MIPS?

[scott43]

Is there a difference between a pecker scientist and a wood pecker scientist?? boy we're going off the rails here...

 

[cantunamunch]

boy we're going off the rails here...

Are we?

Science | AAAS

www.science.org

 

[scott43]

Are we?

Science | AAAS

www.science.org

Lemme rephrase... *I'M* going off the rails here!!

 

[AlexisLD]

Thicker helmets cannot fully cope with the coup-contracoup injuries caused by the rapid deceleration occurring when the head hits a solid object and stops, while the brain keeps moving within the skull for a brief moment.....

A thicker helmet would reduce the deceleration occurring when the head hits a solid object, thus reducing the coup-contracoup... If you have twice the distance to absorb an impact, you can half the deceleration.

Another problem of most current helmets is that they are fully rigid up to the point of foam failure. This point is often above the force level that causes a concussion. I had a friend blackout from a concussion, forgetting a whole week of his life, without having a single mark on his helmet.

 

[AlexisLD]

Extending the energy absorption envelope to absorb lower impact energies means significantly increased frequency of replacement. From non-impact events. What's a practicable number, 3-4 helmets per season? 5?

Are you saying that you are hitting your head hard 3-4 times per season?

 

[AlexisLD]

1. After 150 km 600 grams becomes 6 kilos.
2. If I die on the road, there is about 99% chance it will be because a car or truck hit me and in that case even a full face motorcycle helmet is of no help.

Yeah, I don't road bike. For me it is skiing and mountain biking, so weight and car are a non-issue. I think we are seeing little improvement in helmets/norms because these markets are much smaller than road biking, which is driving the innovation away from head safety.

 

[Tom K.]

I don't get the laser-like focus on MIPS. But first:

OF COURSE MIPS CAN'T BE A BAD THING.

Now with regards to the whole rotational thing, I just went out into the garage, and none of the several old non-MIPS helmets I have that should have been thrown away by now have any problem rotating on my head, unless I crank every fit adjustment down to the point of migraine-inducing pain. And not being able to open my mouth enough to eat a Clif Blok.

It seems to me that the current testing standards that are sometimes described as kind of like having the helmet glued to your skull may not represent reality.

It seems to me that such a somewhat exclusionary focus on the rotational impact aspects of a helmet are not necessarily productive to advancing overall helmet safety. I find current things like dual-density shell materials used to reduce the g-force "spike" upon impact more compelling.

And venting. Cuz I hate hot helmets!

 

[cantunamunch]

Are you saying that you are hitting your head hard 3-4 times per season?

Catch up to your own content, will ya? One post prior you point out that

Another problem of most current helmets is that they are fully rigid up to the point of foam failure. This point is often above the force level that causes a concussion

I did absolutely say that halving the foam failure force and making the foam twice as thick would give you and me and everyone else in this thread a bunch of failed helmets. Yes. Like 5 or more per season.

From NON-skiing impacts. Like having gloves, wallet, goggles in the helmet and having the helmet drop off the lodge chair. Or from mishandling by baggage claim tossers.

From non-impact events.

 

[AlexisLD]

I did absolutely say that halving the foam failure force and making the foam twice as thick would give you and me and everyone else in this thread a bunch of failed helmets. Yes. Like 5 or more per season.

From NON-skiing impacts. Like having gloves, wallet, goggles in the helmet and having the helmet drop off the lodge chair. Or from mishandling by baggage claim tossers.

Missed the non-skiing impact. Yeah, good point. But... you need to match the energy of a head falling. Potential energy (mgh) is converted to the energy required to crush the foam (Fcrushing x crushing distance). Looking at mgh to get same impact energy with the full helmet falling from chair.

A head weights 5kg, so if you can fill your helmet with that much weight then you would have that problem. Black Diamond heaviest gloves are 350g. The iPhone 14 pro is 206g. 5kg is like 5x 1L bottles full of water. Do you carry gold when you ski? ;-)

The impact speed used during testing is 6.2 m/s, which corresponds to a free fall drop of 2m. Lodge chair should also be that height to cause a problem...

So if you have 1kg in your helmet that falls off 1m, you have 10x less energy than current standards. There is a decent gap to reduce foam crushing resistance.

That being said, even if easy crushing was a problem I would still be buying this product. But then, there are also other solutions so that crushing doesn't become a problem (e.g., working with foams that don't fail by crushing)!

And, even if the foam crushing resistance was not changed, a thicker foam would help at higher energy impacts, which is also a problem. A mountain biking fall can easily happen at a higher speed than 6.2 m/s (22 km/h). This is a ridiculously small number...

 

[cantunamunch]

. But... you need to match the energy of a head falling. Potential energy (mgh) is converted to the energy required to crush the foam (Fcrushing x crushing distance). Looking at mgh to get same impact energy with the full helmet falling from chair.

This is exactly where I disagree. You don't need to match the total energy of a head falling - if you're not filling the entire helmet.

The 5kg headform fallling over 2m is what, ~100 joules?

Let's say the helmet is a half sphere to keep things simple. Let's say it's a side impact - that crush energy is distributed over a 1/4 sphere of foam area.

A size L/XL helmet is what, approximately 10cm radius? 1/4 sphere area is therefore 314cm^2. 100 joules spread over 314cm^2, yes? A nice, convenient 1/pi crush ratio.


So, dropping that 200g weight from a 1m table gives us ~ 2 joules, yes? In order to exceed that 1/pi crush ratio from above, we just need an impact area less than 6.28cm^2.

Let's hope then, that that Iphone...or bike multitool say...doesn't engage the helmet corner-first. Or let's hope the phone isn't sitting on a set of car keys. And that's with current crush foams.

In the hypothetical scenario of a twice-thick foam with half the crush resistance that we were discussing above, 2 joules requires 12.5cm^2. We don't need a corner-biased fall anymore. Either of the top or bottom edges will do it - or a tilted fall onto a side edge of the phone.

Therefore, with the softer foam a much higher number of incidental events will generate point failures in the helmet foam. Therefore need to replace. Often. Which was my point. And also the design objective of the recyclable, almost-disposable cardboard helmet idea (from 2012!) I linked to above.

That being said, even if easy crushing was a problem I would still be buying this product. But then, there are also other solutions so that crushing doesn't become a problem (e.g., working with foams that don't fail by crushing)!

And, even if the foam crushing resistance was not changed, a thicker foam would help at higher energy impacts, which is also a problem. A mountain biking fall can easily happen at a higher speed than 6.2 m/s (22 km/h). This is a ridiculously small number...

This part I agree with. But you're not going to get more than a few skiers to wear snowmobile+ rated helmets ...because fashion must

 

[crosscountry]

ut you're not going to get more than a few skiers to wear snowmobile+ rated helmets ...because fashion must

Not sure I get what you're saying...

Fashion can go every which way. It's not that long ago wearing helmet is unfashionable. But now, helmet IS the fashion!

 

[cantunamunch]

Not sure I get what you're saying...

Fashion can go every which way. It's not that long ago wearing helmet is unfashionable. But now, helmet IS the fashion!

Go find a snowmobile helmet that fits your head. Then put it next to your ski helmet.

The difference between the two is 100% due to fashion, looks and convenience.

Thereby proving that fashion, looks and convenience trump safety. Unless ski impacts are all at less than 13mph, as discussed above?

 

[crosscountry]

But fashion is created by the manufacturers (or their marketing department)!

 

[cantunamunch]

But fashion is created by the manufacturers (or their marketing department)!

Within an envelope of consumer expectations ... and consumers expect to not look like extras on Space Balls.

But, you are mostly right...and the proof is that some helmet manufacturers are trying to push the consumer expectation envelope towards bigger + better. As INEOS were mentioned above,

Big helmets, weird visors and an unzipped gilet at the Tour’s opening TT

New aero trickery from the marginal gains specialists

www.bikeradar.com

 

[AlexisLD]

This is exactly where I disagree. You don't need to match the total energy of a head falling - if you're not filling the entire helmet.

The 5kg headform fallling over 2m is what, ~100 joules?

Let's say the helmet is a half sphere to keep things simple. Let's say it's a side impact - that crush energy is distributed over a 1/4 sphere of foam area.

A size L/XL helmet is what, approximately 10cm radius? 1/4 sphere area is therefore 314cm^2. 100 joules spread over 314cm^2, yes? A nice, convenient 1/pi crush ratio.


So, dropping that 200g weight from a 1m table gives us ~ 2 joules, yes? In order to exceed that 1/pi crush ratio from above, we just need an impact area less than 6.28cm^2.

Let's hope then, that that Iphone...or bike multitool say...doesn't engage the helmet corner-first. Or let's hope the phone isn't sitting on a set of car keys. And that's with current crush foams.

In the hypothetical scenario of a twice-thick foam with half the crush resistance that we were discussing above, 2 joules requires 12.5cm^2. We don't need a corner-biased fall anymore. Either of the top or bottom edges will do it - or a tilted fall onto a side edge of the phone.

Therefore, with the softer foam a much higher number of incidental events will generate point failures in the helmet foam. Therefore need to replace. Often. Which was my point. And also the design objective of the recyclable, almost-disposable cardboard helmet idea (from 2012!) I linked to above.

I see what you mean. Well, first, I think that 1/4 of a sphere is way too big of a common surface between the head and the helmet (e.g., a helmet is often just 1/2 sphere... if you get an impact on the back of your head then at most 1/4 of the sphere is involved, but there is little chance that the sides/top of that 1/4 of a sphere will do anything in compression). But more importantly, I am not sure that your modelling is correct (or that is a situation that will happen often, but that is another discussion). If you have a phone/helmet that fall together, when the helmet touches the ground the phone will touch the helmet with its corner, then the force between the helmet and the corner of the phone will change the linear and angular momentum of the phone, assuming the corner of the phone and its center of mass are not on a line that is perfectly aligned with gravity. This means that the phone will start rotating. This will reduce the effective mass of the phone at the impact and the exact level depends on the angle of the phone, its inertia properties, the distance between the CM and the corner, etc. This will also create multiple small impact between the phone and different point of the helmet, not all of which being in contact with the ground, dissipating the energy in a distributed way. Imagine a screwdriver oriented vertically vs horizontally being dropped onto your foot. I know which orientation I prefer! If you want to try it, go with chopsticks!

So in real life, I would think that you would get much less of a problem than what you are thinking. Regardless, (1) I am sure I can avoid the situation you describe, and (2) replacing my helmet more regularly would not bother me excessively if I can avoid a concussion. I think many people would choose safety if they know it would offer them additional protection (think avy beacons, airbags, spot beacons, etc). Damn, I bought a MIPS helmet, not really believing that it works in real life, just "in case" it might work. I am ready to ditch that as soon as someone proves that it is not working (the proof is already kind of there) and propose a better solution!

 

[François Pugh]

Thicker helmets? Heavier? Are we still talking about road cycling? Don’t get me wrong, I am all for more safety but if that means I’d have to wear a 1 kilo helmet, I will take my chances with something much lighter albeit less safe.

OOOO, a helmet thread!
Can I play too?

I don't have a kitchen scale handy and unfortunately my full-face motorcycle helmet is too old to be on the list here, https://www.webbikeworld.com/motorcycle-helmet-weights/
But I'm pretty sure it's over 1.5 kg, judging from the other helmets listed. You would think it would feel heavy, but after I start riding, I don't even realize I have it on. I'm sure it would be the same for a heavier ski helmet. The problem with motorcycle helmets for skiing, other than not being in fashion is having the face shield fog up.

 

[Tom K.]

@AlexisLD: paragraphs, man, paragraphs!

Even if they are somewhat random, as I know mine are.

I gotta say, it does my aging engineer's brain good to follow your and @cantunamunch technical jousting. Keep it coming!

 

[Zirbl]

Or from mishandling by baggage claim tossers.

You care about helmets enough to be one of the main posters in this thread, but put them in checked baggage?

 

[cantunamunch]

You care about helmets enough to be one of the main posters in this thread, but put them in checked baggage?

Certainly. And the proof is I already max out the hand carry allowance with my boots.

 

[crosscountry]

Certainly. And the proof is I already max out the hand carry allowance with my boots.

"Max out"?

Oh, you mean you put your boots inside the carry-on instead of wearing them?