A H&N restraint is basically an extension to your helmet which protects your neck in a collision. It lowers the strain on your neck to a level that hopefully avoids a basilar skull fracture. Once you secure your body in a car with a harness then your head is still 'floating' and unrestrained (except by your neck!). You are also wearing a helmet which adds mass to the already substantial mass of your head. Given the body is restrainted by harnesses and your head is only restrained by your neck then the neck will have a serious load placed on it in a front or side impact. Remember, your harnesses need to support 3000lbs of force. You're neck can't do that. A Head and Neck restraint is designed to absorb that energy so the neck load is reduced substantially.
50% of racing deaths are caused by basilar skull fractures. Isaac claims that this type of injury occurs at 4000 newtons or 900 pounds of force on your neck. All certified H&N's will limit the load on your neck to less than this in a 70G impact.
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There are two standards for these devices
All the tests seem to have some issues. Some device makers claim a test doesn't allow their device to be tested despite the fact that they exceed the test requirements. The other thing is some race series require approved certified devices rather than any device thats certified.
The new standard is set very high by NASCAR’s SFI 38.1 Head and Neck restraint specification. In order to pass the specification, the restraint now has to pass a 70 G, 30 degree angular frontal impact, as before, and three straight frontal 70G impacts below 4000 N neck Tension. (The Federal Motor Vehicle Safety Standards for passenger cars allows 4170 N.) To pass, a device has to show good results in limiting maximum upper neck tension, maximum upper neck compression and maximum NIJ. The latter seems to be a composite factor that takes into accoutn not just loads but moments. I think the lowest possible NIJ is the goal not just a one-off good tension or compression number.
Most devices can be tested for SFI 38.1, however, Isaac claim the test is flawed and as a result their device cannot be certified. Here is what Greg Baker from Isaac said when asked why all Isaac designs have not been submitted for such certification,
"We think there is a fundamental flaw in the SFI design. There is a section of the SFI Spec 38.1 (single point release) that calls for a specific design criteria which requires the driver to drag the restraint out the window. That's where the problem begins. The only time a head and neck restraint has trapped a driver in a car , burning or otherwise, is when is has been an SFI design. The SFI specification calls for a certain performance level. The question is are all Isaac products good enough to meet SFI test criteria and the answer is yes. We will certify Isaac products to meet or exceed SFI performance levels, but we won’t sell anything that can trap them in a burning car."
So, if true, this looks a similar issue to why only Hans can be tested for FIA 8858, but the way the FIA, NASCAR and a whole bunch of other serious racing saftey guys act seems to suggest that this argument may not have merit.
This test was created by the FIA once they were convinced that HANS devices were the only thing that really works. Therefore, Hans is the only device to pass this test right now. The reason only Hans passes the test seems to be because only a Hans shaped device can even be tested by the FIA. Something like an R3 is not testable because the FIA do not think it worthwhile, otherwise they woud create a test like they did for the Hans. Apparently, discussions are ongoing to try and fix the test so that a non Hans device can actually take it, but the R3 has been around a long time now and the FIA have not moved to do anything yet.
First, almost any H&N device is better than no device. That said, the following charts shows the reduction in neck strain when using a H&N. These results are from LFT Tech and Hans and show the each device in both angular and frontal tests. 4000 newtons is the accepted injury level and as is clear from the chart, most H&N devices significantly reduce the load on the neck. I have not seen Hans claim any kind of side impact protection which is usually what R3 will claim as a major advantage of R3 against Hans. As a rule, Hans outperforms all others.
The difference between these pictures is that the R3 chart shows an angular impact of 30 degrees whereas the Hans shows a direct frontal impact. The Hans does outperform the older R3 devices in the frontal scenario. The R3 after August 2005 was improved by around 20% in the frontal (so it should be around 80% of 680 on new ones) changing the position of the clips on the helmet and where the tether attaches to the R3. LFT said not to attempt to modify an older R3. The 2007 R3s now beat the Hans in sled tests for frontal as well as angular impacts.
| 70G R3 Angular Impact | R3 vs Hybrid vs HANS neck tension & net tests (2007 Models) |
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At the 2006 SCCA Convention in Kansas City, the independent experts at the safety seminar emphatically stated that the HANS device works better in the SFI certification tests than any other SFI certified products, and better than any other product in real life situations. They have sold over 20,000 of them and the safety experts at NASCAR and FIA seem convinced. Apparently, HANS do not publish their offset test results as the experts focus on the frontal test and use the offset test to ensure nothing odd is going on. I guess this is the reason that there are more frontal tests in the SFI test. With all the testing that NASCAR has done since Earnhardt's death, they probably know what works and what does not. I have to say that while I am skeptical about any manufacturer's claims for their products, I am very deeply skeptical about a manufacturer's claim about a competitor's device - it just is not unbiased.
It's also clear that both Hans and LFT Techs R3 regard each other as the their major competitors. Isaac, which claims it can meet the performance requirements of the testing but is not certified to SFI, looks like a distant third or forth place runner.
Why do the tests use 70G? An accident that delivers 70G to the driver is an absolutely enormous impact. A 45G impact puts a load of around 2500lbs on each shoulder strap so 5000lbs against your body. They picked 70G because of a Sports car accident with Christian Elder where he hit a wall with the A and B pillars of his cup car. This is a hugely strong area of the car and this resulted in a 70G shock to the driver as that section did not deform to help absorb the hit. This lead to 70G being the shock level used for these tests. SFI 16.1 nylon seat belts have broken in 70G sled testing (11000lbs breaking strength). As an example, Dale Earnhardt died with a 42G angular impact with a delta-V of 38mph.
A 70G driver shock in a normal road car will probadly mean an accident big enough to disintegrate the car. These tests use forces way above whats survivable in a normal road car. Plus, road cars deform to absorb the impact, this makes such a high G event more rare. Indy cars and formula 1 cars etc have very stiff passenger cells and if the cell collides with an object, the passenger will experience a high G incident as the energy will be passed through to the driver. Bodies like NASCAR and Indy are now using soft wall technology on their tracks which seems to half the G of a wall strike when compared with the older hard walls. Ralf Shumacher is probably thankful of this when he struck a soft wall at Indy in 2004.
They should protect you as long as the car protects you. If the impact compromises the passenger compartment or the car explodes then a H&N won't help you. If the impact is such that the car doesn't collapse and you have good belts, mounts, etc then a H&N will be effective. A proper race car is substantially stronger than a normal road car. As usual, the best advice is lets not find out.
One newton can accelerate a kilo at a rate of 1 meter per second. That is, a one Newton force on a 1 kg object results in an acceleration of 1 m/s^2. One newton is the same as 0.22481 pounds of force (4.4N is 1 pound of force).
So, 4000 newtons on an 80 kilogram person results in an acceleration of 50 meters per second squared. 1G is 9.8m/s^2. So, 4000 newtons on an 80 kg person results in an acceleration force of around 5G on the person.
These tests don't measure 4000 newtons on the person, they measure it on the neck and the neck/head weighs a lot less than a person so 4000 newtons on just the head/helmet will accelerate it by a much higher G than 5G. Lets say your head weighs 5kgs then 4000 newtons will accelerate it by around 80G if it was free to move.
(I'd like this information checked by someone with an engineering background if possible)
Heres anarticle on newtons.
This seems hard to say. The government uses 4160 newtons as the 40% chance of injury level. SFI and FIA use 4000 newtons as the pass mark. How many newtons your neck can take depends on:
A concern may be that in some sports like drag racing, you can see much older drivers than in other sports and this makes them more prone to neck injuries even with good safety equipment because of their age.
Isaac, a manufactuer of H&N restraints says that 4000 newtons is the level at which a basilar skull fracture occurs.
Price US 865.
Certifications: FIA 8858, SFI 38.1
Web site:http://www.hansdevice.com
Belt System: Any SFI or FIA multi-point harness - absolutely no need to buy anything new.
This is probably the most well known device givens it's the only one approved in NASCAR and all FIA sanctioned events. This is a yolk type device made of carbon fiber which goes behind the neck and then have two 'legs' that go over the front of the shoulders down your chest. Your 5 or 6pt harness then goes over the top of these legs and secures it. It has easily detachable helment anchor system for its tethers that is blessed by Snell. There is also a quick disconnect tether option for those that want it. It's FIA and SFI 38.1 certified.
In regular driving the Hans does not restrict head motion. Its tethers tighten up as the drivers multipoint harness stretches in a crash. The other restraints do have to be worn tighter or you have to turn your head against a damper.
This device requires a multipoint harness system.
Price US 995
Certifications: SFI 38.1
Web site:http://www.lfttech.com
Belt System: 3pt, 5pt ot 6pt. Any SFI harness will work.
This looks like a carbon fiber cross. The cross goes against your back and kevlar straps secure it to your chest. It requires D rings to be installed on your helmet. It's SFI 38.1 certified. It works in a car with a 3pt belt also.
This device works well for instructors as you wear it and it works with both 6pt and 3pt belt systems, although whether anyone needs a device when the body is not really restrained has not been proved.
Price: US 750
Certifications: SFI 38.1
Web site:http://www.hutchensdevice.com/home/hutch2.html
Belt System: 3pt, 5pt ot 6pt. Any SFI harness will work.
This is a combination climbing style web harness and carbon fiber system, similar to a climbing harness with straps at the top to attach to your helmet.
This looks like it would work for instructors given you wear it, but there does not seem to be any unbiased performance information.
Price: US 1050
Certifications: SFI 38.1
Web site:http://www.lfttech.com
Belt System: 3pt, 5pt ot 6pt. Any SFI harness will work.
This is a combination climbing style web harness and carbon fiber system, similar to a climbing harness with straps at the top to attach to your helmet.
This looks ideal for instructors and students and now has SFI tests showing it is superior to the 2005 Hans devices for frontal impacts. It's not clear what advantages it would have over an R3.
Price 895
Certifications: None
Web site:http://www.isaacdirect.com
Belt System: 5pt ot 6pt.
This is a unique design in that it uses a pair of dampers or shocks attached to the shoulder belts and the helmet. The dampers limit the load on the head and can be quickly removed from the helmet using two buttons on the dampers. It's claimed that this makes egress from a damaged car easier as you are not wearing the restraint, but there is a whole bunch of clunky hardware attached to the helmet which still causes a concern. Isaac claims the best results on the marketing in testing and claims it exceeds SFI 38.1 levels BUT they are not certified. The reason they aren't certified seems to be they don't provide a single point release, but without independent verification it is difficult to know what the truth is. See the standards section for more info.
Isaac have tested their device in what they claim as identical conditions to those used to test Hans for SFI 38.1. They claim they pass but can't certify due to the single restraint provision in the SFI 38.1 test.
These results look very good when compared with the tests performed on other devices, but they are Isaac's numbers and look nothing like the offical SFI data that other manufacturer's publish or are detailed in SAE research papers.
Isaac is the only device that can be glued to your helmet. This avoids the need to drill holes. This sounds like a poor mounting approach but they say their adhesive is used on missiles and has a load rating of several times the expected loads. It also means no screws to loosen, but you do have to strip off paint around the mounting points which seems at odds with trying to make things safer.
This won't work for instructors given the dampers need to be secured to the shoulder harnesses and there's rarely time to do this at a HPDE event.
The angle from the shoulder belts to the harness is more critical when a H&N is used. You need to check the instructions with the device but as close to 0 degrees seems the best and is the best case also even with no H&N. I'm told that a steeper angle pushes the H&N device forward which allows the head to accelerate more before the neck tethers restrain the head.
The way you wrap your shoulder harnesses around the harness bar may also be different than normal so check the installation instructions for that.
LFT Tech said they work well together. The H&N will slow the head down allowing the bag to inflate more. This is better than the head moving forward before the bag is fully inflated which results in the head being thrown backwards. The FIA showed some work that they had done on airbags at the SCCA safety seminar in February 2006. They seemed to say keep the airbag energized but do not wear a helmet with anything that could catch on the airbag as it inflates which could cause the helmet to be tipped upward at the fornt - i.e. no firmly attached peaks liek you see in some rally helmets and keep the visor closed (they also said wear a HANS.) Another possibility is that your raised visor can puncture the airbag and then it would deflate in to your view port, not good. So, put the visor down or remove it.
Angular impacts statistically are the most common impacts at a track. Therefore, it will pay to make sure you've taken steps to improve your protection in this area. All H&Ns also restrict the heads lateral motion in an angular impact. However, this protection should be augmented with one or more of the following if possible:
These all help to limit the lateral motion of the driver in a side impact/angular impact and keep you in place.
These containment modifications will also help improve any H&N device performance and containment is a critical part of any safety system.
It's now possible to buy Helmets with Hans clips preinstalled from Bell, Simpson, Arai, Impact, a company called Suomy (rally helmets I think), Peltor, Stilo, OMP and a whole bunch more. These clips areNOT safe when using with other devices besides Hans. Different H&N devices are different heights behind the neck and the tethers are different lengths. This means different mounting points on the helmet for each device. I've also seen the helmet hole positions change year by year for a given device, for example, the R3. So, if you buy a used helmet with the D links already installed then double check that they are in the right place for your device even if the previous owner had the same device.
Other helmets or different systems require you to drill holes in the helmet to attach the D hooks for the tethers (the Hans system uses what looks to be a highly engineered attachment system which is easy to use but very different from the D hooks most others seem to use). The restraints usually come with a kit containing screws, a template and two D hooks and you need to drill holes in the helmet to attach the D hooks. Many dealers won't do it for you because of liability, but most Hans dealers do offer this service though. It looks to be part of the training Hans gives its dealers. LFT Tech will also modify your helmet. But, don't be surprised when you find out that you need to make holes in the helmet.
Newer Bell helmets now make adding the holes much easier than older ones. They modified the stuffing of the helmet to make putting in the washers/nuts on the inside of the helmet a lot easier.
Isaac customers can now use an adhesive to attach the system to a helmet.
Once a helmet has had a set of holes drilled then it looks like if you need another set of holes for a different device then you need a new helmet.
Based on the evidence I've seen and most of that is in this article then this is what I'd conclude.
