probably would not be made of steel, it would probably need to be made as a composite.
The specific method of active vibration cancellation isn't really what concerns me as much as whether the basic concept would work... and if it would help in this application.
As for passive methods to deal with (or harness) these vibrations... what is out there aside from careful balancing to place the "sweet spots"?
 
As has been mentioned, swords are fairly simple tools (handle and blade). Folks for many generations used them with out the aid of high tech gadgets. Perhaps the ability/skill to strike properly with a sword is all that's really needed. :rolleyes:
 
Perhaps I should have more clearly stated that this is just a theory... and one that I fully realize has little to no practical benefit in our modern world, no niche to exploit. A sword is an extremely complex piece of metal... it is elegant but not simple and references to the simplicity of sword construction fail to give credit to the meticulous work required to make a good sword.
This is just an attempt to come up with something that advances the science of swordmaking... wich has IMO regressed rather severely in all aspects aside from materials, and excepting some deicated individuals who make them as pieces of martial art. Modern swords are not typicaly revolutionary, it could be said the designs have been honed over the millenia and have already reached their peak but I refuse to believe we have nothing left to improve upon. One of my ideas for how to take sword technology further is active vibration management... I'm curious as to anyone else's ideas about either how to make it work or alternative methods to improve swords given our modern scientific knowledge.
 
There are practical considerations for swords that rule out almost all reasonable candidates for polymer or composite construction. The first is weight - a really light sword isn't really a sword. The inertia of the sword is what drives it through cuts. Also, remember that when it comes to composites and polymers, "rigid," "hard," and "strong" are relative terms. No other metal comes close to the performance of steel in swords. Similarly, no composite material can come close to the material properties that a sword needs. Laminate materials would have to deal with massive shock forces trying to rip apart the discrete layers. They wouldn't hold an edge. They would crack or bend at forces far lower than what steel can tolerate.

Nitinol is a facinating shape-memory alloy. But it is not suitable for sword blades. It simply doesn't have the material properties necessary. Nitinol-based composite materials? You'd still come up against the fundamental limitations of composite materials. You might as well use a pool noodle.

The point here is that the basic concept is flawed - any reactive system for dampening sword shocks has to 1) recognize the fact that a shockwave has been generated, 2) create a new waveform with the characteristics and enough energy to dampen the original shock and 3) do all this fast enough to prevent the shock from reaching the user. Existing noise cancellation technology and piezoelectric dampening systems are not applicable here. There are no systems I can think of that would be able to generate enough force to negate the initial shock wave and still fit into something resembling a sword blade.

As for existing passive methods - the best have turned out to be the most traditional. A well-made blade with "sweet spots" suited for the swordplay style of the wielder, and a handle designed to reduce felt vibrations. Softwood handles wrapped with cord, things like that. Sometimes old ways endure because they really are the best. Titanium blades, composite handles - a whole slew of advancements have been proposed for swords. All were eventually abandoned, because they didn't function properly as swords.

*Also, consider this - part of the reason why you feel a relatively large amount of shock when you strike something with a sword is because the sword itself is capable of tolerating the large stresses involved in receiving such a shock. A composite blade would likely fail in the face of a similar strike, which kind of makes vibration dampening a composite blade a moot point.
 
EZKleave said:
Perhaps I should have more clearly stated that this is just a theory... and one that I fully realize has little to no practical benefit in our modern world, no niche to exploit. A sword is an extremely complex piece of metal... it is elegant but not simple and references to the simplicity of sword construction fail to give credit to the meticulous work required to make a good sword.
This is just an attempt to come up with something that advances the science of swordmaking... wich has IMO regressed rather severely in all aspects aside from materials, and excepting some deicated individuals who make them as pieces of martial art. Modern swords are not typicaly revolutionary, it could be said the designs have been honed over the millenia and have already reached their peak but I refuse to believe we have nothing left to improve upon. One of my ideas for how to take sword technology further is active vibration management... I'm curious as to anyone else's ideas about either how to make it work or alternative methods to improve swords given our modern scientific knowledge.
Click to expand...

Perhaps modern materials are making a difference in the reproduction market. Mill produced steels such as 5160 and 1075 are probably much better in quality and consitancy than period steel. Modern heat treats used by Angus Trim, Albion and Arms & Armor are again probably far superior than period pieces received. I'm not sure that much more could be obtained using more "advanced materials" - what's the cost benefit analysis? Would a blade with "active vibration management" really outperform a normal steel blade in hand?
 
In terms of real world performance you would very likely notice no real improvement with a composite "active vibration management" sword... it would probably work LESS well in fact. I was wondering about this from a purely intellectual perspective, not in terms of a marketable product. Under controlled conditions, would this approach result in superior performance in a single, limited aspect of sword function? I fully realize the supremacy of steel for sword construction and I'm not suggesting in any way that it is obsolete or would be made so by sucessful development of this concept.
This would not be a sword to chop up watermelons with, or take out to an SCA meeting to beat on the black knight... this is just an idea to apply some new ideas to an old technology, not to make the sword a better weapon but to come to a better understanding of how swords work on a deeper level.
 
A composite sword would not be at all in the same league as a real sword - it would be more like a practice weapon. For all the reasons I stated above, a composite sword simply wouldn't function as a sword - given, of course, that we hold this composite "sword" to the same standards as a traditional sword.

However, if you're looking at a single aspect of sword function, you're not really thinking about swords at all. A sword is the synthesis of all its properties, and isolating any single force that a sword experiences in typical (i.e., battle) usage is basically a question of simple physics, rather than anything specific to swords. So the question becomes "can large shocks propagating through certain materials be dampened through an active mechanism?" A better application of this question would be to things like hammer and ax shafts - fields where composites are truly worth consideration, and are actually in use.

The stresses placed on a sword are very well understood - this was true even in medieval times. After all, smiths then had the best possible teachers - blades broken, warped or otherwise destroyed in actual combat. Curved swords, falchion-type blades, tip designs, single vs. double edged swords - all these are evidence of the vast store of knowledge available to smiths who did their work when swords were still a battlefield weapon. Even now, the best swords made in modern times simply use cleaner, better formulated steels to address problems that were well-known a thousand years ago.
 
I'm not actualy disagreeing with what your saying, the old time swordmakers and fighters did have a very high level of knowledge of the forces acting on their weapons. They found elegant solutions to deal with these forces, solutions that work even better when combined with modern materials. I don't want to imply that these solutions no longer apply, or even that there is a "better" way to do things. Think of it this way, the X-planes never flew in combat but they provided information to make future warplanes more effective. Some X-planes were complete failures, some changed the fundamental approach to the science of flight. This is far from a pefect analogy... but I hope it illustrates the point that I'm not trying to say that my idea would make a "better" sword... simply that it might help provide information about swords and their function. I believe that because swords are no longer considered effective weapons, the technology behind them has been left to stagnate and no advances have been made since swords became stainless steel dress uniform pieces. A few people have kept the technology from regressing TOO badly, serving more in the role of curator than innovator. The sword market is far to small to encourage much innovation, with most sword enthusiasts apparently locked into a "good old days" mentality where loyalty to old forms and styles is the among the greatest concerns. This isn't a bad thing, but I find it sad in a way.
Active vibration controll is a grossly inefficient way to merely dissipate extra energy in a sword strike... as has been said there are already a multitude of elegant passive approaches to deal with this problem that have been proven both in the blacksmith shop and the field of battle. However, active vibration controll has the potential to increase the effectiveness of a sword strike, with our technology today very likely within controlled conditions only. It could allow extra energy to be directed to the blade as needed without producing extra strain on the swordsman (think "vibroblade" from various science fiction sources). I would like to stress that this is only potential, and to achieve such an effect would require an effort far beyond my abilities. By my understanding this is technically possible, but extremely difficult and would likely not provide immediately tangible benefits to the sword making industry. If I am wrong in my underlying idea (and I might be, I have a lot of half baked ideas :)) then so be it, but if the difficulty of turning this theory into reality is the only argument against pursuing it then I believe my original hypothesis has in fact survived unscathed.
 
I don't think my first post sank in. This is NOT feasible with any current or prototype technologies available. If they created piezos that could be smelted into the steel and resist the repeated impact that a sword goes through, maybe this would work with intensive calculation of the different frequencies each section of the blade produces, and a damn good engineer to program an IC that can perform extremely complicated calculations on a variable power supply with negligible power up time. It could happen, and I don't want to crap on technology (since it keeps me employed), but I think you already figured out why it's not being pursued. Swords have their niche, but are otherwise dated.

Something else to keep in mind is that the various swordplay styles would not likely benefit from this technology. Those that employ hacking strikes aren't going to use the entire length of the blade, they are going to utilize the outermost arc, which is the most devistating for that type of attack. Styles that employ slicing attacks don't induce a lot of vibrations on the sword to begin with. Those that use thrusts will inherently produce minimal vibrations.
 
Like S2nd said, the original hypothesis is NOT supported by existing technologies. A sword cannot be treated as a point source, the way the ear can be isolated. Nor can it be monitored by multiple sensors from the outside, the way a car engine can. Composites are not functional as blade materials, so that's out. And even if piezos could be smelted and forged into a steel blade, there would still be the issue of power output - how would you generate enough force to neutralize the shock of a sword strike?

The idea of a "vibroblade" is not actually a sword that dampens vibrations. It's more like a souped up electric carving knife. In such a blade, vibrations are induced in the blade to increase cutting power. With a sword, which should already be capable of lopping off limbs without such enhancement, such a feature is useless. Also, think of the mass involved - an electric carving blade can achieve high oscillation rates in a small package because the blade's mass is minimal - maybe an ounce or two. Compare that to 2-3 pounds for a functional sword. You'd need a full fledged motor to do something like that, and you probably still couldn't get a proper oscillation going because of the inertia of the blade. It would probably wobble, rather than vibrate. And, of course, the user would experience a constant uncomfortable vibration through the handle.
 
This has been an interesting discussion, but in the end aren't you trying to reinvent the wheel? I am not saying that everything that can be discovered about swords has already been done- our understanding of exsisting sword forms is incomplete. Perhaps we should fully understand the sword as it currently exsists before moving on?

Seven or eight years ago 'harmonics' was a new idea to at least 99% of sword enthusiasts. Now we have siimple and complex harmonics, Polar Moment and many other aspects of sword design entering the discussion. What will we know in eight more years? I think that we should 'catch up' to the exsisting technology before we seriously contemplate trying to exceed it. Just my opinion.
 
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