Greg Fishman

I see no cause for concern here, but I am not an engineer. The piece did its job and it was a substantial impact. Am I wrong here?

Bryan Watts

Based on the names of the images that Greg posted, I'm assuming those numbers and pictures from a test at the Delphi lab as opposed to actual numbers and pictures from the Nextel Cup crash.

chrisp

Anyone know when the cheaper HANS is coming out?

PPo

<warning - pure speculation>

From what I understand about Carbon Fiber is that it is difficult to design such that it is strong on all planes of force. Perhpas the HANS is very strong when getting pulled straight forward by it's teathers, but not very strong when the teather pulls the HANS with a twisting motion (side impact).

After seeing the crash on TV and I am not completly convinced that the HANS was designed for that type of crash... I am not saying it didn't help, but for a mutiple roll crash with forces coming from many different directions, there may be better H&N designs suited to this type of crash...

I dunno..
P

hacker-pschorr

I agree unless this is common to hold onto your hemlet during a crash, it's really the only place to grab.
I hope I'm never in a situation to make that decision.

I've seen open wheen drivers say they cross their arms, grab the harness during a crash. Anything to keep their hands in the cockpit and away from the wheel.

I wonder if his hands pulling down on the helmet caused excess strain on the HANS? Just tossing this out there.

Bryan Watts

I can imagine that would add any appreciable strain...we're probably talking 70+ G's already.

ltc

No, I think that wouldn't sit well with the wife to redesign the basement.

I was the kid in grade school who was shown a glass and asked if the glass was half full or half empty and responded that it's just twice as big as it needs to be.

It's interesting trying H&N devices for comfort/use, understanding their design philosophy....but I think I'll (hopefully) leave testing for the REAL crash dummies.

kurt M

G baker thanks for the pix of the failure.
I might guess that the shots are after a sled test. Are they? Those are big G #s for sure! If so was the device compromised in function during the test by the failure? It did crack but was it able to do the job during as it sounds like was the case in the real world "testing" Granted they are race car drivers and not structural failure analysis experts.

“Then came word Friday that Casey Mears' device also cracked when he hit the wall hard on Sunday. Initially unaware of that crack, NASCAR has since taken possession of the HANS and also is sending it back.
Mears said the crack in his HANS was in the centre and appeared as if the left strap had been tugged too hard. “
''In a hit like that it probably should have (cracked),'' he said. ''It didn't crack hard enough where it wouldn't have done its job. It just cracked enough where you wouldn't feel good about using it again.''

gbaker

Yes. As someone noted, that's the SFI test.

The head loads were higher than they would have been had the device remained in one piece--the additional strain would dictate as much. One would have to compare the results to those from a test during which the fractures did not occur to be able to put a number on it, but I suspect the increase is small.

This device "passed" the SFI test, though lateral load measures were high.

The fracture at the lower (yoke?) area was caused by a combination of compression and horizontal sheer, and can be fixed rather simply--though at some expense. Of greater concern is the upper fracture because it exposes CF shards near the carotid artery.

In a head-on impact the loads are distributed evenly over both sides, but asymmetrical loading in offset impacts will be substantial. That's probably the culprit.

A 3,000# design criteria sounds small for a high performance device. That's just north of a theoretical 100Gs. We're using 6,000# for the damper version (~3,000 for the Link model) and considering 8,000 for a potential revision--though the revision is not for strength reasons.

All safety components should be considered sacrificial. Whatever energy it takes to crack, twist, bend, stretch, fracture or break something is energy that probably would have otherwise ended up in your body.

chrisp

http://www.nascar.com/2007/news/head...low/index.html

Here's some follow up info from NASCAR if you haven't seen it already.

gbaker

A safety product having a safety factor < 1.0.

M758

Ding, ding, ding we have a winner.

gbaker

The next time I drive across a bridge and the steel bends, or the concrete cracks, I'm going to say, "Wow, what a great bridge! It was designed to break at a certain load!"

cooleyjb

So the bridges you drive on don't bend, expand, etc. and the concrete in Florida doesn't have any cracks.

This is the kind of passive agressive statement I was talking about that annoys many poeple and makes people have a general dislike of Isaac. You lose credibility with some people when you act like this.

Greg Fishman

Ridiculous analogy.