kurt M

SCUBA shops also sell a small plastic web and line cutter than is cheap and sticks where you want with velcro. They are in the $3 range. They are a razor blade molded into a plastic hook like handle and slice web like butter.


My computer will not load the videos. Has anyone else had a problem or is it on my end?

sleder

Greg, I watched the videos a few times. What I saw was the neck was enlongated in BOTH H&N devices however NOT to the same degree. What I saw with the Hans not only did the belt separate from the device, but the duration and the length of the neck being pulled substantially longer. The conclusion I am coming to is Isaac Device, however the remaining question is how does the Isaac compare to the R3.
Am I interpeting this correctly?

gbaker

These video files are large. They have been slightly compressed but not optimized for the net. In raw form they typically are over 100MB, so what we have here is not bad. We hope to trim them down to ~ 10MB.

If you are on ADSL you should be able to download the large HANS file in a few minutes. It will play in MS Media player.

gbaker

Yes, you are; that's a good summary.

I can't comment on the R3 because they haven't released their test data, although they admit the loads are higher.

We normally don't like videos, because they can be easily misinterpreted, but these correlate very well with load data--especially lateral load data and head Gs. If you are using an advanced viewer from the likes of SAI, notice the head position at ~130ms post impact. This corresonds to ~10secs on the MS Media Player. The difference in lateral head torque is huge.

racergreg

Thanks for this great info, Gregg! Well, this certainly shows what Redline is always talking about with respect to shape change!

Gregg: It appears to me that the shoulder belts are not very tight. Is this an illusion or are we seeing belt stretch in action? Also, they seem to be anchored above the dummy's shoulders, not level or slightly below as is recommended.

DJF1

WOW...thanks for the video's! Very revealing which makes me hate the 900 pound gorilla even more... Its pretty amazing to see the hans getting off the belts...

gbaker

That's the first thing everyone says, including yours truly the first time I saw one of these. The belts are very tight, probably tighter than you could get them if you were the driver. You are seeing a combination of shape change and belt stretch.

They are anchored correctly.

Don't forget that a 180# driver hit with 68Gs will load the belts to 12,240#. Six tons is going to bend everything out of shape.

DAR951

Greg,

This is a terrific step towards what I assume will be an SFI 38.1 certification package. My one remaining question is what/how are you planning to satisfy the "no additional motion, other than seat-belt release" requirement.

With the season only a couple months away, I'm way over the line towards an Isaac, but would love to know if I'll still be able to use it when the inevitable requirement for an SFI 38.1 certified device comes into play.

Thanks very much for sharing your time, data, and insight.

ltc

Best resson I can think of to go on that 'after the holidays' diet

mitch236

Actually I'm not sure what these videos show. They do show the need for full containment seats as part of the whole package. True, the belts slip off the HANS during the video but would that occur in a race seat (full containment)? The other info I would like is the data. What is the load on the head and neck in each scenario? The videos are nice but it is hard to tell what the actual load is. You can see that even though the belt slipped off the HANS, it seems that it is still working to some degree.

Also, being used to critiquing studies, who paid for these studies?

I'm not trying to start a war here, just playing devil's advocate. We all want the facts. I will be the first to trade in my HANS if Isaacs if proven to be safer.

kurt M

The problem was on my end, got them to load. I bet you were not unhappy with the results!

Do you have a non binding guess as to why the R3 loads are higher? Take up time?

What load #s did you see?

fatbillybob

I have questions too. perhaps the first pulse is the one that kills you and if the hans stays on for that who cares if is pops off later? I personally would like it to stay on but...all the device has to do is work. I don't care it it worked then broke in half . However, full containment seats may not be the obvious choice. On paper fine but we get surprised by crash tests that's why we have them partly. Until the devices are tested with full containment I don't think you can draw 100% conclusion eventhough I personally use one. And even with full containment hans can slip off. I changed to a four shoulder system and full containment seat and I am worse off than with my omp carbon seat and 5 point sabelt. With my old system the hans never slipped while driving. I never crash tested it. With my new system I can't keep these damn hans belts in place at all and I am still trying set-ups to get them right. I get belt dumping off the hans yokes and hans says it's o.k. because the belts are still holding on the collar lips. I don't buy it and I am still trying to work with the scroth rep to get these belts to stay on all the time. No luck yet however. And finally as to hans slipping wasn't there a quote long ago from Dr. Melvin something like "the dummy is not a human so the chest deforms differently" as a way to explain some slipping? Now I think that is a total cop out! All this HN stuff makes my head hurt.

M758

Well looking at both videos all I can see is he HANS slips off the belts where the ISAAC does not. Does seem like the ISAAC has more displacment, but as Gregg has said displacement is not at issue. It is the force that is the issue. This cannot be determined from the video (at least by me).

So it does show that the belts can come off, but franky neither dummy seems to be having a good time. Gregg I am sure you have head load numbers for this test for the ISAAC. Do you know the HANS test numbers with ony belt off?

kurt M

FBB If you watch the vid in slow you can see that the HANS did not stay on during any meaningful portion of the pulse and if any energy was absorbed it was due to the side that did not slip off. This caused the head to swing hard to one side and I bet that opens a box full of issues as well. It looks from the vid as if the belt stayed in place and the body moves from under it. In a full containment you will still move very far forward and likely out of the containment portion of the seat. S side net would keep you head from going into the passanger seat but you body is moving a long way and out of place. This is but conjecture on my part. Not everyone has a full containment system. In fact most DE and Club racers do not. Would this mean that you have to mandate that Hans only in full containment and ISAAC or R3 in all other race seats or systems?

The ISAAC vid seems to show a lot of head movement before take up of the rollers and dampers. It also finally arrests the head with it pointing crown forward. Do the other systems do the same and what does this mean as far as brain movement in the skull?

This was one sore dummy ether case. I’ll take sore over dead or can’t feel a thing anyday.

As always it is still a complex set of questions and problems....

RedlineMan

Complex, indeed!

There are two things that are constants, I believe.

1) The head will rotate forward with the chin turning down into the chest.
2) Surviveable longitudinal neck extension is higher than lateral.

1) From my reading, it has been found that the brain (and the body in general) will stand VERY high loads as long as that load is relatively linear. Any deviation from this type of load (read-any kind of whip) reduces that capacity greatly. Further, the forehead is the strongest portion of the skull. The natural rotation of the helmeted head forward and down puts restrained loads on this strongest portion of the skull. This first phenomenon is a good thing for the brain itself, in other words. The neck is another matter.

2) The neck has far more elasticity in a longitudinal direction that latterally. Witness the placement of the Hangman's Noose. It was found that placing the knot in front of or behind the head only killed the wearer through asphyxiation. Placing the knot on either side of the head achieved the desired result; immediate death through severe Basilar Skull Dislocation.

Regarding the tests posted here, my impression is that the Isaac controlled lateral motion far better. It also appeared as though the HANS still did something. This is all guesswork, and quite why viewing video is not indicative of anything concrete.

- I'd like to see the neck tension loads plotted -vs- time.
- Is there a numerical constant used to insure equal harness tension, pre crash?
- I would assume HANS was not privy to this test.