Exoskelton fake news?

[Crissa]

I think of "exoskeleton" as a clever marketing term that Tesla came up with to describe their unibody frame construction. All manufacturers do this and Tesla is no different.

Yes and no. Yes, the Cybertruck is a unibody. But no, other cars haven't used a stressed skin like the Cybertruck's. And all of them have used an assembly like the Tesla megacasting, albeit an assembly, not a single piece.

-Crissa

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[Vrakpant]

Watch video at 2:15

 

[VolklKatana]

It is very reasonable to think the drivetrain and suspension components would directly bolt to the exoskeleton. Cars have been built like this since the 1960s. I restored an old Camaro that was built this way. And don’t tell me, “of course Tesla wouldn’t use 60 year old technology!”. Formula 1 cars do the exact same thing, bolt suspension and drivetrain to the monocoque (exoskeleton) body.

I totally disagree with this statement. In older cars, suspension and drivetrain components are attached to structural and reinforced parts of the vehicle, not just the sheetmeatal underside of the cabin or bed. This is why the Cybertruck drivetrain won't just be bolted to the bottom of the exoskeleton, it needs to be reinforced. This where the casting comes Into to play, giving electric motors, and suspension components a place to attach to, while also likely helping to make the bed capeable of handling the larger loads.

 

[SSonnentag]

Even a tortoise has bones.

 

[BillyGee]

Came back to this thread after the weeknd, I've been making this face the whole time I'm getting caught up.

 

[flowerlandfilms]

Even a tortoise has bones.

...indeed, in fact my understanding is that the shell is an extension of its spine...

 

[Dids]

I think if the cast aluminum components are a major structural portion of the frame then this may be a point of failure. This is based on my experiences in the past with repairing cast aluminum.



The other problem is you are not going to be able to weld the cast aluminum to the stainless exoskeleton. It will need to be bolted or bonded (glued) together. This is not ideal. Having a completely stainless exoskeleton welded to mounting rails for the drivetrain, etc would be a more homogenous way to do it. My guess is that the aluminum subframe was chosen purely on the financial benefits (cost savings).





I do not have blind confidence in Tesla’s cars. I have a 2018 Model 3 that has just over 30k miles and my car has noticeable creaks and rattles. My Tesla replaced a 2009 X5 diesel with >130k miles that had none of these issues. Do I regret getting the Tesla? Definitely not, all of the positives easily outweigh the negatives. My point is that Tesla’s cars and engineering are not perfect.





I haul 12k+ dump trailers and equipment all over job sites. Regularly, I am hauling heavy loads over non-graded hillside dirt lots that constantly tweak the frame back and forth. This gets repeated over and over all day long, non-stop. I also have a 10k toy hauler that gets pulled deep into the National forests over very rough dirt roads.



I have no doubt that the Cybertruck will be able to handle hauling loads off-road from time to time. I am just not sure a cast aluminum frame is ideal to tolerate this repetitively day in and day out.



I will certainly find out. like I’ve stated before, I have no intention on canceling my Cybertruck order.





Essentially all cars are built this way, including all of Tesla’s cars. As BillyGee stated, the Cybertruck’s exoskeleton design is basically just a unibody frame like every other car. It has the exact same components (aprons, A/B/C pillars, quarter panels, floor pans and mounting rails) that every other modern car has.



The groundbreaking part of the Cybertruck’s design is that the unibody frame does double duty at the body panels. This is a genius cost saving way to make a vehicle.

No it is not the same as unibody. Unibody has the frame built into the body with stress carrying members. This would be an exoskeleton with the skin being the stress carrying member. Of course it must still have b pillars. There has to be something to mount the door latch onto. Also calling the cast pieces an aluminum frame is incorrect. Yes they are a frame but they are not the vehicles frame. In other words the casts do carry stresses but they are not the vehicles stresses

 

[Dids]

...indeed, in fact my understanding is that the shell is an extension of its spine...

A tortoise doesn't have an exoskeleton its an endoskeloton armoured reptile. The shell is not its frame.

 

[flowerlandfilms]

A tortoise doesn't have an exoskeleton its an endoskeloton armoured reptile. The shell is not its frame.

...but the shell is part of its skeleton no?...
...so isn't it kind of both?...

 

[Crissa]

...but the shell is part of its skeleton no?...
...so isn't it kind of both?...

No, the shell isn't the source of the structure.

It's like how unibody cars have a shell, but not an exoskeleton. The body panels come off ^-^

-Crissa

 

[Dids]

No, the shell isn't the source of the structure.

It's like how unibody cars have a shell, but not an exoskeleton. The body panels come off ^-^

-Crissa

Don't do it! Turtles hate it.

 

[Dids]

...but the shell is part of its skeleton no?...
...so isn't it kind of both?...

Yes its part of the skeleton but a true exoskeleton is an invertebrate. Since turtles have a backbone albeit one that is spread out into a whole body house they are very much like a uni body structure.

 

[Texas Bart]

No one said cast aluminum . It could be cast stainless steel. Also no one said cast frame. The frame of the CT is the external cold rolled 30x stainless steel. Elon said CT requires an 8 ton casting machine because its a bigger part.

I believe it's 8000 tons.

 

[Crissa]

Yes its part of the skeleton but a true exoskeleton is an invertebrate. Since turtles have a backbone albeit one that is spread out into a whole body house they are very much like a uni body structure.

Turtles have articulation at least tortoises do...

...But even crabs have bits of structure that sticks inward for their joints and gills and organs attach to. That's the function if the interior castings and such in the Cybertruck.

-Crissa

 

[Sonnus]

I'm sorry to drag this thread even further though the gutter but here it goes...

I think the main disagreement is the interpretation of "exoskeleton". When Tesla announced this I immediately assumed that the 3mm flat exterior panels would be combined with thinner stamped and welded stainless panels on the inside (unibody or semi-monocoque construction). I have had lots of experience working with 1/8" 304L and 316L cold rolled sheet, just like what the Cybertruck uses. There is no decent way to make the visible 3mm flat skin exterior panels of the Cybertruck strong enough (torsionally) without internal structural members. It would be a flimsy mess. Heck, when you look at the picture of the Cybertruck "exoskeleton" on Tesla's website you can clearly see there are internal reinforcements (A/B/C pillars). And no, the pillars are not just there to bolt door hinges to. These are critical structural members of the frame (think of webs in a steel truss).

A good way to illustrate this is with a cardboard box. If all 6 sides of a box are securely taped in place then the box is very rigid. If you remove just one side of the box then it becomes extremely flimsy.

If the exoskeleton of the Cybertruck does not have a strong underbelly structurally fixed to the outer panels (either structural battery pack, cast aluminum or stainless welded floor pans and cross-members) then the frame would have very poor torsional rigidity.

And now back to the original topic of this thread... I am positive that the aluminum casting on the Cybertruck will be a major structural member of the frame in order to achieve the necessary torsional rigidity. It may be bolted, maybe bonded with resins, maybe even friction welded to the stainless panels. I would have just preferred that the underbelly part of the frame was stamped and welded stainless steel, like the prototype almost certainly is, instead of using a cast aluminum member.