Hans Devices and DE
06-05-2005, 07:50 PM
#121
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Originally Posted by RJay
Aaaaaaaahhhhh and this is good how? It doesn't matter whether the joint fails or the helmet fails. Its the level the system fails at. A bonded joint will place a pure torsional stress on the helmet, a bolt through will act more through compression. The question is how much pressure can be applied (and over what period) before the helmet fails and is that level likely to be seen in an accident? I can't imagine that currently, it is a design concern for a helmet to deal with torsional stress on outer layers. Despite the concerns about bolt through, theres plenty of real world evidence that the system works. Given the varied construction types of helmets, I'd want to see data on my helmet before I went this way.
In a similar fashion, the same numbers would apply to the tensile strength of the HANS tethers.
06-05-2005, 08:42 PM
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For GBaker re HANS vs Issac
I would assume that the notion of attaching dampers ala the Issac device to a HANS-like support piece has been explored. It seems to me that the HANS would gain some lateral support and the Issac would gain self containment with the attendant removal of the requirement to detach the device from the helmet. Being a mechanical engineer I like the notion of dampers and the Issac seems to be a straightforward means of applying them. As an aside, would there be any benifit or detriment to having dedicated straps rather than the personal harness to attach the dampers to?
Bruinbro
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06-06-2005, 09:48 AM
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Originally Posted by bruinbro
I would assume that the notion of attaching dampers ala the Issac device to a HANS-like support piece has been explored. It seems to me that the HANS would gain some lateral support and the Issac would gain self containment with the attendant removal of the requirement to detach the device from the helmet.
If you download ($12 IIRC) the SAE paper describing the ISAAC, there is a drawing of a device similar to what you described.
Originally Posted by bruinbro
Being a mechanical engineer I like the notion of dampers and the Issac seems to be a straightforward means of applying them. As an aside, would there be any benifit or detriment to having dedicated straps rather than the personal harness to attach the dampers to?Bruinbro
06-07-2005, 10:23 AM
#124
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TD,
>If I understand you correctly, you are saying that a properly operating neck restraint device such as a HANS should largely eliminate the need for window nets, which could make egress more difficult.
Close. I’m saying that the perfect head and neck restraint--which has yet to be invented-—would eliminate the need for such things as head surrounds, side nets and other devices intended to minimize lateral head loads and which have a demonstrated history of retarding egress. (It would also protect against vertical loads and rotational loads about all axes.) Window nets are another matter; they serve to keep one’s arms attached, so they will probably be around for a long time.
For the record, we recommend all Isaac racers utilize right-side nets if they wish to maximize safety.
All H&N restraints reduce head loads in frontal/offset frontal impacts. That’s great, but the extra “safety stuff” needed to address the lateral impact issue is causing problems re egress, and it’s only exacerbated by the SFI Spec. The SFI Spec has this backwards, i.e. a driver should not be required to drag a H&N restraint out the window of a burning car, especially if they have the option of leaving it behind. If they don’t fix this, someone’s gonna get BBQ’d on live TV.
The history of racing safety makes for interesting reading. The first belts were pieces of rope across the cockpit intended to make driving easier by holding the driver in the seat. There was uproar when belts were mandated because many thought that the driver was safer if he were thrown away from the wreck. Sounds stupid now, but there was also a time when basketball coaches demanded players shoot with two hands—after all, everyone knows you can’t shoot with one hand, right?
>Likewise, what you and others may be suggesting is that it is easier for a system like HANS to operate correctly in a very constrained cockpit because it might not be as easy for the device to slip or move at impact.
Exactly, although there have been cases of belt slippage in even F1 cockpits.
>Since I will be driving a NA 944 with full cage and a kirkey deluxe seat (with seat bracing), is there any type of neck/restraint system that might be more effective than others for this specific setup. In other words, could it be that the different brands out perform each other in different situations.
Sure. From the standpoint of measurable head load reduction in near-frontal impacts, the Isaac system and the HANS device are probably the only two high-performance products currently available. The seat-harness combination you describe is well documented, and suggests no particular advantage to one product over the other. Other important issues include convenience, egress, cost etc. The example was given above from the instructor who jumps from car to car, having no idea about the belt placement they may experience. That’s a great observation, and in that case the R3 may work well. We offer a quick-release belt connector pin for racing schools where drivers and instructors are in and out frequently, so that may be an option also.
No manufacturer offers a perfect product, but they have an obligation to assist the racer in making the best choice give their circumstances. The good news is that there is no such thing as a bad head and neck restraint.
>If I understand you correctly, you are saying that a properly operating neck restraint device such as a HANS should largely eliminate the need for window nets, which could make egress more difficult.
Close. I’m saying that the perfect head and neck restraint--which has yet to be invented-—would eliminate the need for such things as head surrounds, side nets and other devices intended to minimize lateral head loads and which have a demonstrated history of retarding egress. (It would also protect against vertical loads and rotational loads about all axes.) Window nets are another matter; they serve to keep one’s arms attached, so they will probably be around for a long time.
For the record, we recommend all Isaac racers utilize right-side nets if they wish to maximize safety.
All H&N restraints reduce head loads in frontal/offset frontal impacts. That’s great, but the extra “safety stuff” needed to address the lateral impact issue is causing problems re egress, and it’s only exacerbated by the SFI Spec. The SFI Spec has this backwards, i.e. a driver should not be required to drag a H&N restraint out the window of a burning car, especially if they have the option of leaving it behind. If they don’t fix this, someone’s gonna get BBQ’d on live TV.
The history of racing safety makes for interesting reading. The first belts were pieces of rope across the cockpit intended to make driving easier by holding the driver in the seat. There was uproar when belts were mandated because many thought that the driver was safer if he were thrown away from the wreck. Sounds stupid now, but there was also a time when basketball coaches demanded players shoot with two hands—after all, everyone knows you can’t shoot with one hand, right?
>Likewise, what you and others may be suggesting is that it is easier for a system like HANS to operate correctly in a very constrained cockpit because it might not be as easy for the device to slip or move at impact.
Exactly, although there have been cases of belt slippage in even F1 cockpits.
>Since I will be driving a NA 944 with full cage and a kirkey deluxe seat (with seat bracing), is there any type of neck/restraint system that might be more effective than others for this specific setup. In other words, could it be that the different brands out perform each other in different situations.
Sure. From the standpoint of measurable head load reduction in near-frontal impacts, the Isaac system and the HANS device are probably the only two high-performance products currently available. The seat-harness combination you describe is well documented, and suggests no particular advantage to one product over the other. Other important issues include convenience, egress, cost etc. The example was given above from the instructor who jumps from car to car, having no idea about the belt placement they may experience. That’s a great observation, and in that case the R3 may work well. We offer a quick-release belt connector pin for racing schools where drivers and instructors are in and out frequently, so that may be an option also.
No manufacturer offers a perfect product, but they have an obligation to assist the racer in making the best choice give their circumstances. The good news is that there is no such thing as a bad head and neck restraint.
06-07-2005, 10:32 AM
#125
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Originally Posted by ltc
..."Smack your hand on your forehead and ask why I didn't think of it sooner"....all engineers have had these moments....mine usually come at 3AM when I'm pacing the house thinking.
06-07-2005, 12:33 PM
#126
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Originally Posted by gbaker
...or right after walking past the shock display in the local auto parts store.
