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  1. Lapedog


    Dec 7, 2016
    Another example I can think of is those Jerry Cans for gasoline. I heard that the X shape stamped into the sides greatly improved the stability of the can walls. Now in that case material was not removed but rather the X shape was stamped in which I guess would have an effect similar to fluting something. Like corrugated aluminum siding.
    R.C.Reichert likes this.
  2. kuraki

    kuraki Drinks Pearl in a can. Knifemaker / Craftsman / Service Provider

    Jun 17, 2016
    Take a piece of tin, or brass shim stock. It's floppy. Bend a crease down the center like a pitched roof. Now it's much stiffer. You've increased the cross section. Now instead of .030 thick, it's maybe .500 tall from peak to base depending how far you creased it.

    You've essentially created a triangle in the material in the axis of the stress. Rather than the flimsy flat with it's two points or lines of stress, you've added a third and moved them apart 5 or ten times their original difference. That distance is like a lever of support.

    I'm not trying to say you can't do this with a fuller as we discussed. If you just move the material into a strategic location like the bend in the shim stock, it has a similar effect.

    I'm trying to describe the scale is vastly different. If you take a .200 thick blade and fuller then upset the spine into a short "t" you'll maybe increase it to .250 or .300 at the most. So rather than increasing the cross section by 5 or 10 times, you've only increased it by 25 or 30%.

    That's why a tape measure acts so stiff, but the simulated blades with fullers and equal mass only showed a small amount of deflection resistance. So yes, similar effect to creases in sheet steel to prevent oil canning, but at a vastly different scale.

    I hadn't even considered the effect that geometry might have on vibration and think that's a very keen insight worth investigating further.
  3. R.C.Reichert


    Jul 26, 2008

    This is what I was trying to describe using the tape measure as an example. Thanks! I think this is why fluted plate armor was so much stronger than non-fluted armor. The ridges add rigidity.
    Last edited: May 18, 2017
  4. MBurks


    Mar 21, 2016
    I'm a musician.

    Best post in this thread.

    Re hammering cymbals is far out.

  5. R.C.Reichert


    Jul 26, 2008
    Perhaps someone should ask a blade of grass this question?...

    AVigil and Lapedog like this.
  6. mete

    mete Gold Member Gold Member

    Jun 10, 2003
    Jerry Cans ? The X is there to prevent "oil canning "
  7. milkbaby


    Aug 1, 2016
    Y'all forgot to mention that a fuller usually adds around three points to tacticoolness rating.
    kuraki and Mecha like this.
  8. Natlek


    Jun 9, 2015
    Maybe this have nothing with subject , but ..............I remember years ago when Honda /motorcycle/ change swing arm ,normal one with two arm with one arm swingarm for rear wheel of course .Normal one have two square AL tube with dimension 40x20mm ,I don t remember wall thickness .For new one arm swing arm they use 80X40mm AL tube with same wall thickness as first one . Even today it s hard to believe to me that they have same strenght ............:)
  9. Matthew Gregory

    Matthew Gregory Chief Executive in charge of Entertainment Knifemaker / Craftsman / Service Provider

    Jan 12, 2005
    All of my fullers add an additional fifteen horsepower with no loss of efficiency.
  10. Lapedog


    Dec 7, 2016
    I heard the Xs stamped into the walls of jerry cans was to make the walls less flimsy. Isn't oil canning prevented by the X because it makes the walls more ridgid.
  11. kuraki

    kuraki Drinks Pearl in a can. Knifemaker / Craftsman / Service Provider

    Jun 17, 2016
    No one is arguing with that?

    Your duct work is creased in an X rather than stamped for the same purpose.
  12. Karl B. Andersen

    Karl B. Andersen

    Jul 27, 2003
    That's completely understandable. Lots of folks understand its origin.
  13. Danke42


    Feb 10, 2015
    They never had the same strength but they traded that off for the ease of tire changes in endurance races. Eventually as the horsepower race continued unchecked even bikes that came single sided in stock form got 2 sided swingarms in the race spec and they resorted other mechanical magic when doing a wheel change at Suzuka.

    And as a note they would all bend/flex but the dual sided ones would flex with less twist so more consistent feedback to the rider.
  14. kuraki

    kuraki Drinks Pearl in a can. Knifemaker / Craftsman / Service Provider

    Jun 17, 2016

    What would be a realistic moment of torque applied to twisting a sword in in/lbs? I've modeled up a sword to simulate twist and just threw 25 in/lb in but I think that's pretty low?
  15. Nathan the Machinist

    Nathan the Machinist KnifeMaker / Machinist / Evil Genius Moderator Knifemaker / Craftsman / Service Provider

    Feb 13, 2007
    That's idiotic Matt. Fullers add fifteen HP per side, so unless you're making single fullered blades it's 30 HP total. And the unit of measure was tacticoolness rating, you have to convert. You twits need to learn basic math. *sigh*
    milkbaby, Beanman13, Lapedog and 4 others like this.
  16. Matthew Gregory

    Matthew Gregory Chief Executive in charge of Entertainment Knifemaker / Craftsman / Service Provider

    Jan 12, 2005
    I measure all my fullers in brake horsepower, not your inflated gross ratings. This is all about real-world performance, not your phony CNC horsepower.

  17. Mecha


    Dec 27, 2013
    According to this guy's excellent article, the answer is easily calculated yet pretty much impossible to determine! :D


    I am NOT good at math, and really don't know how to estimate how big the spike in torque on a sword blade could be, let's say, if one was cutting a huge standing bamboo and made a nasty mis-cut. That energy has to go somewhere. I would guess it could be as high as 100 ft/lbs.

    May I ask, is the sword blade in your simulation distally-tapered?

    Also, I found this interesting little article scouring around and thought it was worth a read:


    Even though it doesn't really compare to what's going on in a sword blade, this calculator says that a half pound moving at 80 mph translates to just over 100 ft/lbs of force; I'm sure a sword blade can exceed that by a lot. The concentration of power on the thin edge is insane! And the aftershocks run all through the long blade. I have seen a few super slo-mo videos of swords cutting, and they can whip and twist all around in a serpentine fashion although with the naked eye in real-time they appear to stay rigid, similarly to an arrow shaft when the arrow is released.
    Last edited: May 19, 2017
    Lapedog likes this.
  18. kuraki

    kuraki Drinks Pearl in a can. Knifemaker / Craftsman / Service Provider

    Jun 17, 2016
    There is distal taper in the last third of the blade. 28'' long from the guard, .25 at it's thickest, wide fuller tapers with the edge. Just under 2'' wide at the guard to just over 1.5'' before the tip, 1.8 lbs without guard or handle.

    I thought you were talking about twist axial to the length of the blade. I agree the forces you mentioned can be incredible.
  19. Mecha


    Dec 27, 2013
    Yep, twisting along the length. The hilted end would be held with two hands (like a moving clamp), and let's say that a spot 10" back from the tip is cutting through something relatively hard and tough when it's deflected and twists between the catch-point and the hands. I was thinking that a big fuller could weaken a blade in that regard and more easily take a twist.

    It would be fun to test a few real-world examples with a torque wrench, or better, something that impacts the long blade at a bad angle: find out how much it takes to twist the blade. :)
  20. kuraki

    kuraki Drinks Pearl in a can. Knifemaker / Craftsman / Service Provider

    Jun 17, 2016
    Ah gotcha. My biggest problem with realistic simulations is the limited material library. I haven't discovered how, or, if it's possible, to add or customize the materials available to get something that more closely represents hardened blade steel. Everything in there acts like annealed material.

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