Your opinion please.

[John Herman]

Looks good to me.

[Z3_GoCar]

....
Option 2 utilizes "principle stress analysis" which was discovered by a German structural engineer named Otto Mohr in 1882. It is a proven mechanism for taking all the load data and resolving it to a single number. This is exactly the type of thing people are looking for (a single measure), but unless you are familiar with the technique it will sound like mumbo jumbo. Worse, from a business standpoint, the uninitiated may think we are making this stuff up just to make our product look good--and we do look good--when in fact it is a classic analysis tool.

Another option is to express the summary loads as percentage head load reduction. That still has problems, but at least it is less intimidating.

.....
[/b]

Mohr's theory states that the largest pricipal stress will be used to predict failure. I assume you're going to force normalize your graph to compress it down to one line. Also, for directional purposes I'd suppose you'd use the same directions used to define vehicle centered coordinates, i.e. x-left, y-fore, z-down and mx-pitch, my-roll, mz-yaw.

James

[gsbaker]

Mohr's theory states that the largest principal stress will be used to predict failure. I assume you're going to force normalize your graph to compress it down to one line. Also, for directional purposes I'd suppose you'd use the same directions used to define vehicle centered coordinates, i.e. x-left, y-fore, z-down and mx-pitch, my-roll, mz-yaw.

James
[/b]

X and Y axes are reversed in this convention. Like you, I initially assumed the opposite.

We will force normalize the graphs, yes. (I assume you are referring to resolving axial and shear loads to a value normal to the principle direction.) That's the question we are facing, i.e. different audiences may appreciate some but not all representations of performance, so we will probably layer the data somehow.

Personally, what I really want to get to is the point where we can compare the principal unit stress applied to the unit strength of bone, which is ~135MPa for a healthy 30-40 year old. This will tell us how close a particular design is to fracture for a given hit, and can be used as a basis for predicting the level of impact protection a design can offer--70Gs, 100Gs, 150Gs, etc. This is the kind of data people are looking for.

We probably won't publish this detailed level of data for some time. It relies on certain assumptions about the bone geometry and the mix between cortical and cancellous bone (different strengths) at the head-neck junction that needs to be confirmed. We'll take a SWAG at it in house (can't resist), but to publish it without verifying it helps no one.

At a minimum we will publish the raw load numbers.

[gsbaker]

Mohr's theory states that the largest principal stress will be used to predict failure.

...

James
[/b]

Jim,

Is this what you had in mind:


?

Titled for a bunch of biogeeks, these are the principal loads in the coronal plane. For normal people, that means the combined effect of neck tension, bending and shear in the up-down/left-right plane.

I know, I know, there should be no fixed plane associated with the true principal load, but we don't want to give away too much too soon.

Seriously, aside from titles, does anyone see any fundamental problem with this?

TIA

[leggwork]

Hi Gregg,
I'd suggest embedding some explanatory text right with the chart graphic. Then, when the inevitable out-of-context spread around the internet happens, there will be some hope that the viewer gets a sense of what the graphic is trying the show, the significance, etc.
cheers,
bruce

Jim,

Is this what you had in mind:


?

Titled for a bunch of biogeeks, these are the principal loads in the coronal plane. For normal people, that means the combined effect of neck tension, bending and shear in the up-down/left-right plane.

I know, I know, there should be no fixed plane associated with the true principal load, but we don't want to give away too much too soon.

Seriously, aside from titles, does anyone see any fundamental problem with this?

TIA
[/b]

[gsbaker]

Thanks Bruce. Good point.

There is much about this graph we don't like. It is fine for illustrating a point to a technical audience so there are no qualms about it's scientific merit. But we are very concerned that it may be misleading/misinterpreted. To do this properly one would calculate these loads for all planes and present the highest for each design. Unfortunately, we don't have that much data.

We will probably pull it from the Web but use it in the presentation

[gsbaker]

http://www.isaacdirect.com/html/Othe...estGraphs.html

This is very rough, but we promised you guys on the A-Team first look. We'll flesh it out with explanations and such, but until we do we will not link to it on our site and ask that you not spread this around--no real damage if you do, but we'd prefer not getting swamped with silly questions simply because someone doesn't get it.

Speaking of "getting it", we will probably trim this back significantly, or at least separate it into dummies, normal people and nerds categories. We'd greatly appreciate your input in that regard.

Without a summary measure you have to be pretty up on this subject to put these loads in perspective. As it is, what is shown is a subset of what was presented at SAE. Do yourself and SAE a favor and get a copy of the paper for a more complete understanding of these test procedures.

TIA

[leggwork]

why is there a difference in the test results at WSU vs. Delphi - I thought these were standardized test procedures?
cheers,
bruce

[gsbaker]

why is there a difference in the test results at WSU vs. Delphi - I thought these were standardized test procedures?
cheers,
bruce
[/b]

Slightly different. Same dummy, but the seats are different and the crash "pulse" (G load) is different.

[HONDA69]

Greg:

This one's from a "Normal Racer" who knows he should be wearing some sort of Head and Neck Restraint Device!! On those graphs presented with a red Line in them is the red line the probable Fatality line?? Based on info presented Baseline vs. multiple H&N restraint devices, something is better than nothing, but for my use data provides me with info to make informed judgement.

[gsbaker]

On those graphs presented with a red Line in them is the red line the probable Fatality line??[/b]

Close enough for decision purposes. The polite and official lingo is "IARV", which is an acronym for injury assessment XXX value (doing this from memory without references).

Both the ISAAC and HANS bump up against the IARV on some measures, which is why it is valuable to give consideration to a broad range of measures. Keep in mind that I've spent the last couple days watching crash videos that are nothing less than rolling explosions, so the idea that you might be injured at 70Gs with modern safety gear, when you would be toast at 30Gs without it, is good to know but we need to keep things in perspective.

Yes, pay attention to the red line.

[tom91ita]

greg,

thanks for all of your open and sharing attitude. in today's environment, this is quite rare, especially in safety equipment.

[gsbaker]

Thanks, Tom.

[gsbaker]

We did some slight editing of the presentation file and posted it here. Please right click and "Save as." ~6.5MB.

I think the videos are embedded in this file. Let me know if not and we will make other arrangements. You must see George White drive a Caddy into a wall at 60 mph. He broke his leg in two places.

Everyone have a safe weekend.

[greendot]

Hi Gary,
Let me also say thanks for being public with this and also for coming to the Waterford meeting with it Wed evening. I'm the guy who asked the "political" question.
I am not gettting videos to play in the downloaded presentation.
Also, I should have asked Wed, but just what is the White device?

Bruce Wentzel

[gsbaker]

Let me also say thanks for being public with this and also for coming to the Waterford meeting with it Wed evening. I'm the guy who asked the "political" question. [/b]

And with my answer went my credibility! That was a great group; thanks for putting up with me.

I am not gettting videos to play in the downloaded presentation. [/b]

I was afraid of that. Apparently videos are linked to those files, not contained within. I'll get it fixed.

Also, I should have asked Wed, but just what is the White device?[/b]

Remember the video of the guy crashing the Caddy into the wall? That was George "It freakin' works!" White, and you can buy an updated version in Kevlar from his operation for ~$400.

[itracer]

I think the videos are embedded in this file. Let me know if not and we will make other arrangements. [/b]

Try saving it as a Power Point show. (.pps) Then the movie should stay embedded.

~Jason

[greendot]

And with my answer went my credibility! That was a great group; thanks for putting up with me.
I was afraid of that. Apparently videos are linked to those files, not contained within. I'll get it fixed.
Remember the video of the guy crashing the Caddy into the wall? That was George "It freakin' works!" White, and you can buy an updated version in Kevlar from his operation for ~$400.
[/b]

You were paying attention.

I assumed the White was the same, but never saw the "nuts and bolts" of the system. Guess I'll do the research just to satisfy my curiosity.

BTW, here's a link that was posted to the Waterford site that bears on the topic:
http://news.bbc.co.uk/1/hi/england/h...re/6217036.stm

[gsbaker]

Try the bottom of this page.

I'm nearly positive you have to link videos to PPT files, so those links will have to be reconstructed after everything is moved to your machine--or just watch them independently.

You were paying attention. [/b]

It's a rare moment.

I assumed the White was the same, but never saw the "nuts and bolts" of the system. Guess I'll do the research just to satisfy my curiosity.[/b]

George is here.

BTW, here's a link that was posted to the Waterford site that bears on the topic:
http://news.bbc.co.uk/1/hi/england/h...re/6217036.stm
[/b]

That's amazing. Just enough force to break the bone, but not enough for soft tissue damage. That's as close as you can cut it. Wow.

[gsbaker]

Try saving it as a Power Point show. (.pps) Then the movie should stay embedded.

~Jason
[/b]

Aha! That may be the answer. Thanks for the tip!