Helmet rigidly attached to armor?

[Kelvrick]

My wife works trauma rounds in the only trama center in the area. Spinal injuries are by percentage a relatively small percent of motorcycle injuries. The overwhelming majority of injuries are pelvis and leg crushes. When head injuries happen it's usually a matter of time before the Gift of Life crew come in, so they can't be ignored. But by the numbers it's not the most common thing they need to treat.

I think you'd be introducing a whole different problem of physics if you start adding rigidity there and not everywhere else. That energy has to get displaced somewhere. If not the head then other parts of the body.

Large metal tank in front of groin in a vehicle that accelerates quickly and often decelerates very quickly? Who could have imagined pelvic injuries.

With a helmet that big, I can't imagine the wind drag. I've never ridden cruisers though, only sportbikes and even with current helmets, you can definitely feel the wind when you go above the windscreen.

Ditto on the helmet size. I wear a small scorpion and a lot of my friends often say my helmets are too small. I just wish them luck on their helmets that can twist off.

I know Dainese has some of those new "air bag" suits now that inflat when you cash.

 

[Kroze]

same reason I love skydiving.

It's funny to see people wearing armor skydiving. I think you have a bigger problem when the chute fail than whether you're wearing your helmet or not.

 

[Squisher]

So, what we need is a normal helmet that can pivot inside another helmet that is attached to a breastplate.

 

[KentState]

It's funny to see people wearing armor skydiving. I think you have a bigger problem when the chute fail than whether you're wearing your helmet or not.

I hope this is sarcasm. There are many things to bump your head on when sky diving even if you have a working parachute.

 

[Imp]

Isn't that the Star Trek Voyager and First Contact space/environmental suit?

 

[Throckmorton]

When the helmet fits tightly then the load from the impact is spread out more evenly across the skull. In a loose helmet only a small part of the foam (the hard foam that protects you, not the soft foam that's there for comfort) is in contact with your head, which is more likely to damage the user.

Is spreading the impact really that important? If you slam your head into the foam, is it going to crush your skull? Because other than that, the big danger is decelerating your skull, while your brain keeps moving and slams into the bone, which the spacesuit helmet would protect from just as well.

 

[JCH13]

Is spreading the impact really that important? If you slam your head into the foam, is it going to crush your skull? Because other than that, the big danger is decelerating your skull, while your brain keeps moving and slams into the bone, which the spacesuit helmet would protect from just as well.

It's the same reason that seat-belts are starting to have retractors: any amount of extra space is bad. Even if the extra pressure from an ill-fitting helmet is not too damaging picture this:

The loose helmet hits foreign object, decelerates, stops (relative to the users head), next, the users head slams into a stationary helmet and decelerates.

Contrast that with a tight-fitting helmet where the head is being decelerated by an object that is also decelerating (but still moving away from) the users head.

In the second case the users head gets slowed down and stopped over a longer distance, leading to the brain experiencing lower accelerations, all else being equal. Make sense?

 

[Throckmorton]

It's the same reason that seat-belts are starting to have retractors: any amount of extra space is bad. Even if the extra pressure from an ill-fitting helmet is not too damaging picture this:

The loose helmet hits foreign object, decelerates, stops (relative to the users head), next, the users head slams into a stationary helmet and decelerates.

Contrast that with a tight-fitting helmet where the head is being decelerated by an object that is also decelerating (but still moving away from) the users head.

In the second case the users head gets slowed down and stopped over a longer distance, leading to the brain experiencing lower accelerations, all else being equal. Make sense?

No, it doesn't make sense. What is this object? If it's a stationary object, then the snugger the helmet the faster your head decelerates. If your head hits the inside of the rigid helmet, it might hurt the skin layer more, but your head would compress the foam more and decelerate over a longer distance.

 

[JulesMaximus]

Is spreading the impact really that important? If you slam your head into the foam, is it going to crush your skull? Because other than that, the big danger is decelerating your skull, while your brain keeps moving and slams into the bone, which the spacesuit helmet would protect from just as well.

Unfortunately, the space suit helmet doesn't allow you to turn your head like a motorcycle helmet does to look around you, up or down, or behind you which you kind of need to be able to do while riding a motorcycle.

 

[Howard]

No, it doesn't make sense. What is this object? If it's a stationary object, then the snugger the helmet the faster your head decelerates. If your head hits the inside of the rigid helmet, it might hurt the skin layer more, but your head would compress the foam more and decelerate over a longer distance.

Don't forget that with a loose-fitting helmet, you don't get an appropriate load distribution on your head - it would be much more localized. You want to lower stress (mechanical stress), not increase it.

I'm tempted to say that your head would only be decelerating over a longer distance because it would be starting out at a comparatively higher velocity - isn't that the only way it would go through more foam? But I don't completely understand the physics of it, so I won't stand by that.

EDIT: I see my first point has already been discussed.

EDIT2: Let's look at it this way: you can wear a helmet can provide 1" of EPS all around the skull, and you have a rigid wall covered with 1" of EPS. If you slam your head into a bare rigid wall with the helmet, are the a) acceleration of your brain, and b) stresses experienced by your skull higher or lower than if you were to hit your head against the EPS-covered wall at the same velocity?

 

[JCH13]

No, it doesn't make sense. What is this object? If it's a stationary object, then the snugger the helmet the faster your head decelerates. If your head hits the inside of the rigid helmet, it might hurt the skin layer more, but your head would compress the foam more and decelerate over a longer distance.

When your head hits the inside of the helmet there's an acceleration spike that can damage the brain. If your head moves with the helmet, and is in contact with the inside surface when the outside surface strikes, there isn't such a large acceleration spike (severe impact event).

I've done some helmet R&D and also designed crash structures for a race car. This is something I'm familiar with on a professional level.

 

[Throckmorton]

Don't forget that with a loose-fitting helmet, you don't get an appropriate load distribution on your head - it would be much more localized. You want to lower stress (mechanical stress), not increase it.

I'm tempted to say that your head would only be decelerating over a longer distance because it would be starting out at a comparatively higher velocity - isn't that the only way it would go through more foam? But I don't completely understand the physics of it, so I won't stand by that.

EDIT: I see my first point has already been discussed.

EDIT2: Let's look at it this way: you can wear a helmet can provide 1" of EPS all around the skull, and you have a rigid wall covered with 1" of EPS. If you slam your head into a bare rigid wall with the helmet, are the a) acceleration of your brain, and b) stresses experienced by your skull higher or lower than if you were to hit your head against the EPS-covered wall at the same velocity?

Hitting the EPS wall with your bare skull will put less force on your brain until the EPS fully compresses and resistance goes way up, because a smaller area of your skull is compressing the EPS.

The inside of the helmet is distributing load across a big section of your skull, so of course it won't compress as easily and will put more force on your brain at the beginning of the impact.

Correct me if I'm wrong, but what matters in a motorcyle accident is the force of your brain hitting your cranium, not the force per unit area of skull.

That's the problem with current bicycle helmet designs at least- they focus on armoring your skull, but the hard foam doesn't cushion your brain.

 

[JulesMaximus]

Hitting the EPS wall with your bare skull will put less force on your brain until the EPS fully compresses and resistance goes way up, because a smaller area of your skull is compressing the EPS.

The inside of the helmet is distributing load across a big section of your skull, so of course it won't compress as easily and will put more force on your brain at the beginning of the impact.

Correct me if I'm wrong, but what matters in a motorcyle accident is the force of your brain hitting your cranium, not the force per unit area of skull.

That's the problem with current bicycle helmet designs at least- they focus on armoring your skull, but the hard foam doesn't cushion your brain.

Still, any helmet is better than no helmet.

 

[Throckmorton]

Still, any helmet is better than no helmet.

But the wall covered in EPS is the equivalent of my rigid helmet armor.

More force applied to the skull because it doesn't conform to your head shape, but less or the same force applied to your brain depending on how hard the foam is.

 

[Throckmorton]

When your head hits the inside of the helmet there's an acceleration spike that can damage the brain. If your head moves with the helmet, and is in contact with the inside surface when the outside surface strikes, there isn't such a large acceleration spike (severe impact event).

I've done some helmet R&D and also designed crash structures for a race car. This is something I'm familiar with on a professional level.

Why is there more of an acceleration spike if your head hits the inside of a loose helmet? Why not the same acceleration spike when a head inside a tight helmet hits a hard surface like a car?

 

[JCH13]

Why is there more of an acceleration spike if your head hits the inside of a loose helmet? Why not the same acceleration spike when a head inside a tight helmet hits a hard surface like a car?

First thing to note, and it's secondary to your question, but a car is generally softer than other things your head may hit (like pavement) car body panels will often dent in further than the helmet would, 2-4" or so.

There are two impacts to really look at: one is the helmet -> foreign object, the second is head -> inside of helmet.

If your head is snug inside the helmet, i.e. it moves very little before contacting the hard foam (which is critical for protection), then when the helmet slows down as it contacts the foreign object your head will hit the hard foam when it and your head are moving at close to the same speed.

If your head is loose inside the helmet, the helmet will slow down more (or even stop) before your head hits it. This larger speed difference when your head hits the inside of the helmet is what makes that initial impact have a larger acceleration pulse.

 

[Throckmorton]

First thing to note, and it's secondary to your question, but a car is generally softer than other things your head may hit (like pavement) car body panels will often dent in further than the helmet would, 2-4" or so.

There are two impacts to really look at: one is the helmet -> foreign object, the second is head -> inside of helmet.

If your head is snug inside the helmet, i.e. it moves very little before contacting the hard foam (which is critical for protection), then when the helmet slows down as it contacts the foreign object your head will hit the hard foam when it and your head are moving at close to the same speed.

If your head is loose inside the helmet, the helmet will slow down more (or even stop) before your head hits it. This larger speed difference when your head hits the inside of the helmet is what makes that initial impact have a larger acceleration pulse.

I don't get it. Your description makes it sound like the helmet decelerates gradually when it hits a rigid object, which it doesn't. It stops immediately, and the only cushion is the amount that the foam compresses.

 

[JCH13]

I don't get it. Your description makes it sound like the helmet decelerates gradually when it hits a rigid object, which it doesn't. It stops immediately, and the only cushion is the amount that the foam compresses.

Well, the helmet doesn't stop immediately, I promise. The outside of the helmet deforms almost as easily as the inside does, it is only protected by a thin layer of plastic or reinforced plastic.

 

[Throckmorton]

Well, the helmet doesn't stop immediately, I promise. The outside of the helmet deforms almost as easily as the inside does, it is only protected by a thin layer of plastic or reinforced plastic.

So are you saying my spacesuit helmet would deform and slow down over a period of time, then stop deforming, THEN your head would hit the foam and get less cushioning because the outside has already done its deforming?

 

[JulesMaximus]

But the wall covered in EPS is the equivalent of my rigid helmet armor.

More force applied to the skull because it doesn't conform to your head shape, but less or the same force applied to your brain depending on how hard the foam is.

No, it isn't.

 

[JCH13]

So are you saying my spacesuit helmet would deform and slow down over a period of time, then stop deforming, THEN your head would hit the foam and get less cushioning because the outside has already done its deforming?

More or less.

 

[wetomb]

I wear a neck brace when racing downhill mountain bikes. It stops over extension and compression of the neck pretty well and doesn't restrict movement that much. Probably would be useless for looking sideways at an intersection though. I've got a mountain bike specific model but there are motocross models as well. http://www.leatt-brace.com/