Fencing Mythbusters: Bending Blades
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- Опубликовано: 1 мар 2023
- I'm something of a scientist myself...
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I think the difference between bending by hand or under your foot is not so much the friction temperature. It is just that you keep the bending angle small if you bend it under your foot. Pulling on the blade may help to increase the tension on the outside part of the blade too. But that effect will be very small too and may even help cracks grow in that side of the blade.
This is my first thought as well - bending by hand when holding the guard in one hand and somewhere near the point with the other seems likely to get more of the force localised in one area, with the potential to break being higher. When you run it under your foot to straighten it, you're bending it over a longer distance, more blade area getting less force. This might mean the effect is better for straightening a curve than a sharp angle, but TBH once it's made a sharp angle it's maybe not recoverable anyway.
Straightening a blade under your foot is safer. I was making this point in a beginner class, stating that if someone bent a blade please ask me for help and that under the foot is safer. Student proceeded to bend a blade in an action and then quickly tried to straighten it himself. The blade broke right at his thumb, causing a gash that took the rest of class to stop the bleeding and bandage. Better to have it break between a shoe and the floor than against a thumb or palm of the hand. Another reason not to run your bare hand on the blade is the possibility of metal splinters. As the blades impact each other, they are shaving bits of metal off the blade and possibly causing micro cracks (future possible break points) this is the reason that using a towel before handling a blade is suggested.
Correct, the "bending angle" is the key. If you bend by hand, you are much more likely to over-bend it and to then have to bend it back. These cycles of bending the material back and forth just mean more total plastic deformation/bending and this causes material fatigue. Also, indeed, steel gets more brittle in the cold, it's a know mechanical engineering issue. I've seen a guy snap the blade on a forklift in very cold temps like this. It can literally break like glass. Yes, this is an anecdote and should not be taken as a general rule but there it is...
I use my foot to apply more force to a smaller section of the blade and bend the really bad kinks. Smaller adjustments with the hand. Not that I ever thought about it. Just from experience.
So here is basically what I was taught. As far as "heating" the blade, it's not so much about making the blade easier to bend as it is about preventing making cracks in the steel. If the metal is cold, like form leaving it out in the car during winter, you are more likely to form small micro cracks in the blade when you bend it which would lead to blade breaks. As for using the foot instead of the hand, obviously you can use more force with the foot, but more importantly, you don't have the risk of getting metal splinters in your hand.
this experiment seems more robust and self-aware of its limitations than those of some published research papers. Nice topic, nice video 👍
Fencing Mythbusters... intresting, would like you to make more of these:)
This is the first time I've heard of this. Our belief is that so the blade doesn't snap and that if u bend without ur foot it snaps. Coming from experience it snaps doing it without ur foot.
I have only ever seen a blade snap being bent by hand and never by foot
Interesting experiment. Though I think something is missing. I’m a longtime fencer and coach (28 years now).
Using my shoe and the floor I can straighten blades in often one, sometimes two passes.
I straighten while passing between the foot and the floor with heavy pressure.
Straightening cold in my hands takes a lot more time flexing and bending the blade.
I’ve also used a wrench to fix small bends or side to side bends. That works pretty well with a cold blade.
You should make one on how to maintain a blade that rusts and the difference between brands (on blades) like allstar vs leon paul blades
I agree about the temperature being irrelevant (unless you have jittery hands in a freezing cold fencing salle and overbend your blade!)... or live near the artic circle.
The difference in strength of maraging steel (18%Ni) is a decrease of 3% between 0 degC and 50 degC and 2% between 10 degC and 35 degC. It's brittleness is not going to change much either... that's why we use maraging steel. It is not brittle and it's brittleness doesn't change over time and not substantially with temperature.
The cheaper carbon steel does develops micro cracks, but you'd have to live in the Arctic Circle for the cold to affect the blade ductility. I'd think that the reason you use a towel or your foot in that case is to stop your hand freezing to the blade!
I've broken a few while straightening them over the years, but it's usually because it has a kink in it and I get over-enthusiastic. I do straighten them by hand and not foot, but one of the risks of using your hand is steel splinters. If you want more control, use the "ring spanner" method (or the handle of a large crescent wrench).
I've just been straightening a brand new maraging foil blade that developed a kink the very first hit. In my experience this blade is now toast, it's just a question of when. I can still see the point of inflection of the kink, but have given the rest of the blade a nice arc either side to hopefully compensate and overcome any tendency to kink again, but.... I used both a ring spanner and my hands (no feet) and it took about 20 mins of gentle but firm bending both sides of the kinked area.
I'd be interested to know if this kink was due to a defect in the blade or just bad luck (or both). I've had it happen once before, many years ago, and I'd think it's a defect in the blade.
As a lifetime fencer and mechanical engineer I applaud your curiosity and experimentation. But my conclusion is that you focused no the wrong aspect of blade straitening. The diffnece between bending the blade in your hand vs sliding it under your foot while pulling upwards has to do with concentrating the strain in one point (hand) versus distributing it over a wider length of the blade (foot).
Here's how to 'properly' straighten a blade. Get yourself a small box wrench (they sell these for 50 cents at Goodwill or other thrift stores). Put the blade through it. But DON"T try to straighten the bend all at once.... move it to several spots above and below the bend and apply a small amount of torsion with your wrench. The wrench gives you so much mechanical advantage that you can easily put 6 or 8 small corrective bends that nullify the horrible bend you're trying to fix. This way you never really strain the steel into the plastic zone and you're "it might break!" bend is easily repaired.
I learned this from Dave Micahnik the long time coach at Penn 40-45 years ago when we were on some international trip together. It's never failed me since.
I just use a ring wrench to bend my blades back. Only ever broke one blade that way and that one had a ninety degree bend in it, so its days were numbered anyway. I never bother to heat them up first.
Nice
Observation. I believe your experiment is off track from the get go. You are measuring the flex of the blade at different temperatures. There is no reason to expect it would shed much light on the physics of straightening a bend in the blade. Straightening a bent blade is about the geometry of the force applied.
In an earlier comment Edwin nailed it. You put it under your foot so it *won't* flex, and will *bend* at the desired point to straighten it. Heating the blade a little before bending it also facilitates the bend. But that is secondary to modulating the flex and isolating the bend.
Even if temperature had absolutely no effect on the process, straightening your blade under your foot is the way to go.
For what it's worth.
Well, if the Flash was a fencer it would make a difference I think.
I am pretty wary of bending foils and Sabres with my foot unless it's some ridiculously large attack in prep kink. Micro adjustments between the two thumbs to get a consistent contour is the best method generally in my experience and is much less likely to crack the blade. I've almost never snapped a blade by hand, but by foot, even with a shallow angle.. It's a real gamble.
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