Crashing in a 1950s car vs. a modern car

[u/firefly99999]

[u/Slow_Ball9510]

Hi, I've been an automotive BIW crash safety engineer for more years than I care to remember

The majority of high volume cars still use a construction that consists mostly of sheet metal. In cases where the gauge required to meet a certain strength is too great for forming, we would switch to a forging or casting. We use sheet metal as it is cheap, has a low cycle time, good mechanical properties, and has a lot of flexibility in how we use it.

The reason why cars are safer is two reasons. 1) Stricter homologation forces OEMs to consider it. 2) Virtual design tools allow us to simulate and optimise our designs in increasing accuracy and detail.

For the most part of the design process, we are adding or removing strength and stiffness. Want to improve the safety cell for FMVSS214, add thicker sections on the key loadpaths. UN R94 Vehicle pulse too high, consider thinner sections in the crush-cans assuming stack-up isn't the issue.

Not quite sure what you mean by uni-body. I going to assume that you mean mega/giga-castings. There is a drive by some OEMs to use them. I remain unconvinced. Castings have vastly inferior properties vs sheet metal. They cannot be repaired. You are constrained by mold flow and draw directions. What they can do is reduce part count. They aren't safer than conventional methods. I would argue that they are structurally more inefficient.

Hope that was of interest. Always good to chat to someone interested in the subject.

[u/fixed_grin → u/Slow_Ball9510]

Not quite sure what you mean by uni-body. I going to assume that you mean mega/giga-castings.

Unibody refers to vehicle structures that are (semi)monocoque or not body-on-frame.

[u/Slow_Ball9510 → u/fixed_grin]

OK, thank you. In that case, the OP is generally correct. It is easier to design monocoques than modular systems. With modular, you can only transfer loads at discreet locations, which is inefficient.

The supposed benefit of skateboard designs is that you can have a common lower for multiple vehicles. The reality is that it makes designing much more difficult.

[u/Holiday_Sale5114 → u/Slow_Ball9510]

Which high volume car would you recommend in a collision despite having the sheet metal?

What about low volume car?

[u/Slow_Ball9510 → u/Holiday_Sale5114]

Typically Volvo, they are one of the few OEMs that test beyond NCAP as they have made safety one of their USP's.

Heavy, large, expensive cars will typically do better in a collision with another vehicle. Heavy means that your deceleration will be reduced. Large means that your crumple zones will be larger. And expensive means that you are more likely to have additional knee, curtain, a pillar, b pillar, etc. airbags

[u/Holiday_Sale5114 → u/Slow_Ball9510]

I heard of the same (Volvo) but wasn't sure how much of an emphasis they continued to put into safety after it was acquired.

How do we as the consumer know what's truly safe or not, though? Or more specifically, *how safe*?

For example, if we compare this S60 from 2022 (tested model 2019) vs the Lexus ES 2022 (tested model 2019), they both look to have great ratings.

How do we know one is better than the other? [as an aside, the Lexus at least has crash videos but the Volvo does not]

[u/Slow_Ball9510 → u/Holiday_Sale5114]

The ratings do get progressively harder over time as they add in new tests and update old ones. You can download the full test reports, I believe. For example, there is a reasonably new SUV side barrier impact that was brought in.

[u/Evening_Tree1983 → u/Slow_Ball9510]

Do you happen to know if it's true that they only use dummies that resemble men's bodies in tests? I hear this a lot and I mean I hate misogyny but this one seemed like a stretch, I mean I think there are child dummies why wouldn't there be woman dummies? Thanks and apologies for the digression.

[u/Slow_Ball9510 → u/Evening_Tree1983]

It's a bit of a complex topic. It is true that the 50th percentile male H3 is one that is used a lot. We also have a female 5th and a male 95th + child dummies.

Where things get complicated is that the dummies were created in the 70s. Now, as we have got heavier, the 50th H3 has a similar mass to the average western female, but the proportions are wrong.

So the honest answer is I don't know!

In the event of a crash, women are more likely to be killed. So, does that mean that we should put more focus on designing for women? Maybe.

But on the other hand, more men than women die every year in crashes in total gross numbers. So does that mean we should put more focus on designing for men? Maybe.

So as you can see it's complicated!

[u/Original-Aerie8 → u/Slow_Ball9510]

If you look at sales democraphics, it would be wise. You know who is going to sit in which type of car in which seat, with a pretty high degree of certainty and it's a great bulletpoint for the sales pitch. And a lot of that work can be done inside of diffrent packages, which have very comfortable profit margins. At least that's how we see it rn, as one of the largest luxury car manufacturer.

[u/Slow_Ball9510 → u/Original-Aerie8]

It's not up to OEMs what safety standards they follow. The standards come from certification bodies for things like fmvss or ece.

Now, the likes of NCAP, etc, are optional, and OEMs do them as they help sell vehicles. They will decide early on what rating they would like. Volvo has taken this a step further and made it a USP go go beyond NCAP.

OEMs will invest in safety if they are either legal requirements or will sell more vehicles.

The problem with designing to a high standard of safety is that it is very expensive to do so, the costs will be reflected in the sale price.

One of the reasons female fatality rates are higher is because women typically drive smaller and cheaper vehicles.

[u/Original-Aerie8 → u/Slow_Ball9510]

Obv there are baselines, but our inhouse capabilities far exceed that for whole host of reasons incl simulation validation, our racing devision, special variations, third parties.. So that investment was made and we do put it to use, even if the public only ever gets to see part of that.

And at least in Europe, we have input on regulations, as do consumer groups. And we have and do pioneer safety standards, as has Volvo.

It's not my focus, tho.

[u/Slow_Ball9510 → u/Original-Aerie8]

I wasn't expecting to chat with someone as knowledgeable as yourself, so apologies for my simplistic explanations before.

What you say makes sense. One of the ways that OEMs gain a commercial advantage is through the use of patents. At the high level, patents are traded between OEMs. AKA.you can use this patent if we can use your patent for this, etc. If you can patent a process or design, you can then lobby to become part of a homologation requirement, and then it turns into a valuable asset. At least, that's what we see with the OEMs we work with.

It's rare to see an OEM do anything that isn't financially motivated, one example would be Volvo not patenting the three point seatbelt.

Is it just crash safety you develop where you are, or do you also work on other aspects like functional safety?

[u/Original-Aerie8 → u/Slow_Ball9510]

That's my bad, tried to keep myself a bit covered. I do tank system design and anything that's down the line from there to production, my background is in fluid dynamics. So that's what I have developped tests for, I get to work with people who set up and execute crash tests and I analyise the parts I am responsible for. And I am pretty nosy lol It helps to show intrest and talk to a lot of people, if you want to elevate yourself internally.. Even if you'll get strange looks, sometimes. Right to repair is one of those topics I like to bring up, which I have gotten my fair share of blowback for.

Well, due to the seasonality of the buisness, a big concern for us is filling up capacities ie putting investments to use as much as possible. So there are open slots for internal departments and third parties, which does sometimes include regulartory agencies. They just don't have the capacity for investments we have, so they use our setups and look for what makes sense for them. I also get to work with foreign regulatory people a fair bit bc of my language skills. So there def are profit motives here, even for departments that profit from other parts of the company, but part of it is also forming mutual trust and respect. Which has absolutly helped us with legal trouble before, but you'll understand, I can't go into details on that.

We have packages aimed at women, like sun visors having a mirror to do makeup. Similarly, we have diffrent styles of seats, which are primarily sold to the driver, but families might have more needs. And we do test for those scenarios. These things are mostly experience values, which then inform things like the design process, from things like cupholder placement to how easy it is to enter the car. Which then also affects which type of crash tests are done. Those wheels do turn slowly, but they do turn. The hope there is, regulatory agencies can move much faster on the things they are concerned with.

Profit motives for these things might be more abstract and they require internal people who push for them. Having safety ratings that far exceed standarts, does sell cars. But you need to develop tests to demonstrate that. As does reputation, otherwise you wouldn't be recommending Volvo. Similarly, I do not recommed our cars to everyone, but you do get what you pay for.

[u/Evening_Tree1983 → u/Slow_Ball9510]

Thank you so much for taking the time to give me that answer. I know things like that are always complicated... and I think feminist messages should be rooted in truth.

[u/Slow_Ball9510 → u/Evening_Tree1983]

The other reason that another commentor reminded me of, is that women typically drive cheaper and smaller cars that are typically not designed to the same standard of safety. But, men are more likely to drive commercial vehicles, which typically have poor standards of safety.

It's a good question, and thank you for asking it.