RedlineMan

Ha;

That is a point I was going to make regarding stretch. IF you prescribe to the notion that having a healthy amount of stretch that allows a gradual dissipation of energy is a good thing, how do you then control the body properly if there is another impact? You will certainly have more motion than you want with the old model of 15-17% elongation. More than likely, the occupant will escape the belts. The other problem is that it does NOT reduce stress, it INCREASES it.

The thing that makes this low stretch model work - again - is that it has been found that most of the human body can take a huge amount of stress, if that stress is rendered in a more immediate time frame. Broken shoulders and ribs are far preferable to concussive head and torso injuries. Blunt force trauma, I think they call it. Not good.

To some extent, we are dealing with extremes here, but in the extreme this stuff makes a difference. It is pretty well proven science.

RickBetterley

Another point - I expect that it is critical that the HANS device be held firmly by the shoulder belts. That would (should?) mean that stretching belts could interfere with the proper functioning of the HANS device.
I hope to never find out first hand.

gbaker

Stretch = bad.

fatbillybob

I think secondary impact and belt stretch is where the sidenets really come into play....And I hate to say it but the full containment seat is nice... but I think you still need sidenets. I think some rules are starting to mandate either sidenets OR FC seats but I am not sure they are really doing any good safetywise by exempting some drivers from sidenets.

kurt M

From what I have read and understand a high but short duration G pulse is better than a complex messy slightly lower total G event. Stretch does not mean a softer deceleration but the inverse, a longer acceleration of the body before deceleration. The time and distance that your body is moving as it comes out of the seat is energy adding up and must be paid back when the belts go tight. A car impact is not like a bungee jump. The car is moving and crushing. Let it do the work.

gbaker

^ yup

In a crash, the seat stops and your body keeps going. The net effect is that your body accelerates away from the seat. Eventually the belts catch it. The sooner they catch it, the slower the catch velocity and lower the pain.

X2 for your head relative to your body. The 68G sled at Delphi will generate ~105 head Gs.

This is counterintuitive. It took me a long time to get my head around it. The light either comes on or it doesn't.

Analogy: A catcher catches a baseball, which is strapped to a rocket. Does the catcher want to be close to the pitcher, or far away?

RedlineMan

^^^^Doubletriplequadruple Yup!!!!

Repeat, repeat, repeat, and it will eventually sink in. The old paradigm is dieing far too slowly. Look at the evidence that slow = dead and you can't escape it.

I offered it before, but it didn't click. What is the safest cockpit in the world? Is it not ironic that it also offers the most potential for devastation? The F1/IRL/CHAMP cockpit is the most surviveable in the world, all while offering the most energy to overcome. How? It is restrictive by default. There is virtually no room for movement except forward, and H&N devices have largely solved that problem.

Next best are our good old boys in NASCAR. If they hit/get hit on the right, they are good. Left side is far less so, but even they sometimes have right side nets mounted on the left as well, which is a GREAT idea. The most safety consciuos (Kyle Petty, for one) use PPI carbon cockpits that are a virtual open wheel cockpit inside their tank.