H&N restraints - need opinions
#136
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Originally Posted by chrisp
Speak to a samll sailboat/catamaran dealer that actively sells trapeze harnesses. Some companies, like Magic Marine, include a saftey knife with each harness. It's a classic webbing cutter that won't cut you but easily cuts webbing. They also sells these knives separately. they are about two inches long, have their own sheath, and attach with velcro.
My computer will not load the videos. Has anyone else had a problem or is it on my end?
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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?
Am I interpeting this correctly?
#138
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Originally Posted by kurt M
...My computer will not load the videos. Has anyone else had a problem or is it on my end?
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.
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Originally Posted by 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?
Am I interpeting this correctly?
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.
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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.
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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.
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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...
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Originally Posted by racergreg
...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.
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.
#143
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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.
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.
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Originally Posted by gbaker
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.
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#145
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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.
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.
#146
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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?
Do you have a non binding guess as to why the R3 loads are higher? Take up time?
What load #s did you see?
#147
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Originally Posted by 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.
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.
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#148
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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?
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?
#149
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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....
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....
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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.
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.
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