Does Cybertruck need mega-castings too?

[firsttruck]

Factory making Cybertruck does not need a paint shop

The Berlin factory Model Y will have front and back mega-castings.

But what about Cybertruck, does Cybertruck need mega-castings too?

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[Luke42]

Factory making Cybertruck does not need a paint shop

The Berlin factory Model Y will have front and back mega-castings.

But what about Cybertruck, does Cybertruck need mega-castings too?

I've wondered this too.

My guess is "yes", because I couldn't figure out how the exoskeleton was reinforced against side-to-side sheer forces. A big casting right about where the cab and the bed meet would answer a lot of questions I have.

Even if my questions are wrong, stainless steel castings seem like a reasonable thing and I can imagine them being useful in several places in the structure.

But, then again, I get electronics made, so what do I know?

 

[hobbit11]

Factory making Cybertruck does not need a paint shop

The Berlin factory Model Y will have front and back mega-castings.

But what about Cybertruck, does Cybertruck need mega-castings too?

great question.

 

[EVCanuck]

A big casting right about where the cab and the bed meet would answer a lot of questions I have.

Even if my questions are wrong, stainless steel castings seem like a reasonable thing and I can imagine them being useful in several places in the structure.

I might be wrong as well but I don't see how Tesla or anyone else can make SS castings. If they make castings for the CT it will be of the same aluminium allow they developed for the Model Y. But I believe they would need a welded steel structure for CT underbody.

 

[Crissa]

The answer is 'sure'.

While the structure is folded steel, you still need stuff to hang the batteries from, firewalls around the cab, the rig to hang the wheels and motors from. Aluminum used that way is very stiff, and fills the gaps.

-Crissa

PS, there is no 'connect bed to cab' since the bed and the cab both hang as one, the deck of a bridge cradled in the arms of the exoskeleton sides.

 

[Luke42]

I might be wrong as well but I don't see how Tesla or anyone else can make SS castings. If they make castings for the CT it will be of the same aluminium allow they developed for the Model Y. But I believe they would need a welded steel structure for CT underbody.

Stainless steel can be cast:

Using the same material avoids bimetallic corrosion, and makes it much easier (possible?) to weld together.

Many vehicles use a combination of steel and aluminum, so using both is definitely possible. There are definitely engineering tradeoffs to be considered.

However, I'm not an expert in those tradeoffs, so I'll merely assert that it is possible to cast stainless steel, and that there are tradeoffs to using aluminum castings, and that there questions here that could be better answered by someone else.

 

[firsttruck]

The answer is 'sure'.

While the structure is folded steel, you still need stuff to hang the batteries from, firewalls around the cab, the rig to hang the wheels and motors from. Aluminum used that way is very stiff, and fills the gaps.

-Crissa

The heavy Cybertruck is supposed to be rated to handle huge payloads, huge towing, heavy duty off-roading at high speed and maybe even Baja.

Am I wrong to think that normal highway car (model Y) mega-casting would be too weak and even making extra thick casting might be difficult (model Y mega-casting is already the largest in the world)?

Will standard aluminum mega-casting be tough enough?

I kind of though the underbody would need to be welded stainless steel too.

 

[Crissa]

The heavy Cybertruck...

...You use aluminum so you can save that weight for things you need, like the batteries and skeleton.

Yes, they described the exoskeleton as folded and welded.

But there are lots of parts you need, but don't need the strength and certainly not the weight of steel - many of the interior parts. You don't want a steel panel for the firewalls, because you don't want the weight or strength there, you need 'nonflammable'. You don't want steel for battery cables or electrical housings because that's just extra weight. Plastics and aluminum and laminate castings are better for that. Lots of these places need bulk not thin strength, so that's where the aluminum will go. Or needs heat conducting properties. Steel does that poorly!

Save the weight for the exoskeleton.

A steel pipe is strong, a steel bar is strong... but for the weight over a span, a steel pipe filled with aluminum would be stronger.

-Crissa

 

[firsttruck]

...You use aluminum so you can save that weight for things you need, like the batteries and skeleton.

Yes, they described the exoskeleton as folded and welded.

But there are lots of parts you need, but don't need the strength and certainly not the weight of steel - many of the interior parts. You don't want a steel panel for the firewalls, because you don't want the weight or strength there, you need 'nonflammable'. You don't want steel for battery cables or electrical housings because that's just extra weight. Plastics and aluminum and laminate castings are better for that. Lots of these places need bulk not thin strength, so that's where the aluminum will go. Or needs heat conducting properties. Steel does that poorly!

Save the weight for the exoskeleton.

A steel pipe is strong, a steel bar is strong... but for the weight over a span, a steel pipe filled with aluminum would be stronger.

-Crissa

Yes, the interior shell and many components could be aluminum or light steel.

But the Cybertruck is going to be much heavier and a Model-Y and has much higher loading (payload/two) than the Y and be used in much higher force conditions (off-roading) than the Y.

The model Y is primarily designed for the forces from on-road travel with mostly passengers (little other payload). The standard Model Y mega-casting has mounting points for shocks and the entire suspension where the forces will be transferred to the body of the car.

In the Cybertruck those suspension points might have order of magnitude more force applied.

 

[EVCanuck]

Stainless steel can be cast:

Using the same material makes avoids bimetallic corrosion, and makes it much easier (possible?) to weld together.

Many vehicles use a combination of steel and aluminum, so using both is definitely possible. There are definitely engineering tradeoffs to be considered.

However, I'm not an expert in those tradeoffs, so I'll merely assert that it is possible to cast stainless steel, and that there are tradeoffs to using aluminum castings, and that there questions here that could be better answered by someone else.

I should have specified that die casting SS is currently not possible, although Tesla could build a giant ceramic die but that thing will break/crack after a dozen of cycles. Anyway I still don't see Tesla using SS for anything else than CT's skin, which is huge SS quantity by itself. Stainless steel has at least 8% Nickel content and Elon's already got a headache sourcing the Nickel for the batteries.

 

[Crissa]

Yes, they'd definitely use it in different places than the Y.

But putting aluminum up against stainless is a great combination - steel is hard and strong while aluminum is light and stiff. You can use aluminum to decrease the flex in a shape while using the steel for the outer parts which need to be resistant and ductile.

Munro had this great diagram of what materials went where in the 3 and Y, and that was a pretty good description of what I'm talking about.

Modern casting can even drop steel cores into aluminum and plastics, to make something that's even stronger and lighter than either metal would be alone. They use this on a couple parts in the Y (Ford also does this).

-Crissa

 

[lqdchkn]

Cybertruck is supposed to be frameless so I would think there would not be a mega casting. Also it's not typically a good idea to use aluminum an steel together as galvanic reactions would eat the aluminum

STAINLESS STEEL & ALUMINUM: WHY YOU SHOULDN’T USE THEM TOGETHER AND PROPER PRECAUTIONS TO TAKE IF YOU DO

 

[Ehninger1212]

I would be willing to bet they are going to use the large aluminum casting front and rear of the cybertruck to create the super rigid assembly they spoke about during battery day which integrates the battery pack. This is part of what is needed ,from my understanding of the announcement, to get the cybertrucks price and range where it needs to be. They need to implement all of those new design aspects. Batteries, casting, manufacturing process ect. Actually I think it would be stupid not to use the technology, they have spent years developing all of this.

 

[Crissa]

Also it's not typically a good idea to use aluminum an steel together as galvanic reactions would eat the aluminum

This is true of zinc, silver, and lots of metals, tho. And you can electrically balance it or use it in reverse! They did this to restore a bunch of bridges along the Pacific Coast Highway.

https://en.wikipedia.org/wiki/Cathodic_protection

Anyhow, you always need to know what metals are touching each other. It's a pain when working with fasteners.

-Crissa

 

[lqdchkn]

I would be willing to bet they are going to use the large aluminum casting front and rear of the cybertruck to create the super rigid assembly they spoke about during battery day which integrates the battery pack. This is part of what is needed ,from my understanding of the announcement, to get the cybertrucks price and range where it needs to be. They need to implement all of those new design aspects. Batteries, casting, manufacturing process ect. Actually I think it would be stupid not to use the technology, they have spent years developing all of this.

Cybertruck is going to have a structural body, why would they add the SAME structural underbody they use on the other cars? It wouldnt make sense.