Your opinion please.

G

gsbaker

New member
If you could review crash test data for nine head and neck restraints, coming from 21 crash tests and generating over 200 load measures, which format would you prefer:

1. Individual charts for each load measure comparing side-by-side results for each product (we're talking ~15 charts),

2. A summary universal load analysis which distills all loads to a single value, but which is not intuitively obvious, i.e. second year engineering school, or

3. Both.

TIA
 
As much as it might be a pain, I think you'd have to do both.

There are some folks who will just buy based on a recommendation from a trusted friend.
There are some folks who will want to read everything they can, but may not be able to interpret the second-year-engineering charts.
There are some folks who ARE engineers, and will want those charts.

It's only more work and money to produce both, right? :D

Personally, not seeing it I don't know if I could interpret option 2 properly or not.....so, I'd want the option of both just in case.

Jarrod
 
It's only more work and money to produce both, right? :D [/b]
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In this case no. We are putting together all (option 3) of this stuff anyway for an SAE presentation next week, so there is no incremental effort.

Personally, not seeing it I don't know if I could interpret option 2 properly or not.....so, I'd want the option of both just in case.

Jarrod
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Makes sense Jarrod. Thanks.

To expand a bit, Option 1 presents such load measures as axial force, shear and bending about all three axes (X, Y & Z) for every product tested at both Wayne State and Delphi. That's the "choke a horse" part. This is very straight forward data but may leave drivers asking what it all means, only because there is so much of it.

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.

We should probably throw it all out there and adjust as needed.
 
first of all, i appreciate you discussing this in public. that, imho, says a lot of you and your confidence.

i think it was discussed before, but i prefer that the powers that be at nasa or scca make the requirements for H & N restraints be something like x% reduction using sled test methods ABC and not make it to an SFI.

any company that can meet this should be approved. i can respect people's choices for the HANS, Isaac, R-3, etc.

i am one of the ones waiting on the side lines (i think we are relatively numerous since the last events i was at, the majority had horse collars or nothing) to buy something because i am not sure that my ~$1000 investment will be formally approved and the $#%@ rules always look like there will be something announced in the next couple of months.

i think i have been waiting a couple of months for a couple of years.
 
It depends upon your target audience. Remember, it's very easy to lose 'em up front with to much information, rather than piquing their interest with not enough.

I would suggest that a stepped approach is in order - start with a broad overview, and depending upon audience reaction and need, be prepared to delve into the minutia. Keep it simple, and avoid mind-numbing graphs with a zillion colours. It may look good to you, but to the guy sitting in the 23rd row it's a blur, and he or she will dose off.
 
Distilling the info into one number is tempting, but it's highly political and suspicious as well.

If YOU do it, the uninitiated will suspect you've chosen to give more value to your stong suits, and have "cooked the books", so to speak.

If an organization does it, there is still some suspicion that the organization did the same thing, but for other reasons.

I'd say that to the average person, if an organization did it it would bear more weight than if an individual company did it.

Then we have people who are critical thinkers.

They want numbers and math.

So, my answer is both, and show and explain the math for the idiots like me...LOL
 
To expand a bit, Option 1 presents such load measures as axial force, shear and bending about all three axes (X, Y & Z) for every product tested at both Wayne State and Delphi. That's the "choke a horse" part. This is very straight forward data but may leave drivers asking what it all means, only because there is so much of it.

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]
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I am assuming, maybe wrongly, that you will include an unrestrained load measurement as well. It seems to me that if I know how much of a reduction is made by device "A" in axis X,Y, or Z and then compare that to the corresponding data of device "B" I could then start to evaluate the effectiveness of the particular device. In other words, device "A" might reduce 2 of the three loads substantially but the third could be off the charts.

Summary loads appeals to me for a quick look, but the real meat of the issue is in the data and the comparisons across the options. The hard part will be making the data representation simple enough for a casual user, not the SAE engineering types.

Just another $.02 worth form someone else who is waiting to make a purchase. I really do appreciate your being up front about the issue and opening yourself up to criticism. Thanks.

Paul
 
Then we have people who are critical thinkers.

They want numbers and math.

So, my answer is both, and show and explain the math for the idiots like me...LOL
[/b]
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Hey Jake -

Do you work in sales? :wacko:

I always have trouble explaining math using monosyllabic words. :P
 
I am assuming, maybe wrongly, that you will include an unrestrained load measurement as well.[/b]
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Yes, there will be "baseline" data for all tests, i.e. a dummy with a helmet but no restraint, and is always listed as the first value on each chart.

It seems to me that if I know how much of a reduction is made by device "A" in axis X,Y, or Z and then compare that to the corresponding data of device "B" I could then start to evaluate the effectiveness of the particular device. In other words, device "A" might reduce 2 of the three loads substantially but the third could be off the charts.[/b]
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Bingo. That's the entire purpose of the exercise. Here's an example of how different designs yield different strengths and weaknesses.

Good tension numbers for a certain group of designs:

Chart1.GIF


...and HANS rules the roost in frontal shear:

Chart3.GIF


The hard part will be making the data representation simple enough for a casual user, not the SAE engineering types.[/b]
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Agreed, and with nearly 20 charts it becomes a challenge.

I really do appreciate your being up front about the issue and opening yourself up to criticism. Thanks.

Paul
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Anytime. The adults know that there is no such thing as a perfect product, and that all have strengths and weaknesses. We look pretty good when you add everything up, so we'll just leave it there.
 
i think i have a good idea that "z" is the vertical load or tension on the neck since "z" is elevation for other equations i use frequently (ChE). but just for the record, what is considered to be "x" and "y" in a car? is "x" forward motion and "y" lateral?

cause to the first users of grids in algebra, "x" is usually laid out on the paper for left to right, "y" is vertical and "z" goes into the paper and some have construed that to be forward or behind, etc.

also, the threshold of injury for a typical hard hit of 50 g's, etc. would be nice. i was quite impressed with the numbers on your website and i think a line for injury threshold would be a good way to illustrate what is above and below (essentially, inadequate and adequate), etc. would be nice and quick and most of all, intuitive.

and will there be any three dimensional graphs? cause in any crash video i have seen, the neck is going in all three directions at once and i am assuming that the resultant vector/force (i hope that makes sense cause it has been way too long since i had to use or listen to these kind of words!) is part of what has to be considered.
 
i think i have a good idea that "z" is the vertical load or tension on the neck since "z" is elevation for other equations i use frequently (ChE). but just for the record, what is considered to be "x" and "y" in a car? is "x" forward motion and "y" lateral?

cause to the first users of grids in algebra, "x" is usually laid out on the paper for left to right, "y" is vertical and "z" goes into the paper and some have construed that to be forward or behind, etc.[/b]
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Yes, Z is vertical. The X axis is front-to-rear (from the dummy's perspective) and Y is left-to-right.

also, the threshold of injury for a typical hard hit of 50 g's, etc. would be nice. i was quite impressed with the numbers on your website and i think a line for injury threshold would be a good way to illustrate what is above and below (essentially, inadequate and adequate), etc. would be nice and quick and most of all, intuitive.[/b]
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That's a good point. Unfortunately, threshold limits are not available for all measures, but we could include them where available.

and will there be any three dimensional graphs? cause in any crash video i have seen, the neck is going in all three directions at once and i am assuming that the resultant vector/force (i hope that makes sense cause it has been way too long since i had to use or listen to these kind of words!) is part of what has to be considered.
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This is the appeal of a summary measure. Given the bone geometry one can determine the unit stress and relate it directly to the bone strength. In other words, the net effect of all these loads acting simultaneously can be analyzed to be either above or below the fracture threshold. This would not require a 3D graph--although one could be used.

I think we will be keep it rather simple, with references to more detail as some sort of appendix.

Thanks all.
 
For clarity, a simple diagram showing the x,y,z directions and also the the direction of the forces you are referencing. I invision a simple drawing of a head/neck/shoulders, a simple axis system imposed on it, and then the arrows showing the forces. For the engineering types, terms such as shear and axial make sense, but for the non-engineer, I imagine a picture with arrows (and maybe some very simple text) would be easier to visualize. For example, an axial force occurs when lifting someone by their head, a shear force occurs when the vertebrae of the neck want to slide across the top of each other. Then, given the mechanics of the basil (sp?) injuries, is there one or more of these forces which is considered more critical?
 
For clarity, a simple diagram showing the x,y,z directions and also the the direction of the forces you are referencing. I invision a simple drawing of a head/neck/shoulders, a simple axis system imposed on it, and then the arrows showing the forces. For the engineering types, terms such as shear and axial make sense, but for the non-engineer, I imagine a picture with arrows (and maybe some very simple text) would be easier to visualize. For example, an axial force occurs when lifting someone by their head, a shear force occurs when the vertebrae of the neck want to slide across the top of each other.[/b]
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Something like this should work (at higher res, of course):
<div align="center">
SignConventionSmall.jpg
</div>

Then, given the mechanics of the basil (sp?) injuries, is there one or more of these forces which is considered more critical?
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Yes, which complicates things further. We are not doing anyone any favors if they infer that all loads are equally dangerous.

Fz is the most important. It is the first value people want to see.
 
The above image is helpful, but would be more helpful if it listed Fz, Fx, etc.

How I wish I was travelling to the SAE show to see this presentation (and, more importantly, some of the crowd reactions!). :happy204:
 
Others have already expressed my preference, but I will add my vote. Show us the numbers!!! Then tellus what they mean. My right brain is really fighting with my left brain. Pictures go a long way in describing the forces that are being measured, numbers allow me to evaluate options. Having a BS in Computer Technolgy (a form of engineering), I can appreciate the composite number you talk about and agree that it too would be useful as long as it is explained in terms that everone can understand and realize what it means.

Great work! Good luck with the presentation!
 
Show us the numbers!!![/b]
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Not yet, Bill! We've assigned the copyrights to the paper to SAE International. They cover their costs and provide peer-reviewed screening by selling copies, so we don't want to steal their thunder before it is published in the next few days. It is data we collected from various sources, however, so we have every right to present it in our own format eventually. We support SAE's work so we don't want to do anything that would hinder their efforts.
 
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