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Comment by bmitc | Hacker News Reader

Cars are risk adverse for a reason: people's lives are at stake.

steel is stronger than aluminum, in theory that should improve outcomes, all other variables held

Tesla vehicles also have some of the highest safety ratings around. Metal choice is also probably less of a factor than the shape of the pieces, so if they can do it with aluminum, steel is probably not that much different

edit...

It seems most vehicles are primarily made of iron and steel. So do these points made still hold up? Is your vehicle chassis made of aluminum or steel... the answer might surprise the commenters here

https://www.statista.com/statistics/882580/us-and-canadian-b...

That's not really how crumple zones and modern automotive safety works.

There are videos of old cars vs. new in crash safety tests. The old cars are "stronger" and hold their shape better, but that doesn't help the occupants at all. It only transfers more energy into the humans inside.

what prevents similar crumple zones with steel? You don't think we can apply the lessons learned from the last 50 years to a steel body vehicle today?

It's not like the strength needs to be consistent everywhere. For example, you might want stronger frame around the battery while still having a crumple zone. Again, I don't see the metal choice as a determinate factor here, you can always make a steel part that underperforms an aluminum one, vice versa too

Straight steel is tough AF, it doesn't crumple the way modern vehicle metal alloys do. Teslas do have those titanium frames that protect the major areas of the vehicle (passengers and battery mainly), but the rest of the car can be crushed to smithereens and you'd most likely survive.

Some parts of cars are steel, which is fine. But having the entire body of the vehicle be steel is where you lose any benefit. What's going to crumple when there are no crumple zones? Most likely your spine...

> What's going to crumple when there are no crumple zones?

So you posit that it is impossible to make crumple zones with steel? That we cannot design a steel part that has crumple features? (or in Tesla's case, a single cast rather than numerous parts bolted or welded together)

Mild steel is used in crumple zones. Stainless steel (like the Cybertruck) is not. Mild steel is much more malleable and provides a much better crumpling. As well as a whole lotta engineering behind the scenes to optimize the type of crumpling. Since stainless steel has chromium in it, it's much tougher when impacted. Which is great for being bulletproof, but is absolutely not the best choice when it comes to prioritizing passenger safety.

EDIT: this isn't me being some contrarian cuz I don't like Elon. This is thousands of scientists' discoveries, research, and data over the course of almost 100 years at the tops of their fields in material sciences. If stainless steel could make a good metal to ensure passenger safety, we'd be using it by now.

How about we wait for the actual safety tests before claiming it will be better or worse for passengers? I suspect Tesla will continue their industry leading safety ratings.

Tesla can't wish away physics and material sciences. Good luck!

The mechanical properties of steel are the reason why it's harder to make effective crumple zones. So yes, the material does matter a lot.

I can design both steel and aluminum parts that I can or cannot bend, there's far more to it than the raw material choice

harder does not mean impossible, any vehicle will have to go through the same safety review, and with Tesla's above average safety ratings, this all seems moot to me

Pretty sure we have more sophisticated materials science now, so we don't simply have to use such a heavy metal; better to use a lightweight alloy, with the usual crumble zones and strength from design integrity, not basic material strength.

Strength in vehicles has to do with directing force more than with deflecting it and for that to work you need to allow for deformation. A 'stronger' body by your definition may well be better at deflecting impact but it ends up being unsafe because a larger amount of the energy involved in the collision gets passed on to the interior of the car. Aluminum or steel isn't the question, the question is how does the chassis deform under various loads and impacts and what compromises do you have to make while engineering such a solution to achieve an acceptable outcome. The materials are different enough that you'd take a completely different approach for each, but you could still end up with a functional equivalent, and when all is said and done I'd expect the Aluminum version to be more expensive, a little bit lighter and harder (or even impossible) to repair after a collision.

Sure the car will come out less damaged, but the pedestrians will be far more likely to die.

Do you really think if a vehicle hits a pedestrian, that metal choice will make a difference? Wouldn't speed be a more important factor?

There are aluminum vehicles that weigh more, it's really momentum rather than gross weight

Body panel angles and speed are the big ones.

Or, to put it another way, can a soft body deform around the vehicle and be thrown away from the impact? The sharp wedge shape from the front grille to the hood kinda says "No" to me.

Regardless, it will be good to see what comes out of testing.

It's angle. But we'll see, European crash test are a lot less permissive than the US ones, as regulator don't think 'killing people in older cars, on bike or on foot is a feature!'. If it isn't sold in the EU, it isn't safe.

Once again today i'll be fair to Elon, most new US SUV/pickups don't pass EU crash tests.

>Tesla vehicles also have some of the highest safety ratings around.

According to the IIHS, the Model Y is the only Tesla that made the safest cars list out of nearly 50 vehicles.[1]

[1] https://www.consumerreports.org/cars/car-safety/the-safest-n...

Manufacturers learned decades ago that aluminum is safer for driving, more efficient, and easier to manufacture.

You say it like it's dumb to explore new designs because apparently we've already known for decades everything there is to know.

Stainless steel has been around longer than cars. I'd say it's fairly safe to assume that some R&D department has done exactly that. Their criteria was probably slightly different than Tesla's, but reduced costs (pennies matter when building things at scale) and increased safety (fewer fines, recalls, etc) are going to be the same.

The manufacturing process and design was entirely different though.

>The manufacturing process and design was entirely different though.

I used to work in automotive assembly, specifically in body panel stamping as a controls engineer (ie programming the robots). The big presses were set to accept both aluminum and steel. For example, the robots could use magnets for the steel or suction for the aluminum to move the parts, but the basic manufacturing used the same assembly lines. It was common to run both in the same shift.

> design was entirely different

Frankly, I have doubts. Being entirely different from the rest of the players in this multi-billion dollar industry is a pretty high bar to cross. Especially when some of them have been working in this industry (and had access to the same materials) for over a century.

Yet Tesla has tried different things and now we see the larger auto industry singing a new tune. The most visible example of this is the GigaCast. The Old Auto companies never thought this was a viable path until Tesla showed how superior it actually is.

https://www.youtube.com/watch?v=WNWYk4DdT_E

Sandy Munro is a leading expert in the auto industry, tears down all the vehicles and consults with all the major manufactures. He has many great videos on the trends. One thing he consistently points out is how adverse "old auto" is to new ideas or change of any kind, that they don't know how to innovate

Another example are the 4680 battery cells.

That is fascinating, thank you.

Steel bodied cars are not a new design.

We have learned a lot since they were common. Does our increased understanding over several decades factor in?

How does this logic hold up for another application, like the distributedness of the internet? It started out very distributed, but the last ~20 years we have seen a significant centralization. Yet we now see people trying really hard to re-decentralize major services. Should they not try based on your rationale, analogized?

We are not talking about any of that other stuff. It's irrelevant. We are talking about the Cybertruck, which Tesla has put into production and taken orders for. It is not an R&D prototype. So this is something very concrete.

Do you or Tesla have any data or studies or announcements that point to some unknown advancement with one of the oldest industrial materials in one of the oldest industries? This isn't some hypothetical discussion. You should have something to point to.

The fact of the matter is that there isn't a known advancement to point to. This is a production vehicle that goes against several well-known, established for decades design principles in car design. It will not absorb energy in a crash like every other modern car with crumple zones. It will deliver energy both to the crash target and to the inhabitants.

If Tesla had made some magic advancement, do you not think they would share it?

You keep implying towards some ethereal advancement and arguing with people based upon known, existing facts. Until there's something different, you're just speculating without basis and on a product made by a company well-known and infamous for lying and overhyping product features and advancements.

I'm not implying some ethereal advancement, rather that the commenters here are stuck in their opinions and ideas. People just want to hate on it, so it goes...

You keep implying it is impossible to build a crumple zone with a steel body, I just don't buy into the impossibility. Either way, despite orders and production, the vehicle will only be allowed on the roads of it meets safety standards. So either they will make it work or have to change things.

I'm sure you, as an expert, shall point out how I'm wrong yet again

The material is not new but the design very obviously is.

Please tell me which other car has a steel gigacasted frame.

Not if you plough your 10(?) tonnes vehicle into another one.

Unless you're on the other side of it

metal choice is such a small factor for crash outcomes... what if the other side is a semi truck?

Citation on that statement?

Materials matter a lot.

Speed(ing) seems to be the most determinate factor in crashes, which makes sense since it's half of the formula

https://www.demandthelimits.com/what-is-the-biggest-factor-i...

https://www.khanacademy.org/science/physics/linear-momentum/...

Also consider that existing vehicles are mostly steel today, this is just the body, which can be thinned out, as it does not serve as a major structural component

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