Jamie MacIver: HEMA Instructor

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Resources This page collects various resources we’ve produced and made available to the HEMA community. Most of these resources are being provided open-access and free at point of use so that they bene…

Several people have contacted me about my last post - thanks for the feedback, it is appreciated (especially when you disagree with me). I've had about five separate conversations on the practice of removing the sword mass before measuring the flex, and I decided to put things to the test rather than speculate.

Here are the hypotheses implied by needing to zero off the sword mass:

First Hypothesis: If two swords have identical blade flexibility and different masses they will result in a raw reading on the scale that that varies by the difference in mass of the swords

Second hypothesis: if the force of gravity is changing the reading by the sword mass then we will have different readings when performing the flex test horizontally and vertically (because gravity is only in effect vertically)

I put both to the test using my cup-hilt rapier, which let me take off half the mass while keeping the blade by just removing the cup/handle/crossguard unit. Because of this I could only test pommel flex (no crossguard to push on in one condition), and I tested both with and without cup in a horizontal and vertical position.

The vertical test with and without the 500g of hilt resulted in exactly the same reading. The horizontal test actually resulted in slightly *higher* values, not lower - if the full mass of the sword and the effect of gravity was relevant we'd expect much lower readings (about 1kg lower with cup and .5kg without).

Now to be clear: I don't think I've broken gravity, I think the higher readings are because I had a much harder time getting a consistent bend horizontally than vertically. But this quick test with a single sword shows that both of the above ideas don't stand up to contact with the real world - if the mass of the sword is affecting the reading at all it certainly isn't 100% of the sword mass that is relevant.

This is because fundamentally we are measuring the force on the scales, not the force *we* are applying, nor the total force applied by any source. Most of the force acting on the sword is going into bending the blade, and so not going into the target - all we care about is how much is going into the target.

If you have your own swords that come apart and want to do your own tests, I would welcome more data points - send them through.

I've been asked three times in the last month why a Regenyei Medium Blade listed as 11.5kg-13kg might not pass the Wessex League / Albion Cup new flexibility standard at 16kg. The short answer: there is no standard process for measuring blade flexibility and small differences in methods can lead to wildly different results. I've been meaning to write an article about this for a while but not quite gotten around to it - so you'll have to settle for a long facebook post instead.

Many UK tournaments have started getting more rigorous about testing swords. As far as I'm aware all of the UK events currently measuring flex use a version of the "Sword Buckle Test" written about by Sean Franklin in this article: https://swordstem.com/2022/10/17/sword-flex/ (at least this Wessex League, Albion Cup, London HEMA Open and Herne's Cup)

The basic test involves pushing a sword point first into a scale. The value on the scale when the sword reaches a certain level of flex is the result. There are three variations that can lead to changes.

UK events do this measure by holding the crossguard and either pushing or pulling into a scales. This is recommended in the article and many manufacturers use this same method.

Some people do the same thing but push from the pommel - this will give you about a 20% lower reading compared to pushing from the crossguard, although it varies. If you multiple a pommel reading by 1.25 you will get roughly the crossguard reading, or 0.8 in reverse.

The amount of bend you put into the blade also matters, but less. At Wessex we recommend pushing the blade down about 10cm to get a good bend: there is a small, linear increase of force measured by increasing the bend but it is tiny (about 1% per extra cm) and so a precise distance is usually not that important - anything from 5-15cm will be within the margin of error for the test. 10cm is about right because almost no sword will permanently deform at that level of flex and we wouldn't want to break a sword during kit check.

It's not clear if pushing from the pommel or crossguard is better or worse. Pushing from the pommel seems to be easier to get wrong by introducing lateral force and might vary more from the crossguard with longer handles, but neither have really been tested against actual force transferred with the sword and which is a better approximation of "how likely the sword is to ouch someone" isn't known.

But for reasons I cannot understand some manfacturers also subtract the weight of the sword before applying force. This is not just different: it is wrong and has no purpose. It means the reading will be out by exactly one sword weight. We are measuring the force required to bend the blade, where that force comes from is irrelevant. This can be proven to be wrong by measuring vertically and horizontally: you get the same reading for blade flex but only vertically includes the mass of the sword.

Now if you've made it here you probably want to know about Regenyei Mediums. These swords are unfortunate for two reasons. First, Regenyei both pushes from the pommel and subtracts the weight before pushing - although they also push to around 10cm bend. Second, they happen to hover around the maximum allowed flex at the Wessex League and Albion Cup at 16kg.

https://regenyei.com/about/flexibility/

The listed flex for Regenyei Mediums is 11.5-13kg, and the mass is around 1400g. With some quick maths (add the sword mass then multiply by 1.25) this gets us a flex of around 16-18kg. In reality there is some margin of error, but this means that the more flexible mediums will pass and unfortunately the stiffer ones will not. Herne's Cup and LHO this year I believe allow up to 18kg

While we use more precise scales as part of kit check, if you happen to own a Regenyei Medium (or other sword you're worried about) you can fairly easily test if it is well over or around the cap with a bathroom scale. This won't be as precise, but if you are well over you'll easily be able to tell.

If you're buying a sword, most manufacturers state somewhere on their website how they measure sword flex - if they don't, ask them. 16kg from the crossguard is around 13kg from the pommel *but this is not an exact calculation so borderline swords may be risky*. Do note that if they are subtracting the sword mass you should add the mass back to the sword before making any adjustments.

Now if you've gotten THIS far you must really have found this interesting. A lot of this content comes from my with with Historical Fencing Research, where I am trying to actually study safety in HEMA using empirical tests. I have a future planned experiment to put each method to the test and understand how they correspond to swords actually hurting people. This requires both a lot of time and money. If that sounds interesting to you, please consider heading over to my Patreon or Ko-Fi pages and becoming a supporter:

https://www.patreon.com/HistoricalFencingResearch
https://ko-fi.com/historicalfencingresearch