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Post by perignum on Mar 24, 2021 12:36:58 GMT
Hi guys and gals,
I was trying to grapple with the thorny issue of describing sword flex. It seems that there's no real objective way to describe it. I'd like to propose the method that Blackfencer use. They give a flexibility quotient in kilos.
The method is basically to put a block of wood or something on a weighing scales, set it to zero and then place the sword point down on it. Then press until the sword flexes 2cm out of true and record the amount of kilos in pressure exerted.
Using this method I got 9kg in flex for my Windlass Erbach, 15kg in flex for my Windlass German Bastard sword and 12kg in flex for my Deepeeka Tewkesbury Longsword (incidentally, a very good sword!)
I think this might provide some sort of standard to measure sword flex. We can even express it as a decimal: Erbach stiffness is 0.9, Tewkesbury 1.2 and GBS 1.5.
To put it in context, the Erbach is flexible and capable of cutting and thrusting through leather-wrapped plastic bottles. Any more flex, though and I think it would be unsuitable for thrusting. Therefore a stiffness score below, say, 0.8 would be be very flexible. On the other hand my GBS is very, very stiff, anything over a stiffness of 1.5 is particularly rigid.
At the risk of sounding like a 1980s British comedian, would anyone like to compare stiffness?
Edit: By the way if the MODS consider this should be in a different forum other than 'Reviews' please feel free to move it.
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Post by Adventurer'sBlade on Mar 24, 2021 14:28:35 GMT
Won't the degree of flex off center to achieve 2 cm displacement change with blade length?
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Post by perignum on Mar 24, 2021 14:30:51 GMT
Won't the degree of flex off center to achieve 2 cm displacement change with blade length? It will but that can be taken into account when describing the sword. It's better than nothing except vague terms like 'whippy' imo. Basically, if we get a big enough data set we can compare swords of similar stats to each other beyond just weight, length, balance etc. We might be able to give some sort of comparative framework so we can describe 'flexibility'.
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Post by RufusScorpius on Mar 24, 2021 14:53:27 GMT
Won't the degree of flex off center to achieve 2 cm displacement change with blade length? It will, but with enough data collection a compensation factor for length can be applied on a chart. I like the idea, even if it isn't perfect, but it at least gives some empirical data from which a comparison can be made.
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Post by perignum on Mar 24, 2021 14:59:06 GMT
Cheers, Rufus. A friend of mine has some sort of a cut and thrust sword. I'll see if he can measure its stiffness and I'll help him identify it. I've a feeling it's a Deepeeka broad-bladed 'rapier'.
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Post by Adventurer'sBlade on Mar 24, 2021 15:00:09 GMT
I'm all in favor of a standardized method of testing that is easy to perform at home and shouldn't damage a blade. Maybe someone smart can come up with a formula that accounts for length as a variable against the force to bend 2 cm to get a flexibility score.
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Post by Adventurer'sBlade on Mar 24, 2021 15:02:58 GMT
Or change the deflection distance based on blade length. E.g. flex it one millimeter off true per inch of blade length and use that force reading.
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Post by perignum on Mar 24, 2021 15:18:12 GMT
I think people need to keep in mind that this should be easy enough to do and gives a sense of how flexible the blade is as a blade. I don't think we need to get tied up in knots about determining the molecular properties or comparing EN45 to other steel types. We're looking at swords of comparable length and weight and adding in a basic flex test.
I'd love if someone had a really whippy longsword that they could measure and compare against one with similar blade profile that is considered more rigid.
Like if anyone out there had the Windlass renaissance longsword that was considered just a tad too flexible. You know, the one with the side rings and half-wire grip.
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Post by perignum on Mar 24, 2021 15:40:33 GMT
Or change the deflection distance based on blade length. E.g. flex it one millimeter off true per inch of blade length and use that force reading. I like this. Another way, if we have enough data and we're dealing with Medieval/Renaissance stuff, is for people to use Oakeshott's Typology. For instance the Windlass Erbach is listed as an Xviiia. There are a lot of reproduction xviiia's out there. Let's see how they compare.
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Post by RufusScorpius on Mar 24, 2021 16:26:48 GMT
I agree that this idea should be "quick and dirty" and not get wrapped up in the weeds about steel formulations and such. I see it as a home-based test method that can give a general overview of a sword's flexibility, and by extension, a little insight into the heat treating. I don't see any value in breaking it down into specific sword types when the idea is to simply put a number to the term "flexible". If a sword is 1.5 on a flex scale, and it's a rapier, and another is also 1.5 but it's a gladius, then so be it. The test will give you a number you can use to determine if 1.5 is what you want in the blade or not.
Any detailed evaluations should be done at the manufacturer's level where specific data can be applied to the testing model.
I, for one, would love to see a "flex number" in advertising.
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Post by perignum on Mar 24, 2021 16:43:51 GMT
I agree that this idea should be "quick and dirty" and not get wrapped up in the weeds about steel formulations and such. I see it as a home-based test method that can give a general overview of a sword's flexibility, and by extension, a little insight into the heat treating. I don't see any value in breaking it down into specific sword types when the idea is to simply put a number to the term "flexible". If a sword is 1.5 on a flex scale, and it's a rapier, and another is also 1.5 but it's a gladius, then so be it. The test will give you a number you can use to determine if 1.5 is what you want in the blade or not. Any detailed evaluations should be done at the manufacturer's level where specific data can be applied to the testing model. I, for one, would love to see a "flex number" in advertising. That's fine by me, pal. If anyone has any swords and a weighing scales handy, throw up a few stats in this thread and we'll try and build a bit of a data set.
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Post by RufusScorpius on Mar 24, 2021 17:20:09 GMT
All you need is a vice or clamp, a fish weighing scale, a yardstick and a ruler. Clamp the sword in the vice 3" from the tip, set up the ruler in a T across the yardstick at the hand guard level, then pull the sword with the fish scale and read the number at 2" or 4cm of flex (whatever we determine the standard)
Then all you need to do is look at the chart length/pull weight and see the flex number.
Sounds like a fun experiment.
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Post by perignum on Mar 24, 2021 17:44:57 GMT
All you need is a vice or clamp, a fish weighing scale, a yardstick and a ruler. Clamp the sword in the vice 3" from the tip, set up the ruler in a T across the yardstick at the hand guard level, then pull the sword with the fish scale and read the number at 2" or 4cm of flex (whatever we determine the standard) Then all you need to do is look at the chart length/pull weight and see the flex number. Sounds like a fun experiment. It does, indeed. I'd be curious to see the difference in flex number between two swords of the same general style. The Munich cut and thrust from AA vs the Windlass version. The Cold Steel Competition Cutter's flex vs the Windlass Arbedo. Albion Principe vs Ronin Katana Euro 3 or Darksword Armoury Alexandria. I'd also be very interested to see the difference in flex number between the various replica rapiers out there. I know there's almost universal consensus that most replica rapiers are too flexible. They'd be good fun to compare and see. Also it'd be really interesting to see the flex number of a sword that people considered 'too whippy', just so we can put a number on it for comparison.
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Post by Deleted on Mar 24, 2021 20:08:32 GMT
To me, the method described has been implemented in the past. That includes proofing military swords in the 19th century. The other, more common, proof test was simply bending over a form. What neither address clearly is where on a blade is being deflected in an ordinary thrust. For instance, Nick Thomas sat down with a large sample of spadroons last month and generated a passel of weight to deflection information and I suppose someone could classify the weight to deflection categories but that still misses where on a blade the deflection is happening. To me, a score modulus is not only somewhat ridiculous but useless. Some are going to love such. Vincent LeChevalier, Peter Johnsson and others dwell on numbers a great deal and Vincent might enjoy doing up some equations for such a project but to me, the location of deflection will mostly be lost. See Paradoxes of Sword Design, blog.subcaelo.net/ensis/documenting-dynamics-of-swords/ and a host of other articles are by and large far beyond a lot of casual sword collectors and a first impression reviewers ability. More bang on a pommel to determine a cop and waggle from the grip , rather than do the research to mathematically plot pivot points and moment of inertia. Pressing on the point does show where a blade deflects but so far, few are plotting the math of the deflection itself. I judge the flex in a different way and let the weight of the sword determine where a blade has its point of deflection. Using a thumb or index finger, it shows me in a manner close enough and the weight of the sword easily enough determined. One could use a different fulcrum jig but even if I need a gloved fist on a big sword, the deflection a is apparent enough to me and the sword weight a given. Absolutely though, please no strongman sword bending overhead. Carry on GC
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Post by Deleted on Mar 24, 2021 20:23:30 GMT
What I am getting at that is if a blade has flex in the foible and not the mezzo or forte, the blade can still be quite a thruster. If the flex is in the mezzo and forte, you have limp noodles.
Whatever
Lay on, Macduff
GC
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Post by RufusScorpius on Mar 24, 2021 20:37:02 GMT
I think you missed the point. The test is for us lowly users to do at home so when we talk about "flexibility" we will have some kind of standard by which to conceptualize what we are talking about. Blade performance in the dynamic is outside of the scope of this project.
It's a home test for us schlubs, not a scientific analysis.
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Post by Deleted on Mar 24, 2021 20:49:49 GMT
I think you missed the point. The test is for us lowly users to do at home so when we talk about "flexibility" we will have some kind of standard by which to conceptualize what we are talking about. Blade performance in the dynamic is outside of the scope of this project. It's a home test for us schlubs, not a scientific analysis. My view is exactly that and the most basic without any math required. A scale for the sword's weight and that's it. Even without the weight and any numbers, holding it horizontally by the point and letting the sword's mass sag the blade shows where the blade is flexible. Likewise your vertical vise routine and even pushing against the point on a scale but both of those ignore that a flexible blade may still thrust well. You are seeking some magic number and scoring system when common sense might better suit some. Cheers GC
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Post by RufusScorpius on Mar 24, 2021 20:53:07 GMT
I have no faith in common sense, that is why I advocate for a measurable parameter. A factual number, even if it's relevance is debatable, is still a data point. Collect enough data points and you can then create something resembling truth.
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Post by Deleted on Mar 24, 2021 21:36:43 GMT
I have no faith in common sense, that is why I advocate for a measurable parameter. A factual number, even if it's relevance is debatable, is still a data point. Collect enough data points and you can then create something resembling truth. Uh huh "It's a home test for us schlubs, not a scientific analysis." Okee Dokee
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Post by perignum on Mar 24, 2021 21:52:05 GMT
I have no faith in common sense, that is why I advocate for a measurable parameter. A factual number, even if it's relevance is debatable, is still a data point. Collect enough data points and you can then create something resembling truth. Uh huh "It's a home test for us schlubs, not a scientific analysis." Okee Dokee I'd envisaged it as a comparative tool. I've read so many posters belly-aching that they bought a sword, it looked great but it was 'too whippy' or a description of a blade as 'flexible without being whippy'. I just felt that it's very easy for the community of 'schlubs', to which most of us belong, to compile a comparative store of information all based off a standard measurement by which people might be better able to gauge a sword's flex and not get blindsided by unwanted whippyness. For instance, I wouldn't want a sword any more flexible than my Erbach but I have no idea of even roughly how flexible a sword is until I buy it. Even distal taper is sometimes impossible to find info on or doesn't communicate the rigidity adequately. I think it'd be a good idea for people to have a simple, ballpark, method of conveying blade flex to other hobbyists that we can all easily access. That's why I'd be interested in establishing a base line consensus for 'too whippy'. On this nascent scale we're working on I imagine it'd be around 0.7 but without people's own data we're left with vague assertions of 'well, it's flexible and some people might find it too whippy'. The question that I hope to answer is, 'Too whippy compared to what?'
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