mitch236

If you want to know what the current thinking in safety is just look inside a NASCAR car. Full body retention seats, H&N restraints, right side nets. It's a system.

richard glickel.

***

But everyone can afford a neck collar.

ColorChange

Richard, mitch236 is dead right. A neck collar is for comfort, not safety. Even if you can afford it, don't think it will help one bit with regards to safety; it won't.

Geo

CC, we have never been more in agreement.

fatbillybob

Geez Adam, that was one monster hit! I love to hear the success stories but hope never to have to report one of my own. One other issue not addressed is the single use nature of these devices. GBaker said to me once that he thought of these devices as expendable after a big hit. His website goes on to describe what he thinks is big. Isaac is basically a hunk of metal and the dampners either work as your hand can feel them or they don't. HANS is fiberglass and carbon composite mix. I'm pretty sure there are degradeation issues with old FG or CF. Further it is moredifficult to evaluate structural weakness in these kinds of materials. Metals fatique can give you all knids of warning when you reach close to elongation/elastic limits but fail if you go beyond them. Some believe your FG/carbon seats should be changed as well as helmets just because of age alone due to materials degradation. Isaac does not do that.

richard glickel.

BTW, delivery on my HANS device was three business days from on-line order date (can be faster, but UPS ground was good by me).

Ciao!

Richard

Anir

I purchased the Hans. Not knocking the Isaacs, but if the Hans is good enough for F1 loads...

RedlineMan

I don't believe this is true. What is at play here is whether the HANS stays under the belts, and this has proven a debatable point. The ISAAC would also be effected by, not staying under the belts obviously, but by how much they stretched, or perhaps more precisely, how quickly.

Consider where a hangman places the knot for proof that this statement is not correct. I believe a side hit is FAR more lethal because the spine has far less fleixibility in that direction.

Schroth uses very low stretch material, and then adds a "stretch zone" to absorb energy, but also control the total amount of stretch. The two types you speak of would be the older Nylon belts -vs- the more modern Polyester variety. 15-17% stretch compared to 7-10% respectively. Polyester improves MANY aspects greatly. Only the old Simpson belts are Nylon. The new Platinum series are Polyester, and the 6-point camlock and DSL are the absolute cutting edge in restraints. Impact Racing, Bill Simpson's new company, does not specify what type of material they use, at least on their website.

Belt stretch is indeed a large factor in offset seat retention. If your belts stretch dramatically and dump you out of the seat, then you may have problems. If you use Polyester belts with an ultra stiff full containment seat, you have the best system available. A side net is not as "necessary" in this instance, but cannot be argued against for extreme situations.

Those looking for good service and custom ordering at good prices should look at Ultrashield. I have a couple of their seats coming for a customer car, built to his measurements at no extra charge, and I will report back on what I find when they arrive.

richard glickel

I feel, to be on the safe side, that I will be using my HANS together with a Recaro HANS seat (next season - at least that's the plan).

John, make sure to give a report on this new ultrashield seating. Sounds interesting.

BTW, I had the Siimpson platinum belts and returned them - I had a hard time adjusting the belts and went back to a Deist 5-point harness which I have always liked in my 911.

Richard

fatbillybob

redlineman wrote:""Belt stretch is indeed a large factor in offset seat retention. If your belts stretch dramatically and dump you out of the seat, then you may have problems. If you use Polyester belts with an ultra stiff full containment seat, you have the best system available. A side net is not as "necessary" in this instance, but cannot be argued against for extreme situations.""

Crashes always have more than just a one directional fore/aft commponant so minimizing belt stretch is always an issue for proper retention. I have seen people hook belts to the back seat anchors with combos of 4-6 point harnessess. Very Bad IMHO! Is ultra stiff waht you want? I don't think so. OMP with the carbon seats for example claims to have purpose built flex in the seat to help delerate you in a crash. Stiff steat means you hit a brick wall. There is always a trade off with all this stuff. Systems are what these things are all about. You can't just evaluate one product but you have to put the whole package in context. IMO the side net restraint to aid containment and deceleration is far more beneficial that a stiff lateral support seat that helps transmit 100% of the impact to your body. My rude understanding of crash surviveability is that you want enough containment so you don't hit hard things, enough deceleration so you don't fell like you hit a brick wall. So back to the point of the subject HANS and Isaac...the isaac is a speed dependant device and the dampners work in proportion to the crash...it "thinks" if you will. I think that is one of the reasons the ME Isaac user above like this device. The HANS and others are position related devices...your neck on the end of a rope to put it rudely. Your hope with HANS is that at the relative impact you have sustained that the HANS contains your head to your neck and the rest of your system decelerates your body...i.e. seat flex, and belt stretch, and body compression and parts falling off your car to dissipate energy. This is true of Isaac as well but there is a curve in which dampners react to the speed and load upon them before there is complete lock.

RedlineMan

I have studied this quite a bit, and although I am far from being brilliant like the people generating this knowledge, I feel I have a pretty good handle on the latest thinking.

What you have described shows a perfect understanding of the old model of crash dynamics. That is what has been held for many years, and accepted as gospel. However, with the advent of all the sled testing and bio-mechanical engineering associated with it, that model has been abandoned.

As Mitch said, look inside a top flite Nextel Cup Car. NASCAR is the cutting edge right now. Full containment with extreme seat side panels and helmet halos, completely anchored to the chassis, solid as a rock.

The old model theorized that you wanted to decelerate the body slowly so as to relieve the stress of the impact over time. This made a lot of sense intuitively, but crash testing has shown this to be completely falacious, and DANGEROUS.

Kinetic energy is the enemy, and its severity is a function of time. KE=.5MassVelocity^2. The longer the time frame, the more kinetic energy builds. Fatal neck tension loads occur within approximately 30 milliseconds of rapid negative acceleration. That is a blink of an eye. The old model actually INCREASED the severity of the impact because it allowed the body to accelerate for a VERY long time before beginning to restrain it, catastrophically exacerbating the whiplash effect.

This also tended to increase the likelihood that you would contact something solid inside the car. If those items were distant enough to allow your body to accelerate toward them, they hurt really bad!

Todays H&N restraints, low stretch harnesses, and stiff containment seats do not allow kinetic energy that chance to run wild. They stop the body as quickly as is possible. Yes, this does create a violent jolt, but because kinetic energy is not allowed to build, this usually represents a very survivable situation.

Stop the body fast, contain it in as tight a cacoon as possible, and do not allow energy to build. That is the State of the Art

Geo

I think that people who talk about the harshness of the HANS tethers are forgetting that they stretch and this should act not that unlike a damper.

924RACR

John - regarding the effectiveness of the HANS at oblique angles - that's the direct result from testing on the crash sled at Wayne State, as stated directly to me by Tom Gideon, head of safety for GM Racing. If you caught the recent History Channel Modern Marvels show about race safety, he was on it quite a bit. It's just one of the limitations of the device. I do expect that the ISAAC has other limitations of its own; it just hasn't been through as much testing, unfortunately, so we can't say. Trying to stick to the facts here.

Yes, the new stiff webbing is poly, vs. nylon. The downside, as I recall from a conversation with the safety guy at BSR Racing/Safety Devices, poly can of course melt in a fire. So even better is I think they can now make kevlar belts? I remember having the option when ordering the right-side net, but the kevlar was very expensive, so I called for the poly, since it's not right on me, won't drip on me as/if it melts, and only has to work prior to and during the impact, not after. I do not know what the silver Impact belts, et al, are made of.

You guys are correct about the cocoon. Remember the three-impact model of an auto crash. There are three collisions; the car with whatever it hits, your body with belts or car interior, and your internal organs with your bodyshell. It is now all about restraining the driver as much as possible while still allowing them freedom to drive, and the NASCAR boys, as much as we love to slam them for being uncomplicated rednecks, are without question in my mind leading the pack for safety (now that Dale's dead, anyway). There's a lot to be learned there, and while maybe not 100% can be applied to sports car racing, most of it can and should.

But on the seat/RH net thing, it DOES come down to economics. Flat out, a seat alone, no matter how fancy, is not as good as a net. Simple mechanics. The best possible combination is the fancy seat, custom fitted, AND a net. The net costs $80 or whatever. The seat will cost around 10 times that. Which one should you get first??? Again, I need to identify my source in this stuff: this again comes from Tom Gideon, GM Race Safety Engr. You may wish to review my old posts and look where I recounted the details of a presentation he gave to us (Waterford Hills racers) back in the spring.

JCP911S

Bottom line H&N is better than none. Head containment seat is better than no head containment. Net is better than no net.

I think the whole safety debate has elevated the level of protection recently. Time will tell how all these items really perform in real world accidents that have yet to happen, (unfortunately)... some will probably prove themselves more effective, but I have to believe that all of them are a big improvement over the typical arrangement you see today.

I'm just as much in a learning curve as the rest of you, but after discussions like these, some of the stuff I see in people's cars in the paddock makes my blood run cold.....

I'm as big a cheapskate as there is, but $600 for a seat, $900 for H&N, $80 for nets... buy them all...

RedlineMan

Now you know how I'VE felt for years. These forums do indeed bring out a lot of stuff that most people might never think of. A raising of the sum awareness of the driving populace is the worthy result, I'd wager.

I probably come off sounding a bit imperious at times regarding all this stuff. I have no more brains than the average blade of grass, but I do seem to possess good wits regarding how things should be rendered so they are safe, effective, and easy to live with. Not three parameters that often fit together easily. Let me give you all a stunning example of what JCP's quote refers to.

I have a new customer's new-to-him race car in my shop right now. This is a PCA Class E or NASA Class F registered and logged car. It came with Corbeau Forza seats. Absolute junk they are. Well, they are only about $200 new, so you really do get what you pay for with these beauties.

Anyway, they are constructed of a tube perimeter frame, and the space between is filled with formed spring steel "bands" just like you would find in any given OE road seat. They are covered with thin foam and cloth. Not very comfortable, but more to the point, if you took a screw driver, you could jam it right through with very little effort. This car was also fitted with the requisite seat back brace, in this case a nice Brey Krause passive (not attached) bracing pad.

The question that springs to mind is that with nothing approaching a solid surface to support, what did anyone think this brace would contact if the seat moved? In this installation, it should have been termed a "back brace" because there was little proximate to it but the driver's spine! As I mentioned, this setup passed PCA and NASA tech.

How is your blood running?