gbaker

(Just an FYI.)

From Tom Gideon of GM Racing Safety:

"The difference between the six-point and the five-point harnesses are below the waist, but the benefits from the six-point are actually seen in the chest area," said Gideon. "The five-point has a single crotch strap. Six-points have two straps that come from the lap belt and wrap around the legs, connecting under the driver. As the driver moves forward in a frontal impact, the pelvis is restrained better with the six-point. By restraining the pelvis, there is less energy for the shoulder harness to absorb, keeping the chest from being compressed.

"For example, in a crash at 30 miles an hour you get two inches of chest compression with a five-point but only one inch of compression with a six-point. As a result you see fewer sternum fractures and rib fractures than you would have with a five-point harness."

Found here.

sjanes

"The six-point safety harness, already used in open-wheel racing, replaces the five-point harnesses used up until the end of 2006"

The Na$tyCar boys have been using 5pt?

Thanks for the link Gregg.

chrisp

I'm not sure I fully grasp. Is he saying that it's best to sit on the sub straps and share mounts with the lap belts rather than route them through the hole in the bottom of the seat?

ltc

IIRC, Mr Gideon's recommendation of a 6 point over a 5 point has been discussed here over three years ago.
https://rennlist.com/forums/racing-and-drivers-education-forum/126126-notes-from-presentation-by-tom-gideon-gm-race-safety-eng.html

Subsequent searches in this forum for 'Gideon' will return about a dozen more threads discussing this.

As for 'sitting' on the subs, it too has been discussed before and has been compared to this harness design (used in type open cockpit/reclined seating position cars IIRC)
http://www.teamtechmotorsports.com/r.../jetpilot.html

And the IRL version:
http://www.teamtechmotorsports.com/r...s/indycar.html

Gregg,
Thanks as always for the posts and info.

RedlineMan

Hey;

This is a proven advantage of 6-point cradle -vs- a single sub. It's the old KE thing again. Quick hip control is the foundation that produces lower overal KE numbers, which translates to less force throughout the system. Chest loads being reduced is a part of that. Interestingly, upright seating positions also reduce chest loads.

http://www.redlinerennsport.com/CrashBiomechSub.pdf

I have not read the link yet, but any sub system that increase hip rotation control will offer this benefit to one degree or another. When you get to cradle type arrangements, the differences are largely in comfort. Even a V-sub that is sat on will offer some portion of this benefit, depending on how tight you wear it. That would be the, ummm... rub.

As I said to someone else recently, if you are sitting on a cradle sub setup, and it is not uncomfortable, that is probably a good sign that it is not tight enough!

gbaker

Geez ltc, you make me look like a piker with all those references.

I found this a good summary of the whole KE/loose-vs-tight belt/gradual deceleration thing. Odd that the article was not dated.

ltc

Combination of insomnia, OCD and idiot savant....I've learned to live with it!

Geo

John, do you have reference to research that supports this?

The reason I ask is that I prefer a more reclined seating position, but until I see a reference to scientifice research on the matter I'm not changing my preference.

I haven't seen any research that specifically differenciates between the different 6-pt harnesses. Can you point me in that direction?

sjanes

"Six-points have two straps that come from the lap belt and wrap around the legs, connecting under the driver."

I think what he is saying is that the subs mount to the lap belts at the camlock , wrap around the legs, go through the seat and mount under the seat (such as the Schroth Hybrid).

RedlineMan

Hey G;

The source for these particular points is Dr. Melvin, I believe. He of the extensive open wheel experience where it pertains to seating angles. However, I am not sure that he - or anyone - has put it all together in such a fashion for public consumption. To some extent it may be my culling of so many different sources to put together a coherent step-by-step timeline of what happens, with gaps filled in by my own thought on things. This filler is more in the way things are explained, and analogies, not the core information. If I went and rooted around, I could get you quotes.

Rest assured ALL of the "knowledge" behind my pontificating on these matters comes from PROFESSIONALS in the field. I'm just the Town Crier.

Geo

John, I appreciate the response. I have no hidden agenda. I just haven't read anything specifying a particular type of 6 point nor anything dealing with the effect the seat angle has. My preference is like yours - to read the technical document(s) directly thanks.

RedlineMan

Now...

Regarding what Dr. Melvin said. He stated that open wheel cars had come a long way in side impact protection, but had some ways to go in terms of forward retention of the driver, and that the seating position had a lot to do with that. The layback position was a real problem in that respect, and that sedan type seating positions where the driver was much more upright were far easier to control.

In another portion of what I have seen quoted, he was describing what had been learned about hip control. This is what I referenced in the blurb I linked to.

He also talked about belt systems, the Formula style having been developed specifically for open wheelers where the crotch strap was more or less doing most of the work in a very direct and active way. He also mentioned the lack of comfort therein.

Now, this is where I come in. His comments are in a lecture setting, and sometimes a bit disjointed or fractured by random segues, off-topic forays, and questions from the audience. I take the hip control portion of his comments, then the seating angle, and the importance of proper lap belt control, and I roll it around in my head and come up with a step-by-step scenario of how the system functions, minus all the extraneous stuff of a lecture setting.

If the lap belt is the foundation block of the safety system, the sub is the mortar. The sub allows the blocks to do their job most efficiently. The blocks would still work alone to some degree, but not as effectively as with the mortar there.

The angle of the body essentially governs how much mass in above or below the lap belt. If you have a declined position, much more mass will naturally follow a forward path under the lap belt. A more upright position will tend to throw more mass OVER the lap belt. The more upright you are, the more the lap belt becomes a pivot, or fulcrum.

With quick hip control - meaning a rapid stop of hip sub-rotation - and good lap belt control - kept as low as possible - the length of time it takes for the torso to "hit" the shoulder straps fully is reduced. This is the KE -vs- Time relationship again, and this rapid resonse scenario lessens them both. With the layback seating position, the amount of mass folding quickly over the lap belt is quite reduced. Then, the amount of time it takes the torso to fully impact the shoulder straps is far greater too. KE is building, and the motion is more of a whiplash effect, making the layback position far more prone to high chest loads, similar to the neck tension scenario.

It makes perfect sense when you think about it in this fashion, and this is exactly the process I used to work this out.

gbaker

This is consistent with studies designed to examine head loads, among other things. Though not directly on subject, SAE paper 2000-01-3541 reported chest deflections in a F1 car, and there are others dealing with IRL and NASCAR seating configurations. Though we are not aware of a study designed to examine the specific issue of chest loads as a function of seat angle, Tom Gideon's statements are probably based on his familiarity with various test results.

It was initially believed that a more reclined seat would keep the head from hitting the wheel, but it was discovered that this configuration causes the body to first slide forward until the pelvis is finally halted by the lower belts. Only then does the torso begin to pivot up and engage the shoulder belts--a delay that does not occur with more upright seats. The result is two major differences in body positioning and loading: 1) the total head motion forward is much higher and, 2) the torso will necessarily have a higher velocity, which means the belt loads and chest deflection will be higher.

From the practical standpoint of most 'listers this is a trivial issue as the difference between a seat back of 20 degrees off of vertical vs. 30 degrees is small. The IRL seat back, which is 60 degrees off vertical, is another story.

Geo

Thanks Gregg. I think research studying seat angles could be most interesting. I just wasn't aware of any.

I can certainly see the issue in a formula type car where the driver would tend to attempt to squirt like a little sausage under the belts.

ronbo56

FWIW, I just drove a formula car for the first time (Skippy School) so I know exactly what RedlineMan means. The driving position - and belt loads - felt very different from what I was used to.

The school cars had a 5 pt. system, by the way, so even with the lap and shoulder straps tight I still was glad I already had my kids.