Tried an ISAAC
02-22-2005, 09:37 AM
#46
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Didn't think my simple post would start a Holy War.
I have a simple question(s). Why doesn't HANS offer a weekend rental program? Is it because they don't have to since their device is considered the "standard" or is it something else?
Sure would be nice to try both, since it seems both will keep your head attached to your body during an accident. Isn't that really the bottom line!?
I have a simple question(s). Why doesn't HANS offer a weekend rental program? Is it because they don't have to since their device is considered the "standard" or is it something else?
Sure would be nice to try both, since it seems both will keep your head attached to your body during an accident. Isn't that really the bottom line!?
02-22-2005, 09:37 AM
#47
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This argument is completely useless. I am a physician. That does not make me any more of an authority than an engineer. In medicine, we use very well setup studies and then analyze the outcome data. Nobody here is offering any hard data comparing the HANS with the Isaacs. This is all conjecture. Someone should setup a crash test and study these devices. Then the argument will make more sense. My theory is that both devices will work at reducing fatalities and both are definately better than nothing. One may prove to be better than the other in certain circumstances, but I doubt that one will prove to be the clear winner. Then again, I may be proven wrong -the point is that nobody has PROVEN anything yet.
But as to which one I would choose at this moment, it would be the HANS because of the 38.1 certification. I am confident that the Isaacs would pass as well, but it hasn't as of yet and that leaves a big question mark on its value.
But as to which one I would choose at this moment, it would be the HANS because of the 38.1 certification. I am confident that the Isaacs would pass as well, but it hasn't as of yet and that leaves a big question mark on its value.
02-22-2005, 09:59 AM
#48
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Geo - if head location or displacement is the issue, why are all the tests (*including 38.1 IIRC) concerned with neck tensile loads? Unless that's perhaps a more convenient way of measuring than displacement. Still, I doubt a compromise for convenience would be made in this area.
As for ISAAC mounting style; I used the bolts on my first helmet/ISAAC - worked great when I used them. I now have the glue for my new helmet, preferred it to the bolts, lower maintenance. If you read your documentation, the bolts should be checked periodically for tightness. I never made it far enough with the first drilled helmet to need to check torques.
Yes, theoretically us engineers might expect the dampers to do a better job than webbing. But this has not been shown IMO to be the case in actual sled tests in a statistically significant manner (as I mentioned previously).
Final note <rant>: DAMPERS DAMPERS DAMPERS!!! We are not watering our head restraints! Please don't call them dampeners, they don't soak you, they don't dampen motion! They damp it!!! </rant>
As for ISAAC mounting style; I used the bolts on my first helmet/ISAAC - worked great when I used them. I now have the glue for my new helmet, preferred it to the bolts, lower maintenance. If you read your documentation, the bolts should be checked periodically for tightness. I never made it far enough with the first drilled helmet to need to check torques.
Yes, theoretically us engineers might expect the dampers to do a better job than webbing. But this has not been shown IMO to be the case in actual sled tests in a statistically significant manner (as I mentioned previously).
Final note <rant>: DAMPERS DAMPERS DAMPERS!!! We are not watering our head restraints! Please don't call them dampeners, they don't soak you, they don't dampen motion! They damp it!!! </rant>
02-22-2005, 10:03 AM
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Originally Posted by mitch236
This argument is completely useless. I am a physician. That does not make me any more of an authority than an engineer. In medicine, we use very well setup studies and then analyze the outcome data. Nobody here is offering any hard data comparing the HANS with the Isaacs. This is all conjecture. Someone should setup a crash test and study these devices. Then the argument will make more sense. My theory is that both devices will work at reducing fatalities and both are definately better than nothing. One may prove to be better than the other in certain circumstances, but I doubt that one will prove to be the clear winner. Then again, I may be proven wrong -the point is that nobody has PROVEN anything yet.
But as to which one I would choose at this moment, it would be the HANS because of the 38.1 certification. I am confident that the Isaacs would pass as well, but it hasn't as of yet and that leaves a big question mark on its value.
But as to which one I would choose at this moment, it would be the HANS because of the 38.1 certification. I am confident that the Isaacs would pass as well, but it hasn't as of yet and that leaves a big question mark on its value.
You are likewise right about the latter (38.1); I think the VHS/Beta analogy may turn out to be better than I'd like to admit!
02-22-2005, 10:13 AM
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Here is the data for all of you who don’t believe/understand the argument. I will post one picture (I am probably breaking a copyright but I really don’t think SAE or ISAAC will care, considering I am advertising their products). Here is a shot of the test sled, and the paper includes actual data.
Here is the paper. It's about $10 for members.
http://www.sae.org/servlets/Maintain...PROD_TYP=PAPER
Here is the paper. It's about $10 for members.
http://www.sae.org/servlets/Maintain...PROD_TYP=PAPER
02-22-2005, 10:45 AM
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Hey Tim, those shocks are mounted at a very different angle than shows on their website. From the angle shown, it appears that they would be at maximum effectiveness for head-on collisions, and minimally effective (just like Hans) for side impacts. Can you shed any light on this?
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2016 Ford Transit Connect Titanium LWB
2018 Tesla Model 3 - Electricity can be fun!
Retired Club Racer & National PCA Instructor
Past Flames:
1994 RS America Club Racer
2004 GT3 Track Car
1984 911 Carrera Club Racer
1974 914/4 2.0 Track Car
CLICK HERE to see some of my ancient racing videos.
02-22-2005, 10:54 AM
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Larry, good instight and I agree a little. This is a picture of one of their first trials. The angle seems the same as I have mounted on my helmet, but my concern is that the other end of the dashpots do not look like they are mounted to the belts with rollers, but are instead firmly clamped to the belts. This is very different data than our set-ups. Further testing used the rollers but not complete data was shown. I am going to ask Gregg about this as the data still looks comparable and this surprises me.
Regarding side impacts, you still get some benefit because the one shock under extenstion will be helping to slow and maybe even the shock under compression might help, but I don't know how significant these will be.
Regarding side impacts, you still get some benefit because the one shock under extenstion will be helping to slow and maybe even the shock under compression might help, but I don't know how significant these will be.
02-22-2005, 11:03 AM
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Ahhhh we have the previously mentioned CRASH EXPERT EXTRAODINARE.
Gregg: Can you comment on why the data looks significantly better with the roller apparatus than the fixed clamp on the belts? This surprises me.
Gregg: Can you comment on why the data looks significantly better with the roller apparatus than the fixed clamp on the belts? This surprises me.
02-22-2005, 11:11 AM
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Originally Posted by ColorChange
Mark:
No offense intended, simply direct and accurate communication. In my second comment, I should have said your concerns are wrong or based upon wrong assumptions/understanding. My mistake and I apologize.
Here are some more facts and data for you.
For additional information on how various systems perform, check the SAE web site at http://www.sae.org. Extensive comparative testing was conducted during the summer of 2002, the results of which were presented at the SAE's Motor Sports Engineering Conference in December 2002 and are available as an SAE technical paper (Paper Number 2002-01-3304). Also available is the SAE technical paper titled "The Use of Dashpots in the Prevention of Basilar Skull Fractures" (Paper Number 2002-01-3306), which describes the development of the Isaac® head and neck system. These papers can be downloaded from the SAE web site for a modest copyright charge.
While I agree that blindly assuming a product is safe because of our legal system is insane, I know some of the people at ISAAC as a result of my purchasing investigation and have read their papers. The people involved are credible, and I think the product is sound, although neither of us are biomechanical crash test engineers.
Just for the record, what is a dumping situation?
ltc, you must be an engineer.
No offense intended, simply direct and accurate communication. In my second comment, I should have said your concerns are wrong or based upon wrong assumptions/understanding. My mistake and I apologize.
Here are some more facts and data for you.
For additional information on how various systems perform, check the SAE web site at http://www.sae.org. Extensive comparative testing was conducted during the summer of 2002, the results of which were presented at the SAE's Motor Sports Engineering Conference in December 2002 and are available as an SAE technical paper (Paper Number 2002-01-3304). Also available is the SAE technical paper titled "The Use of Dashpots in the Prevention of Basilar Skull Fractures" (Paper Number 2002-01-3306), which describes the development of the Isaac® head and neck system. These papers can be downloaded from the SAE web site for a modest copyright charge.
While I agree that blindly assuming a product is safe because of our legal system is insane, I know some of the people at ISAAC as a result of my purchasing investigation and have read their papers. The people involved are credible, and I think the product is sound, although neither of us are biomechanical crash test engineers.
Just for the record, what is a dumping situation?
ltc, you must be an engineer.
OK, just to be sure I understand this argument, I have downloaded and read three papers from the SAE site. The two listed here and paper #2004-01-3516 which is a revisit of the earlier comparison paper from 2002.
Firstly, I didn't see any of the above graphic comparisons. None of the three papers compare the HANS with the Isaacs. I stand with my assertion that the debate about the superiority of Isaacs over the HANS has not been addressed.
Also, what do the shadings in the bars represent?
02-22-2005, 11:46 AM
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Gentlemen,
Rather than comment on specific issues brought up over these pages, let me address some general themes.
There are two truths in life with respect to H&N restraints:
1) There is no such thing as a bad H&N restraint. They all work. Some work better than others.
2) Basilar Skull Fracture (BSF) has nothing to do with head position. Absolutely, positively nothing.
BSF, as the name implies, is the injury caused when a pulling force of approximately 900 pounds is applied at the junction of the upper neck and the base of the skull. It happens when the body stops and the head keeps going. It is sometimes referred to as a Hangman’s injury. Once the bony structure of this region is compromised any remaining energy must be absorbed by critical soft tissue such as the carotid arteries or the spinal column. A severed spinal column unplugs the brain from the heart, and the heart stops before the car stops. Severed carotid arteries fail to provide blood to the brain and death occurs more slowly. In either case the driver is probably unconscious.
There are some safety implications regarding head “excursion”, as some call it, but these are secondary matters and not effectively addressed by any product.
Belt dumping:
An Isaac system will not cause belt dumping.
Tether length and the HANS device:
The longer the tethers the higher the head loads. We don’t know how much as this has never been tested as a crash sled variable. However, it is obvious that with, say, 50’ tethers the device will not work at all. If you own a HANS device, do not play with it. Also, it is true that on impact the rigid portion of the HANS device will move toward the rear, shortening the effective length of the tethers.
Dampers vs tethers:
An Isaac system uses dampers to hold your head on; the HANS device uses tethers to hold your head up. The Isaac system’s dampers respond to velocity to limit kinetic energy. It is a passive mechanism that works only when you crash. They both work very well; they just work using different principles.
Brain slosh (how’s that for a technical term?):
Given presentations at the SAE’s Motorsports Engineering Conference in December, with the possible exception of rotational loads, it probably doesn’t matter what product you use. It was thought that limiting head “excursion” could reduce the chance of hitting the wheel with your helmet, but the fact is you’re probably going to hit the wheel anyway in a big crash, and be temporarily rendered unconscious. It’s common for HANS device users to get knocked out in high-speed professional series. We never had this happen to Isaac users until about three weeks ago when a driver hit a stalled car at Sebring so hard he was airlifted to Tampa General with a fractured L1 vertebra (no head or neck injuries). He was out for a “minute or so.”
Relative performance:
Mitch, SAE papers 2002-01-3304 and 2002-01-3306 compare four products using the same crash protocol. These were the sources of most of the data in the chart Tim posted. Same lab, same sled, same dummy, same crash pulse, etc.
Experts:
Most research experts in this field have been involved in the development of the HANS device since the late ‘80s. Ironically, they had nothing to do with the first H&N restraint developed by George White in 1979, which BTW, is a very good product.
SFI Spec 38.1:
http://www.isaacdirect.com/SFI.html
Rather than comment on specific issues brought up over these pages, let me address some general themes.
There are two truths in life with respect to H&N restraints:
1) There is no such thing as a bad H&N restraint. They all work. Some work better than others.
2) Basilar Skull Fracture (BSF) has nothing to do with head position. Absolutely, positively nothing.
BSF, as the name implies, is the injury caused when a pulling force of approximately 900 pounds is applied at the junction of the upper neck and the base of the skull. It happens when the body stops and the head keeps going. It is sometimes referred to as a Hangman’s injury. Once the bony structure of this region is compromised any remaining energy must be absorbed by critical soft tissue such as the carotid arteries or the spinal column. A severed spinal column unplugs the brain from the heart, and the heart stops before the car stops. Severed carotid arteries fail to provide blood to the brain and death occurs more slowly. In either case the driver is probably unconscious.
There are some safety implications regarding head “excursion”, as some call it, but these are secondary matters and not effectively addressed by any product.
Belt dumping:
An Isaac system will not cause belt dumping.
Tether length and the HANS device:
The longer the tethers the higher the head loads. We don’t know how much as this has never been tested as a crash sled variable. However, it is obvious that with, say, 50’ tethers the device will not work at all. If you own a HANS device, do not play with it. Also, it is true that on impact the rigid portion of the HANS device will move toward the rear, shortening the effective length of the tethers.
Dampers vs tethers:
An Isaac system uses dampers to hold your head on; the HANS device uses tethers to hold your head up. The Isaac system’s dampers respond to velocity to limit kinetic energy. It is a passive mechanism that works only when you crash. They both work very well; they just work using different principles.
Brain slosh (how’s that for a technical term?):
Given presentations at the SAE’s Motorsports Engineering Conference in December, with the possible exception of rotational loads, it probably doesn’t matter what product you use. It was thought that limiting head “excursion” could reduce the chance of hitting the wheel with your helmet, but the fact is you’re probably going to hit the wheel anyway in a big crash, and be temporarily rendered unconscious. It’s common for HANS device users to get knocked out in high-speed professional series. We never had this happen to Isaac users until about three weeks ago when a driver hit a stalled car at Sebring so hard he was airlifted to Tampa General with a fractured L1 vertebra (no head or neck injuries). He was out for a “minute or so.”
Relative performance:
Mitch, SAE papers 2002-01-3304 and 2002-01-3306 compare four products using the same crash protocol. These were the sources of most of the data in the chart Tim posted. Same lab, same sled, same dummy, same crash pulse, etc.
Experts:
Most research experts in this field have been involved in the development of the HANS device since the late ‘80s. Ironically, they had nothing to do with the first H&N restraint developed by George White in 1979, which BTW, is a very good product.
SFI Spec 38.1:
http://www.isaacdirect.com/SFI.html
02-22-2005, 11:58 AM
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Originally Posted by ColorChange
Gregg: Can you comment on why the data looks significantly better with the roller apparatus than the fixed clamp on the belts? This surprises me.
Because the body moves so far out of the seat in a crash, clamping the belt connection rigidly to the belt tended to yank the head back. We never killed the dummy, but loads were higher than necessary.
The rolling belt connector allows the lower portion to follow the shoulders forward during the crash. Ideally, one would connect the lower portion directly to the driver's scapula with a big lag screw, but we knew demand for that model would be low so we didn't bother.
02-22-2005, 11:58 AM
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Originally Posted by gbaker
A severed spinal column unplugs the brain from the heart, and the heart stops before the car stops.
02-22-2005, 12:03 PM
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Originally Posted by mitch236
Also, what do the shadings in the bars represent?
02-22-2005, 12:03 PM
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Ahhhh ... makes sense. Thanks Gregg.
Mitch. Seriously? The heart will continue to fire without the brain? Does it do this going to the spine and then directly back like an involuntary response when pulling your hand away from the fire?
Mitch. Seriously? The heart will continue to fire without the brain? Does it do this going to the spine and then directly back like an involuntary response when pulling your hand away from the fire?