[jonKranked]

Actually, E = .5mv^2 is the relevant equation in determining the impact force and subsequent g-loads associated with an impact, and relates to momentum as E = p^2/2m. Momentum (p) is a vector quantity while E is a scalar. Energy is basically the rate of change of momentum. Biggest issue being that the force of impact increases at the square of velocity, not at a 1:1 rate like the momentum equation might suggest.

Well yes, but i was trying to keep is simple for the RM general population. For now

I would argue that the way you crash has MUCH more influence than the speed of travel in most cases, but obviously in some crashes traveling faster does mean you will hit harder. This means that the decision of what helmet you choose has MUCH more to do with how you crash than what type of vehicle you are traveling on.

Agree 100%.

Since you can't choose how you will crash, then the entire premise of the PB article is flawed. IMO this article is total bullsh!t and oversimplified to the point it makes no sense. Every single piece of anecdotal (real world) evidence from people who ride both mx and dh, and people who have used both types of helmets point to the mx helmet preventing concussions moreso than a dh helmet.

I wouldn't say its entirely flawed; the variability of impact (crash) method is an assumption when dealing with these types of tests.

The one good thing I'd argue that the article has done is gotten people to have a more in depth though process regarding the helmet styles they are using(dh v moto), and challenges the notion that "moar is bettar"

I would also argue that the quality of the helmet matters quite a bit too, and it is possible that some mx helmets offer better protection than many dh helmets regardless of impact speeds. So this is another factor that is not dealt with in the article.

possible, yes, but unlikely. when you look at a transmissibility curve for a give piece of foam, it's going to give you good protection over a range of impacts forces; ie there's a min and max. When you increase the density of the foam, that range not only shifts upward, but tends to slightly decrease as well. So you're cutting off protection at the low end of the impact force spectrum in order to increase protection at higher impact levels. Moto helmets commonly utilize denser EPS than dh helmets.

 

[davec113]

possible, yes, but unlikely. when you look at a transmissibility curve for a give piece of foam, it's going to give you good protection over a range of impacts forces; ie there's a min and max. When you increase the density of the foam, that range not only shifts upward, but tends to slightly decrease as well. So you're cutting off protection at the low end of the impact force spectrum in order to increase protection at higher impact levels. Moto helmets commonly utilize denser EPS than dh helmets.

I think some moto helmets may be superior to any dh helmet because of the use of multi-density EPA liners which attempt to address the different needs of lesser vs greater impact speeds. This construction is not even mentioned in the PB article, and AFAIK is fairly common and not limited to $500+ helmets like the Shoei VFX-W.

I can definitely say I'd rather hit my head at any speed wearing my Shoei vs my TLD D2.

 

[jonKranked]

I think some moto helmets may be superior to any dh helmet because of the use of multi-density EPA liners which attempt to address the different needs of lesser vs greater impact speeds. This construction is not even mentioned in the PB article, and AFAIK is fairly common and not limited to $500+ helmets like the Shoei VFX-W.

I can definitely say I'd rather hit my head at any speed wearing my Shoei vs my TLD D2.

multi density / dual layer foams are starting to become common in MTB helmets as well, and i think it should be used in all helmets; helps greatly increase the range at which you get good protection.

Also, I'm assuming you mean EPS, not EPA. Regardless, I wish more companies would switch to using EPP.

 

[ChrisKring]

HIC = Integral ((a^2.5)*dt)

That's the Head injury criteria. Go read about the Wayne State testing.


Since distance is defined by the design, acceleration needs to be optimized to decellerate the head using the entire distance in order to minimize the accelleration. That's where the foam stiffness comes into play.

no mater how you look at it, more distance (thickness) is better.

Anyway, this thread is full of misinformation. Go read how helmets are tested. Not even close to 60 mph

 

[-BB-]

We need more helmets like this if we want ultimate protection:

 

[jonKranked]

Helmets are tested at over 9000 miles per hour.

 

[IH8Rice]

We need more helmets like this if we want ultimate protection:

"I knew it. I'm surrounded by as*holes!"