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Technology Science

Building a Better Bike Helmet Out of Paper 317

An anonymous reader writes "Inspired by nature, a London man believes the solution to safer bike helmets is to build them out of paper. '"The animal that stood out was the woodpecker. It pecks at about ten times per second and every time it pecks it sustains the same amount of force as us crashing at 50 miles per hour," says Surabhi. "It's the only bird in the world where the skull and the beak are completely disjointed, and there's a soft corrugated cartilage in the middle that absorbs all the impact and stops it from getting a headache." In order to mimic the woodpecker's crumple zone, Anirudha turned to a cheap and easily accessible source — paper. He engineered it into a double-layer of honeycomb that could then be cut and constructed into a functioning helmet. "What you end up with is with tiny little airbags throughout the helmet," he says.'"
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Building a Better Bike Helmet Out of Paper

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  • by dbIII ( 701233 ) on Sunday January 12, 2014 @09:16PM (#45935157)
    I'd say it's the article at fault not the designer, but the reason polystyrene foam is already used in bike helmets is exactly the same - "tiny little airbags throughout the helmet".
    I wonder how this compares? Does this absorb more energy?
    • by arielCo ( 995647 ) on Sunday January 12, 2014 @09:51PM (#45935425)

      If I had to guess I'd say polystyrene is slower to compress and returns some of the energy (elastic deformation), while cardboard tends to deform permanently, absorbing all of the energy. As for being "disposable", I've read that conventional helmets should be discarded after an impact; these make sure you do.

    • by Jarik C-Bol ( 894741 ) on Sunday January 12, 2014 @10:06PM (#45935529)
      if you bother to read the article, you would learn it absorbs far more of energy. They state that a 15mph crash can subject the brain to 220G of force wearing a polystyrene helmet. Using the paper helmet, the test units brain-analogue was subjected to a mere 70G of force. This was tested in Europe, where regulations state for a helmet to be approved, the brain may not be subjected to more than 300G of force at 15mph. So a significant improvement over traditional polystyrene helmets, in terms of energy absorption and dissipation. I posit that this is most likely due to the fact that paper does not recoil back to its original form as much as the polystyrene.
      • Maybe the NFL should consider this for the longstanding concussion problem that's been getting a lot of publicity lately. They could afford to throw them away as often as needed.

      • "G" is not a measure of force OR energy but instead translated into units of acceleration. It helps to answer a question with something related before criticising the person asking it.

        The important thing in this case is the energy absorbed - which can be derived from the relationship between force and displacement and not just one of those. So it's related to the area under the force versus displacement curve (or directly found from the area under the stress strain curve). Or you could just hit it with
      • by Solandri ( 704621 ) on Monday January 13, 2014 @12:40AM (#45936471)

        They state that a 15mph crash can subject the brain to 220G of force wearing a polystyrene helmet. Using the paper helmet, the test units brain-analogue was subjected to a mere 70G of force. This was tested in Europe, where regulations state for a helmet to be approved, the brain may not be subjected to more than 300G of force at 15mph.

        15 mph = 6.7 m/s. 220 Gs = 220*9.81 m/s^2 = 2158 m/s^2. To generate 220 Gs decelerating from 6.7 ms, you need to decelerate in 6.7 / 2158 = 0.003 sec.

        At a constant deceleration, that's a distance of v^2 = 2ad, or d = v^2 / 2a = (6.7)^2 / (2*220*9.81) = 0.0104 meters = 1 cm.

        To generate 70 Gs, you need to decelerate in 6.7 m/s / (70*9.81 m/s^2) = 0.0098 sec.

        At a constant deceleration, that's d = v^2 / 2a = (6.7)^2 / (2*70*9.81) = 0.0327 meters = 3.3 cm.

        I posit that this is most likely due to the fact that paper does not recoil back to its original form as much as the polystyrene.

        The speed at which polystyrene springs back is so slow you almost need time lapse photography to watch it (crush a styrofoam coffee cup and see how long it takes to uncrush itself). The decreased G forces are entirely due to the distance the structure collapses. Polystyrene is a stiffer, closed-cell material with limited deformation due to the cells resisting popping (indeed, breakage is usually due to adjacent cells shearing apart, rather than the cells popping). While cardboard is essentially open cell and more likely to collapse its entire thickness.

        That's a double-edged sword though. The cardboard helmet is more likely to be ruined or structurally compromised from lesser impacts, like having the bike fall on top of it while you're transporting it in the back of your truck. Stuff the polystyrene helmet can survive because such impacts do not have sufficient force to pop the cells or shear adjacent cells. The air in the cells just gets compressed more, and springs the cell back to shape once the load is removed. Since the cardboard is open cell, it has to rely entirely upon the paper's ability to spring back to shape to survive such loads intact.

        And (judging from the pictures) if you hit at the wrong angle, you can cause the cardboard to collapse by twisting and falling over rather than crushing, thus greatly reducing its protection. Standardized tests are great in that they're reproducible, but they suck because by always testing in the exact same manner you allow designers to optimize for the test instead of for real-life conditions. i.e. You can improve performance in tested orientations by reducing crash protection in non-tested orientations. The more solid structure of polystyrene allows forces to be better transmitted between cells thus helping even out its crash protection at all orientations. The cardboard helmet looks like it's traded off that uniformity for anisotropic crash protection which peaks in the orientations which are being tested (longitudinal and transverse). A better design would mesh the cardboard into triangles, not squares. Squares are notorious for collapsing without using any of the structural material's innate strength. It's why the most common fiberglass weaves are 0/30/60 degrees, or 0/90 layered at 30 or 45 degree increments so you're not putting all your strength along just 0 and 90 degrees like this cardboard helmet does).

    • Yes, FTA, this absorbs 4 times more energy in a typical collision than a styrofoam helmet.

    • Re: (Score:3, Interesting)

      Aluminium honeycomb is used as a single-use shock absorber and deforms very evenly and I imagine that the same thing is true of this paper stuff. It's fairly impressive, but is best seen in an image: [].
    • Shhh... don't ruin his new business with facts. The UK economy has enough trouble getting going as is.
  • by Todd Palin ( 1402501 ) on Sunday January 12, 2014 @09:18PM (#45935177)
    Paper had one characteristic that might make it less than suitable for use in rain. One foam helmet might be cheaper in the long run than a bunch of soggy paper helmets.
  • by Picardo85 ( 1408929 ) on Sunday January 12, 2014 @09:19PM (#45935185)
    The name is Hövding and it's an "Airbag bicycle helmet". It's developed by some team in Skåne, Sweden. Looks really cool. []
  • "It is well documented our enterprise patented and manufactured paper made from bicycle helmets."_tm.
  • One word says it all, "rain."

    • A second word negates your first word.

      • Re:Rain (Score:5, Insightful)

        by RobertinXinyang ( 1001181 ) on Sunday January 12, 2014 @10:37PM (#45935751)

        I actually thought about that. However, there are very few cost effective methods of waterproofing paper that work. Think of the waterproof corrugated paper packaging you have seen. It is fine for short exposure; but, it does not hold up to prolonged immersion and exposure.

        A bike helmet will sit in puddles; it will spend hours in downpours. If you waterproof for the exposure conditions that bicycle helmets see, at some point it ceases to be paper.

        • by Ksevio ( 865461 )
          Stick it in a plastic bag and it should have all the same benefits plus being waterproof. I'm sure the manufacturers could come up with a way that lets air through if they wanted that.
  • by craighansen ( 744648 ) on Sunday January 12, 2014 @10:18PM (#45935609) Journal

    I think you have to read between the lines carefully to find the real value in the article. I think it can be equally valid to build a bicycle helmet from corrugated or expanded cardboard as is is with styrofoam + shell. (OK, styrofoam is a trademart for Expanded Polystyrene.) As others have commented, cardboard is suseptible to damage from moisture, so it has to be sealed against it. In addition, I'm not convinced that the cardboard design is cheaper to manufacture than the styrofoam designs.

    To me, the relevant signal is the reduction in maximum G force. The article suggests that the design limit is 300G, and conventional helmets achieve 225G - while his design gets to 70G. Presumably, the mechanism for doing that is to absorb the impact energy over a significant period of time before transmitting the forces to the wearer. Given the velocity of the collision, this means that the helment has to be built with a greater distance between the outside and inside of the helment than existing designs. If people are willing to wear thicker helmets (appropriately designed), such helmets could be reasonably expected to perform better - I'd think comparable designs could be easily built from the styrofoam + shell technology that's commonly in use.

    Finally, the inventor says he was inspired by observing that his helmet was broken in the collision. THAT'S WHAT THEY ARE MEANT TO DO. In absorbing the forces of the collision, the helmet is permanently deformed. If your head is saved from destruction by a helment - buy a new helment to replace it.

    • Please sed -e 's/helment/helmet/g' to the above.

    • Why would you assume that absorbing energy more slowly implies that it's thicker? Simply absorbing more energy per unit time would do this too (as it would rapidly slow the deceleration, and hence extend the period of movement).

  • by nixkuroi ( 569546 ) on Sunday January 12, 2014 @10:42PM (#45935781)

    After RTFA, it seems that the most obvious material to make the helmet from is woodpecker skulls. Didn't anyone else get that?

    • by PaddyM ( 45763 )

      The article? I thought it was obvious from the summary, but the solution: separating our forehead from the rest of our skull with woodpecker cartilage, did not seem like a real option. Maybe these were the prosthetic foreheads everyone was talking about in that They Might Be Giants song?

  • by hubie ( 108345 ) on Sunday January 12, 2014 @10:53PM (#45935851)
    Corrugated cardboard has been used for decades under high-altitude scientific balloon payloads to absorb the impact of landing from a parachute descent. You don't have to put too many of them under several thousand pounds of experiment and gondola. Here [] is a (not so good) picture of one example. The cardboard provides a very nice low-gee impact.
  • I'm all for a better designed bicycle helmet, and I'd use it in some circumstances. But I'm vehemently against the government mandating that I must wear one.

The intelligence of any discussion diminishes with the square of the number of participants. -- Adam Walinsky