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  1. Mecha

    Mecha KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Dec 27, 2013
    Ahh, crazy. I was wondering about that. When it comes to this sort of stuff, quantifying the ultimate "feel" of a blade and how the various distal tapers, grinds, or fullers (and heat-treatment) affect performance for a task, I often just follow intuition, assume the resulting observations are real, and then try to figure out "why" after the fact. For example, beating big blades into targets at really bad angles a lot just to see what happens, 'though it looks really dumb in youtube videos LOL! :D


    I mean, of course a fuller will affect how a long bar of metal twists, but the question is, how severely.
    kuraki and Matthew Gregory like this.
  2. Lapedog


    Dec 7, 2016
    I've watched videos of all types of things being dropped on the ground or an arrow fired from a bow, swords cutting through things.

    The most well known is the arrow. Watching it in slow motion is very dramatic. It reminded me of an eel swimming through water.

    Another one I'll never forget was the cell phone being dropped on the ground. This was in the day of flip phones so I'm not sure how the glass on a smart phone would change ridgidity. Anyway they dropped the phone on the ground and it twisted and bent like it was made out of rubber. I couldn't believe my eyes. I thought if I was to torque and twist my phone that much by hand surely it would break.

    The point is when you watch some of these "ridgid" objects in slow motion it is shocking how much they deflect and twist to absorb force.
  3. Danke42


    Feb 10, 2015
    kuraki likes this.
  4. kuraki

    kuraki Drinks Pearl in a can.

    Jun 17, 2016
    It's giving 4.48nm for twisting a door knob which is the motion I'm thinking of, that converts to 40 in lbs. But I still think you're right on tripling it as those strength tables tend to be closer to average than exceptional. In nursing school they had us doing physical capability studies using similar charts. I remember ours had a range, and for male grip strength upper percentile was listed as 100 ish lbs. I could peg the dynomometer at 180 lbs and I bet anyone here who does much forging or other physical labor could too.
  5. Danke42


    Feb 10, 2015
    I"m thinking the twisting off a jar lid is more like someone getting a blade stuck and trying to yank it out.
  6. Mecha

    Mecha KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Dec 27, 2013
    Yes, and since a sword grip can be twisted in the hand during a deflected strike from whatever happened on the business end, then the forces upon impact that run through the blade must be nuts, not that I advocate beating your sword into solid heavy objects. :D The fuller effect is certainly at play here.
  7. mete

    mete Gold Member Gold Member

    Jun 10, 2003
    I'll bet the guy in the video is a nice calm relaxed guy after working out frustrations !!

    Arrows and spears do wiggle as they fly but will calm down as the go farther. That's because you drive them from the back.. There was a job here to stabilize a dirt bank with rods .They used a method of driving them from the front !! The rods penetrated the soil very well which would not happen if they drove them from the back !!

    There was a very nice photo of a broken knife [ on this forum IIRC ] .Lot's of excuses but experiences in failure analysis made it easy for me to tell the story. Not the knife at all but the user , batonning, put he blade in the wood, then giving the blade a twist !!

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