How Does a Bike Helmet Work?

According to the National Helmet Safety Institute, you can’t buy better protection for your brain than a bike helmet. But you might ask the obvious question – how those bicycle helmet work.

Let me tell you what I uncovered from my research:

Bike helmets are designed and manufactured in a way that a layer of foam, which is the hard shell, is designed to spread the force of an impact over a broader area, so when the foam is crushed, your skull will not fracture. There is also a softshell which is meant to squeeze inward and absorb the impact energy.

These amazing chapeaus may not be the most stylish headgear on the planet, but after all, how stylish is an ER stay for an injury that could have been avoided had you just worn a helmet?

Not to mention they’re obligatory to wear in some states in America.

From the moment of impact, the human brain responds to what is likely a “violent rotation of the head.”

But, because your brain is wired to stay stationary, chain reaction results that impact blood vessels and nerves throughout the brain, which is designed to stay in one place and not move.

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In order to mediate extreme movement, bike helmets are manufactured with crushable foam rubber materials that are installed within the helmet’s shell. At the moment of impact, the foam crushes in reaction to the blow.

What’s the science behind this? Energy is disbursed and the collapsed foam impacts the brain’s movement by what the NHSI calls “six-thousandths of a second (6 ms).”

Sound like no big deal? That quick sequence is long enough to reduce some extreme brain impact and rotation, too.

Photo by Abdou Mrehouri on Unsplash

Engineering is everything

It’s no secret that the thicker the foam used to line bike helmets the better the chance it can mediate some damage done to the brain during a bike crash. That’s why shoppers should look for the most amount of it.

You don’t have to study physics to realize that if your helmet is lined with 30mm of foam, your head will fare better than it would have had your helmet been lined with only 15mm of the stuff.

Does the density of that foam matter? You bet. According to the NHSI, scientists are working assiduously on “miracle” foams that meet what’s called “ideal rate sensitive” standards. “

The ideal “rate sensitive” foam would tune itself for the impact, stiffening up for a hard one and yielding more in a more moderate hit,” say those working on this project.

Are there trade-offs?

The answer is yes. Thick helmets may not benefit the head’s outer circumference and if the exterior material doesn’t promote “skidding,” the head could be wrenched enough to cause neck strain and, at the most extreme, subject the brain to rotational forces, making the super-thick helmet a less than ideal choice.

Cyclists cite “comfort” as a major reason for choosing one helmet over another, but shoppers risk injury if they pick one with what NHSI calls “squishy fitting pads inside the helmet.” Tests onliners not attached to outer skins prove this type of liner can be ineffective at protecting the head-on impact.

Rather than helping slow down the rate at which the head jerks around, these non-attached pads simply collapse, leaving your grey matter to fend for itself.

Another interesting that we’ve discovered recently is the Dutch don’t wear helmets. Do you wonder why? You can find out in our article about the Dutch helmet facts.

Do you have long hair? We’ve got some tips on wearing a helmet with long hair.

Should you wear a helmet that’s been in an accident?

Nobody wants to spend good money to replace a pricey helmet, but even small accidents can damage the interiors of helmets and you might not even know it. When a polystyrene helmet is in an accident, the foam collapses and the helmet is no longer safe to wear.

That’s why parents regularly shop for helmets engineered to be worn by hockey players and skateboarders. And just because the shell remains intact, that doesn’t mean the interior suspension is intact, either.

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