Building a Better Bike Helmet Out of Paper

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.'"

Comments

Tiny little airbags like the polystyrene foam?

[dbIII]

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?

Re:Tiny little airbags like the polystyrene foam?

[Solandri]

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).

Re:Bike helmet?

[gnoshi]

I hate to say it, but my impression is that linking to http://cyclehelmets.org/ for issues of helmets is like linking to WUWT for issues on climate change. It has a particular position, and runs with it (whether that is intentional or not). They are by no means unique in this, and are also not the only position in the discussion to do it.
That said:
1. Dumb cyclists will be dumb, and if someone rides less cautiously because they think a helmet will protect them they are dumb
2. Dumb drivers will be dumb, and if a driver is really driving less cautiously around a cyclist on the basis that a helmet will protect the cyclist they are not only dumb but outright dangeous
3. Crossing the threshold with 100% of the force is still probably going to be more damaging than crossing it with 50% of the force (if 50% is absorbed by the helmet)
4. And many are caused by non-rotational impacts, which helmets reduce
5. Dumb cyclists are dumb, and if the pool of cyclists is largely made up of dumb cyclists then that doesn't mean helmets reduce safety, just that if a bunch of less dumb cyclists were added to the pool they would dilute the apparent stupidity of the group overall. Not saying cyclists are stupid, but rather that the number of stupid cyclists is the same irrespective of whether it is 100 stupid cyclists in 101 total cyclists, or 100 stupid cyclists in 1000 total cyclists.
6. If #5 is in fact true (and there is little agreement on it) then this is true, and indeed having more cyclists on the road very likely does make it safer for all cyclists.

There in another arguments for not requiring helmets, also based on the idea that requiring helmets reduces the number of cyclists: even if helmets do reduce the likelihood of death or brain injury in an accident, the advantage of improvement in overall community health as a result of more cyclists offsets the disadvantage of a subset of these being dead or brain injured.

Re:Bike helmet?

[Anonymous Coward]

Also, 4) many severe head injuries from cycling crashes are caused by rotational forces, which helmets can exacerbate. 5) helmet requirements almost universally reduce the number of cyclists (or reduce the growth in cycling), leaving the cycling pool with more adventurous and risk-prone bikers; 6) corollary of #5, fewer cyclists means less road time experience between cyclists and car drivers.

See http://cyclehelmets.org/.

You're just trying to rationalize your personal dislike for helmets.

Saying helmets don't protect your head is like saying water isn't wet. It's fucking risible. Trying to prove helmets don't protect by using statistics from different groups (cyclists who wear helmets are a different type of rider from cyclists who don't) smacks of desperation.

Tell you what. I get to smack you upside your granite skull with a car door. You can put on a helmet or not. Your choice.

But the brain damage has already been done.

Re:Bike helmet?

[jeffb (2.718)]

Why do these arguments sound so familiar? Probably because they're so similar to the arguments people used to make against seat belts.

"They'll increase accidents because they make it harder for drivers to stretch and look around!"

"They'll trap me in a burning or sinking car!"

And, my all-time personal favorite (yes, I've actually heard people say this):

"They'll prevent me from being thrown clear of the collision!"

People will persistently find the very stupidest reasons for not doing something that bugs them. Yes, each of these eventualities might have killed a few drivers who would've been spared if not for their safety belts. But those numbers are absolutely dwarfed by the number of lives saved and serious injuries prevented.

I've only been in one significant bike accident, and I was lucky enough in that one that my helmet didn't come into play. But looking back at the accident and the pattern of my injuries, I can't explain how the helmet was spared. I sure as hell am not tempted at this point to ride out without it.