6 ms·

Why not? To me (a layperson in the physics of helmets and brains), they would seem to be quite directly related, especially when the cause of the gees is not re

• ashtonkem 6y ago
  Helmets are padded, deform, or have suspension systems to decelerate any impulse that the helmet takes. This should cause a very different g-force spike between what the shell of the helmet experiences, and what the wearer experiences. If the helmet didn't decelerate any impulse to the head, the range of impacts that it could theoretically protect the wearer from would actually be quite narrow.
  • frutiger 6y ago
    > If the helmet didn't decelerate any impulse to the head, the range of impacts that it could theoretically protect the wearer from would actually be quite narrow. This is wonderful understatement: “If the g-forces between the helmet and the brain weren’t different, the helmet wasn’t a helmet at all!”
    • djmips 6y ago
      A helmet can just protect the skull So a helmet doesn't have to be padded or help with g-forces to be a helmet. I think helmets were initially just to prevent skull fracture.
      • bryanrasmussen 6y ago
        well, yeah when those helmets were worn by knights in the middle ages, but many helmets nowadays have to withstand g-forces to do their job. If English was like Italian there might be a specific word for a non g-force withstanding helmet and otherwise.
        • willis936 6y ago
          And every war in the first half of the 20th century.
        • ashtonkem 6y ago
          Knight's helmets were actually heavily padded, with most knights wearing heavy padded linen garments over their torso, arms, and head. Nicer helmets would have a leather strap system as well. Many helmets appeared to have integral liners, although the linen has rotted away and only left the rivets where they were attached. With the advent of plate armor, offensive techniques began to focus on concussive force in order to disable combatants, including war hammers and maces. A blow to the head with only a bit of steel between your skull and a mace would be a fatal experience without any padding. Even with padding it was notorious for deafening and disorienting knights, due to noise and (presumably) brain injury.
          • bryanrasmussen 6y ago
            It's a lucky thing that Sir Ulrich Von Liechtenstein was such a cunning champion in both the sword and joust or he might have ended up with all the brains of poor Wat.
    • ashtonkem 6y ago
      A helmet without padding can protect against low energy penetrating impacts; think BBs or similar. They do this by spreading the impact point out over the entire head; preventing penetration or fracture. But for pure G forces, you’re right. A helmet with no padding is effectively similar to not having a helmet at all.
• pengaru 6y ago
  The helmet is padded. Your head is in a suspension within the helmet, much like your brain is in a suspension within the skull. Your skull can accelerate at extremely high G's without harming the brain as long as it stays well within the modulus of the suspension. i.e. not for too long. The helmet adds another suspension on top of this.
  • vaidhy 6y ago
    You are confusing the ability to sustain the g-force by the brain with the force experienced. A padding on the helmet helps in event of collision, not the g-force which is due to the acceleration
    • pengaru 6y ago
      How is a collision not just another acceleration?
      • amluto 6y ago
        In a collision, the helmet gets hit and, subject to some degree of padding and such, transfers the impact to the head. If you’re sitting in a sled and the sled accelerated rapidly, your head and your helmet must accelerate with it, although you may not perfectly track its path. Unless the helmet is also secured to your torso, all the forces on the helmet come from your head. You would need tremendous acceleration of your head to meaningfully deform any but the softest padding.
    • refurb 6y ago
      Sure the helmet helps with g-forces. Say you're going down the track and enter a tight turn. The helmet contacts the side of the sled at say 5 g's because the helmet is hard and so is the side of the sled. The brain impacts the helmet, which impacts the side of the sled, but the padding in the helmet spreads that impact over a greater period of time, since the padding compresses, so the brain only experiences a g-force of 2.
• etrautmann 6y ago
  The helmet is a light mass, which can move relative to the head, and experience drastically higher g-forces for very short times. Sampling an accelerometer at kHz rates as a helmet is vibrating (without translating all of the vibrational energy into the head), will measure larger peak G's than the head experiences. For this reason, when studying head impact for football players, they mount the accelerometers in the mouth guard. This more accurately reflects the real g-forces, as the teeth (ideally) don't move much relative to the brain during an impact, and have the appropriate reference frame. The differences can be extremely large. The peaks reflected in this graph are absolutely not real and should not be taken literally.
  • willis936 6y ago
    What would you say is the maximum frequency that the helmet is coupled to the head at? Filtering is a trivial operation and I would expect the g forces felt by sledders to be sustained for the better part of a second. You lose a lot of fidelity, but if you’re still over the line then you know there’s a problem.
    • mrfredward 6y ago
      According to the article, the tracks are designed for sustained g-forces of 5Gs. These are the accelerations that are sustained for greater than a second. According to the annotations on the NYT's plot, the g forces which are most alarming are from when the helmet makes contact with the ice. This is precisely when the helmet accelerations would be expected to differ wildly from what the head is actually doing. A low pass filter could easily be used to remove the impacts with the ice, but minus the impacts with the ice there's nothing in that acceleration trace that should be alarming for a professional athlete. The high frequency content is the concern here.
  • mam2 6y ago
    That sounds like r/imsosmart ... a simple low pass filter would be sufficient to negate the effects you talk about
    • 6y ago
• alephu5 6y ago
  The whole point of a helmet is to absorb impacts. It's designed to dampen rapid accelerations so your head doesn't have to.