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Comment by Animats | Hacker News Reader

Nice, but no more body and frame repairs. One dent to those big parts and it's time for a new car.

The outer body of the car is still sheet metal and can be repaired as before, if not easier. The cast parts are only on the inside and also traditional cars are usuall a write-off, if the internal frame is damaged. The cast parts might even be stiffer and hence more difficult to damage.

Tesla for sure has thought about this. For example, the rear cast has struts which hold the rear bumper and consequently are likely to be damaged during an accident. But these struts are designed to be cut off and replaced with new parts.

> The cast parts might even be stiffer and hence more difficult to damage.

Someone with more experience should step in and correct me but my understanding is that this is how we used to do things and stopped because it turns your passengers into soup. You need those parts to crumple. I'm sure Tesla has thought of that and wouldn't downgrade the structural safety but it does mean the new design is probably just as easy to damage but more expensive to replace than traditional designs.

Cars are designed with a strong central structure (passenger cell) and weak areas at the periphery (crumple zones). These cast parts are in the "strong" area, I think.

I suppose you want the crumble zone to be on the outside. Outside critical parts and easily replaceable. Then you want the inner shell not to disform, or not too much, as otherwise you are sending metal into body parts.

The crumple zones are unaffected by the casts and the casts can crumble as well. But if the car gets deformed beyond a certain point, it would be totalled anyway. If you look at pictures of the casts, the front ones mount the wheels but end there, the rest of the car ahead of them is made from sheet metal and metal bar with the purpose of crumbling easily.

A steel unibody may bend in a moderate collision, but it can often be straigtened by a competent body shop. Castings are more brittle, they tend to crack, not bend. And they can't really be welded back together. I think having major parts of the frame as cast pieces will reduce repairability, but time will tell.

As far as I remember from my material sciences classes, casting is a lot more difficult to model and QC than stamped and welded/glued steel panels. This is also a completely new process for automotive at this scale which complicates it further.

I am sure they hired the best engineers and tested as best as they can, but this seems so new that I expect there to be a lot of problems with the first year or two of production -- maybe a reason why this process is coming to North America last. And given how castings usually fail, I don't expect failures to happen immediately, but after 3-5 years or more.

But then again, I'd have said the same about using "laptop batteries" for electric cars.

> maybe a reason why this process is coming to North America last.

Fyi, the article says it's coming to Gigafactory Berlin and Gigafactory Texas first. It's only coming to Gigafactory Freemont last.

Doesn't the Y from Fremont already have the rear casting, as of January 2021?

> This is also a completely new process for automotive at this scale which complicates it further.

The Trabant had supply limitations throughout its entire production run due to scaling issues casting Its duraplast body.

The model Y, as delivered today, already has a very large casting in the rear: There are many sources out there describing it, and how it simplifies model Y assembly compared to the otherwise rather similar model 3. What they are describing here is to go further with a process they are already doing very advanced work on in production cars. They might have problems. They can fail altogether. Maybe it turns out to be a bad idea anyway, but I do not expect Tesla engineering to be just naive at this.

As for why Fremont is the last place to get the changes, it seems to me that there are simpler reasons: That factory is the main source for Teslas on the road today, and it operates more or less at capacity. Adding a new process would slow it down, at least temporarily. The Berlin and Texas factories, AFAIK, have yet to start operation, so they are good places to try something new, given that Tesla is selling the cars about as fast as they can make them. This is how a lot of the industry does things: Make your new facilities have the latest and greatest, and only retrofit the old ones when it makes economic sense to dismantle the older process. No matter what the theoretical savings might be for a new casting vs so much soldering and assembly, the old process is making cars, today, so decommissioning it is not as good a value proposition as just not even trying the old process in a new facility.

As long as insurance premiums stay reasonable, it’s a win for manufacturing speed and complexity, product quality, as well as the salvage market. And in my personal experience, vehicles are never quite the same after frame damage repairs.

(legacy [Aug 2021 build, hah] Y owner)

> And in my personal experience, vehicles are never quite the same after frame damage repairs.

Same, a car with a damaged and repaired frame is usually a different car than the original. Overall this is a win.

Fwiw this isn't the first mass-produced consumer vehicle with a unibody construction. For one example, the Nissan Pathfinder had it back in the 90s, though later returned to ladder-on-frame.

https://en.wikipedia.org/wiki/Nissan_Pathfinder#Second_gener...

> this isn't the first mass-produced consumer vehicle with a unibody construction

Isn't it already unibody construction, along with basically every other non-truck vehicle in production (and some trucks, too)? The only thing new is using casting for so much of the structure.

The unibody construction isn’t unique at all in 2022. Virtually every car on the road (except for handful of pickup and some SUV/off-roader models) has been built this way for decades now, and isn’t what’s exciting about this new approach from Tesla.

What’s unique is that so much of the unibody is just 2 castings - previously the front and rear required joining 140 separate parts. Such a massive front and rear casting has never been attempted in car production, the mechanical press used to do so is a record size for a car company.

VW’s ceo Herbert deiss has stated this is a massive innovation from Tesla that ultimately will enormously reduce time to assemble a vehicle - we don’t need to just take elons word for it. Time to assemble is everything when it comes to car profits. Herbert points out a VW ID3 takes ~3 days to finish assembly, with this process Tesla should be able to complete a model Y in just 10 hours, putting large competitive pressure on VW too. VW’s margins on their electric stuff hasn’t been that great to begin with either.

They will be designing the cars with buffers, but if a crash can go through all of that AND damages the single casting chassis, which are a lot stronger, then you should thankful because you'll likely have gotten way more injured with a traditional chassis.

Damage in a collision is a good thing as it requires energy. Not sure why you say a stronger part will reduce injuries.

Perhaps because the stronger part takes more energy to damage and thus absorbs more?

Absorbs? What does it do with that energy, then? Radiate it? AFAIK it's just stiffer so it will effectively transmit the energy along to the next part in the chain. Eventually, that'll be a human.

I meant the energy will be used to deform the chassis, but perhaps I am over my skis here.

Into heat mostly. It takes quite a bit of energy to deform a lump of metal. You need that energy for force atoms past each other, and the metal gets hot in the process.

So yes, absorbs the energy, then radiates it as heat.

The point that's being made is-- if there's a certain amount of energy being dissipated in a collision, it's better for things to crumple so that the energy is dissipated over a long time period and the peak accelerations (which damage occupants) are less.

A hypothetical perfectly rigid car that stops instantly in a collision instead of deforming is not safer for the occupants, because suddenly they will be going 40MPH inside a not-moving car.

Because they’re saying these cast are the inner shell that forms the passenger compartment. If they’re deforming, then they’re deforming into the space where the passengers are, and humans squish much easier that aluminium castings.

Regardless if it’s a unibody or a welded chassis parts of it would be designed to give under stress and parts of it would be designed to hold to protect the driver.

In a bad accident with any BEV i would be far more worried about the battery being compromised than the chassis tho.

Hopefully these huge casts can be recycled and recast. If so, they don’t seem terribly wasteful. I’d also hope that minor repair of the cast part is possible for the smallest dents. I’m not an expert in this area.

Metal is extremely recyclable

Especially aluminum which I believe is what Model 3 and Ys are made out of

No, you're thinking of the Model S. The 3 and Y are predominantly steel.

Ah, I have it backwards.

The large chassis castings in the Model Y, however, are an aluminum alloy.

I wonder if having less structural adhesive between metal components makes it more easily recyclable.

We'll see how things pan out, but this might actually make repairs a better experience over time - fewer types of parts means it's easier to keep them in stock, and likely less time required per replacement.

Tesla can't keep parts in stock because they're desperate to prioritize production over parts inventory, not because they have too many parts.

This will be a nightmare. A damaged fender now means instead of a fender-sized package that easily fits in a truck with lots of other things, you now have a massive half-a-car sized package.

This also doesn't bode well for parts availability in the future. I can't see Tesla switching these massive presses back to producing older designs of panels.

Why would a fender replacement require this? The castings are for the chassis, not the body.

I don't think so. I think it will mean more write offs. These castings replace current pressed panels, so anything in that area will now mean a new body shell -which realistically will mean a written off vehicle - where repairs would currently be an option.

I think this is manufacturing optimisation at the cost of overall life optimisation, like the epoxy-encased batteries which are less recyclable than the previous generation.

Other commenters have pointed it out in different threads, but these castings won't replace the panels. They will replace the current chassis.

I'm aware of that. But using those terms is somewhat misleading - modern vehicles use a monocoque chassis, and these castings will be in areas which are routinely damaged in collisions where panels can currently be replaced/repaired by any competent bodyshop. You can usually buy such sections individually, unpick the originals and replace with new ones, returning the vehicle to as-new condition - even when you're a DIY mechanic with suitable equipment.

That won't be the case with castings, and even less so with Tesla given their approach to third-party repairs.

I really doubt that replacing one of these cast parts is feasible -- everything is attached to them, you'd have to take apart and rebuild almost the whole car.

Aren't body and frame repairs for Teslas already pretty bad? I've looked at the insurance rates for used Model S and they're massive.

I pay less than $100/month in insurance for a 3 year old Model S. Our Model Y is about $130/month. Sunbelt state, top tier insurance company.

I pay about 900€/year for my Mercedes and a Model S would've been something ridiculous like 1800€/year.

I presume that you are also in Germany as well. The insurance rates here are straight up highway robbery. I wanted to get a Tesla, but the insurance quoted me more than 2000 euros.

Nah, Finland. But I guess there's some consistency in Tesla insurance rates being higher than other cars, so I guess that they're more prone to get into crashes, and/or they're massively expensive to repair.

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