Comments on: Ribcap helmet beanie in the US

Question: Ribcap helmet beanie in the US

hokie409 — Tue, 05 Dec 2006 18:09:30 -0800

Can I buy a ribcap in the US?

I just learned about this beanie that hardens when you fall:

Ribcap

Can I buy this in the US at a store or website w/o using this Canadian site? I read that it would be available in the US already but I could not find it anywhere.

By: MonkeySaltedNuts

MonkeySaltedNuts — Tue, 05 Dec 2006 18:29:27 -0800

Amason has ribcaps

By: nicwolff

nicwolff — Tue, 05 Dec 2006 18:34:39 -0800

Huh, when did Amazon get them? I also looked for a US vendor just last week, but gave up, and ordered one from the Canadian site. And got screwed on the exchange rate. I wonder if it hasn't shipped yet, and if they'd cancel the order...

By: hokie409

hokie409 — Tue, 05 Dec 2006 19:10:33 -0800

Thanks.
I noticed that the Amazon site says "Usually ships within 1 to 2 weeks. Ships from and sold by Epyx Mountainboards Inc."

And that company is also from Canada.

By: ikkyu2

ikkyu2 — Tue, 05 Dec 2006 20:24:38 -0800

You're aware that the behavior of this material is exactly the opposite of what you want to have happen to your head in an impact, yes? You want a soft material to absorb and distribute impact energies, not a rock hard material that transmits the impact force unmodified to your skull.

By: cadjez

cadjez — Tue, 05 Dec 2006 21:16:53 -0800

ikkyu2, you are correct that something that is rock hard would transmit impact force through it, but this is NOT how d3o works. To understand, first you must realize that d3o is not a single layer of molecules. It is 1/4" to 3/8" thick in the Ribcap beanies and has molecules throughout. Upon impact, the molecules on the outer edge of the d3o padding receive the most force and lock together, absorbing and dispersing the force over a wide area. Now less force is left to be transmitted to the molecules in the inside or core of the padding. These inner molecules lock together less dramatically (the material does not harden as much) as they have received less force from the impact, however they do harden more than their original state and the force is again absorbed and dispersed over a wide area. Finally the molecules on the inner side of the d3o padding (against your head) receive much less impact and therefore the material hardens much less. They still absorb impact, but the material remains relatively soft in comparison to the outer molecules.

This is similar to how a helmet works. A helmet has a hard outer shell with softer, inner padding. Most helmets will have three layers: a hard outer shell, a medium density foam, then soft, low density foam against your head.

It should be noted that drop tests have been done on d3o to prove that it absorbs and disperses force better than any other material currently used in protective sports equipment. Watch THIS VIDEO.

By: allen.spaulding

allen.spaulding — Tue, 05 Dec 2006 22:32:10 -0800

I take it cadjez works with d3o some capacity, which is totally fine. Thanks for the perspective and welcome to the filter.

By: ikkyu2

ikkyu2 — Wed, 06 Dec 2006 00:24:13 -0800

Well, that's good video, cadjez. Why haven't they submitted it to some independent agencies for testing? They're very careful on their website to point out:

Ribcap was not created to compete against helmets. Ribcap's goal is to offer a safe alternative to athletes that refuse to wear a helmet for their particular activity or sport.

..If you are participating in a sport of high-risk that requires use of a CSA helmet, please use a CSA-approved helmet.

By: Chuckles

Chuckles — Wed, 06 Dec 2006 02:55:05 -0800

Now less force is left to be transmitted to the molecules in the inside or core of the padding.

It can not reduce the force. You are arguing that it distributes the force over a larger area. That is a good thing, but perhaps not really significant..

In my understanding of the physics of collision, there are two issues. Blunt impact might crack the skull, but just as important, your brain slams against the inside of your skull.

A typical bicycle helmet consists of a hard shell, an energy dissipating hard foam, and comfort padding. My understanding is that the shell exists only to hold the foam together. Without the shell, the energy absorbing foam would just crack and move out of the way of your head, making it useless. The energy absorbing foam is designed to shatter (pulverize?), just like the nose of a Formula 1 car, as your head slams into it.

Which brings us to the real issue..

It is 1/4" to 3/8" thick

Bike helmets have 1"+ of hard foam because that is how much space it takes to decelerate your brain safely.

Let me explain.. Presumably, the safety standard has a speed of impact rating, and an acceptable brain acceleration rating. Given those two numbers, you design an energy absorbing material which will begin to shatter below the maximum brain acceleration number. Now you have a problem.. Sure, it's shattering, but you have to keep shattering until the brain has stopped. The only way for that to happen is more space. That means there is an effective minimum on helmet thickness, no matter what material you use.

I'm not saying this to endorse helmet use, or to claim that these products are useless. For example, they may well be great for protecting the skin and bone of your head. When it comes to preventing concussion, I suspect they don't do particularly well, and that is the primary reason for helmet wearing.

This is all a common sense interpretation of the physics involved, I'm happy to be corrected.

By: footnote

footnote — Wed, 06 Dec 2006 08:29:44 -0800

Wow, a beanie with molecules! Yay!

Come on people, your brain is more important than fashion.

By: KirTakat

KirTakat — Wed, 06 Dec 2006 10:10:07 -0800

You know, this actually strikes me as something I wouldn't mind wearing in the winter. There's been enough times I've been walking to my car and slipped on a piece of black ice and smacked my head into the ground that a little extra protection might have been nice...

I'm not sure I'd use it in place of a bicycle helmet, but it might be handy other times.

By: cadjez

cadjez — Wed, 06 Dec 2006 10:27:27 -0800

Ribcap was never intended to replace helmets. Comparing them against helmets is not necessary when this was not their goal in the first place. Ribcap's goal is to offer an option to those people that have already made the choice to wear a beanie instead of a helmet.

As for the thickness of material required to absorb impact. I don't believe there is a magic thickness. ikkyu2, when you say that 1"+ of foam is required to absorb typical impacts, you are refering to the medium density black bike helmet foams; specifically EPP or EPE. Just because EPP or EPE must be 1" thick to absorb impact does not mean that all foams must be that thick.

Benefits of Ribcap and d3o:

- Much more flexible than EPP or EPE. Would you want to wear a beanie that is rigid?

- Much, much more protective than a beanie. If you're going to wear a beanie during recreation anyway, why not wear one that protects you?

- Does not have to be as thick as conventional materials to offer the same protection. Drop tests against EVA showed that 10mm of d3o absorbs as much impact force as 16mm of EVA. Tests against a competitor's protective beanie (padded with PE) showed that the d3o padded Ribcaps absorbed over 4 times as much impact force.

- The US and Canadian National ski teams already made the choice in Turin to wear Spyder ski suits padded with very thin d3o in the elbows, fore-arms and shins rather than the bulky padding used before. d3o allowed them to be much more flexible and aerodynamic while maintaining enough protection to absorb impacts with gates at over 90kph!

In short d3o has undergone testing for the last 5 years and was not released without proof that it is extremely protective. Product development continues and possibly you'll see a thicker piece (if necessary) of d3o in a certified helmet or certified beanie someday. At this moment you have three choices for your head during winter activity: a beanie, an extremely protective beanie or a helmet.

By: MonkeySaltedNuts

MonkeySaltedNuts — Wed, 06 Dec 2006 12:24:22 -0800

Is it legal for Amazon to be selling Ribcaps in the USA (by shipping them in from a Canadien store)?

Is there a US rule that says to sell a "safety device" it must pass official tests? I think this is true for bicycle helmets. Is not passing tests the reason that Ribcap USA is not yet functioniong?

If so, is Amazon breaking the law?

By: footnote

footnote — Wed, 06 Dec 2006 15:44:41 -0800

Anyone else think it's weird that Cadjez joined...yesterday?

By: cadjez

cadjez — Wed, 06 Dec 2006 15:56:00 -0800

I am a rep for Ribcap and was searching the net to see what people were saying about it. Thought I'd add my two cents here. Hope that was ok.

By: footnote

footnote — Wed, 06 Dec 2006 16:04:02 -0800

Sorry, I was confused by the dates. I thought you had signed up immediately before the question was posted, which looked suspicious. Metafilter has a strict policy against deceptive self-linking, which you didn't really do, but you probably should have disclosed your affiliation up front.

By: cadjez

cadjez — Wed, 06 Dec 2006 17:11:15 -0800

No worries. Great to see so much discussion about our product, but no I did not start this thread.

By: hokie409

hokie409 — Wed, 06 Dec 2006 18:48:13 -0800

Seriously there was a rep on here and he could not offer any information on my original question? So I guess that there are no US distributors.

By: blag

blag — Wed, 06 Dec 2006 19:29:57 -0800

By bizarre coincidence, my father is meeting with d3o tomorrow. I'll give him a call in the morning and get him to ask them.

As an aside, I've played around with the stuff. It really is astonishing - fascinating properties.

By: MonkeySaltedNuts

MonkeySaltedNuts — Wed, 06 Dec 2006 19:33:20 -0800

#hokie409: Seriously there was a rep on here

And he didn't address #my question of whether Amazon was in violation of USA safety laws and that is what is keeping Ribcap out of the US market.

By: ikkyu2

ikkyu2 — Wed, 06 Dec 2006 19:53:50 -0800

ikkyu2, when you say that 1"+ of foam is required to absorb typical impacts

I didn't say that, Chuckles did.

I notice that you updated your Ribcap website to reflect some of the stuff you posted here in this thread.

By: Chuckles

Chuckles — Wed, 06 Dec 2006 21:31:06 -0800

I don't believe there is a magic thickness.

I don't believe there is a magic thickness either. I believe given a certain velocity at impact, and a certain maximum acceleration, there is a minimum distance. Any shorter, and the acceleration exceeds the safety limit.

Perhaps a more detailed analysis will demonstrate my point.. First off, based on braininjury.com, I will assume that the highest impact allowed is 50g. Now, lets take a look at what happens when you are riding along a street, collide with something, and slam your head into the ground.

Here is a collision profile graph I just drew, reduced to a single dimension for simplicity. The graph is of cyclist brain velocity vs. time (v_brain vs t):

Our cyclist is cruising along at 30km/h. At time (1) he notices that a collision is immenant.
He begins to break hard, for several seconds, but fails to stop. The collision occurs at point (2).
As the front wheel and fork crumple, and the cyclist's arms give way, there is a brief but severe deceleration. By point (3) the bike has stoped, but he hasn't.
Our ill-fated cyclist is flying through the air, but only for a second, because the ground is coming up fast - at point (4) the ground arrives.
Our cyclist's body hits the ground, his arm/shoulder/leg cussion the impact, which leads to a brief but gentle deceleration. Unfortunately, he just can't help it, his head hits the ground/wall/car door at point (5).
Finally, our cyclist's brain is going to stop, but how bad will it hurt? Point (6), ouch!

The helmet, if it is on, does it's job between point (5) and point (6).

The math which demonstrates a minimum thickness for helmet foam is actually very straight forward. First, given the maximum acceleration of 50g, and the speed at point (5) of 15km/h, how long is the minimum �t between (5) and (6)? Simple, velocity = acceleration x time, so:

v_{brain_0} = a_max x �t
15km/h = 50g x �t
4.17m/s = 490m/s² x �t
�t = 8.51 x 10^-3s

To be clear, this is the minimum �t. The actual event will be highly non-linear, but given a maximum acceleration, the quickest possible way to stop is to slow at a_max until you stop.

So we know that there is a minimum time of deceleration, 8.5ms, if the duration is any shorter, a_max would be violated. Time to calculate d_min, the distance our cyclist's brain travels while coming to a full and complete stop.

d_min = int_�t( v_brain(t) dt )
= int_�t( v_{brain_0} - a_maxt dt )
=int_�t( 15km/h - (50g x t) dt )
= 4.17m/s x �t - 490m/s² x �t²

d_min = 1.776 x 10^-2m

Which is, you know, pretty close to 1".

By: LordSludge

LordSludge — Thu, 07 Dec 2006 05:50:26 -0800

This makes intuitive sense, too. The rate of acceleration (deceleration, if it that makes more sense) is inversely proportional to the length that it has to slow down, i.e., thickness of padding.

(Dude, sweet formulas! How'd you do that, just lotsa HTML love? Or are you using some tool?)

By: Chuckles

Chuckles — Thu, 07 Dec 2006 18:06:26 -0800

I just did a lot of typing :P And I made a mistake.. I forgot the 1/2 when integrating a x t.. �t² is so small that it doesn't really effect the answer, d_min should be 1.774 x 10^-2m.

By: nicwolff

nicwolff — Sat, 09 Dec 2006 20:34:38 -0800

The point ikkyu2 and Chuckles are making is that d3o may protect well against point trauma by distributing the force over more of your body - for example, if you're whapping your forearms and shins into slalom gates - but it won't keep your brain from being tossed around in your skull. So maybe you won't get a lump on your head, but you might still get a concussion. I'm buying one cause I like sci-fi gear (I just ordered these goggles too!) and since I normally ride in a wool hat anyway.

By: ikkyu2

ikkyu2 — Tue, 02 Jan 2007 15:22:01 -0800

Well, I was actually pretty careful about not making a point, because I didn't want to get into an argument.

But the point I had in mind is that there have been decades of rigorous testing on protective headgear, largely carried out by militaries including the U.S. military. The findings have largely been that protective headgear doesn't protect, for reasons that were often wholly unanticipated when the headgear was designed.

For instance, during the 1960's a deformable polymer-ceramic composite was designed that was lightweight and could not be penetrated by 5.56 and 7.62 military rifle bullets. It was felt that this would be great to make a helmet out of.

Turns out that the impact of these supersonic bullets caused a deformation of the rigid inner shell of this helmet - brief, we're talking milliseconds - expanding inward to fill about half the volume of the helmet. The result was that skulls were crushed, even though no bullet penetrated.

Worse, because the helmet was quite thick, bullets that otherwise would have missed entirely, instead struck the helmet and, again, caused skulls to shatter. The thing was a net harm in combat.

There's some data showing that the head injuries that are prevented by bicycle helmets are actually more than made up for by the cervical spine injuries caused by the larger moment of the head+helmet combo rotating atop the neck; never mind the fact that bicycle helmets have holes and straps that can catch on things, which peoples' heads usually don't do. Traumatic brain injuries are no joke; but neither are C-spine injuries, which can result in complete paralysis below the neck.

My point is that theoretical ideas of how materials behave are not adequate when considering the design of helmets. They need to be tested to see how they perform in real-world situations.