Coolbreeze704
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Anyone seriously interested in this dumb “exoskeleton” debate could, if they are bored with time on their hands, read this one post and pretty much be done with it.
One has to clarify what one means by “structural”
there’s little disagreement as to whether it’s “structural” in the sense of providing ingress protection
there’s also little disagreement as to whether it’s “structural” in the sense of providing structure upon which other items can hang (eg, the door’s window/locks mechanisms can be attached to the panel, rather than an underlying separate structure - in theory)
the rigidity you describe in the panels no doubt contributes to the two senses of “structural” above, which aren’t too controversial
the remaining sense of “structural,” is that of operational-level load-bearing - eg can the castings be lighter/less beefy, and the truck still undergo load/torsion etc., in virtue of the exterior panels
that is the controversial sense of “structure”
and it’s controversial for good reason.
Arguments that it *is* this sort of structural come in varieties of eg “Elon said so, full stop” - but close exam of anything Musk has said does NOT make explicit that Musk was talking specifically of *this* third form of structural vs the first two, uncontroversial ones, above
The *other* arguments that it’s this sort of structural go something like “there are airplanes that exist that have operationally load-bearing skin, and so the CyberTruck does too” - the logical fallacy of those assertions alone should be sufficient enough for deep skepticism. And that simply can’t be otherwise known or deduced from the armchair - it requires an understanding of exactly where, how, and to what degree the panels are attached to and across the various underlying components. Anyone claiming this line of argument is way out over their skis, unless/until they have a CT in hand, have done a tear-down, and performed some legit analysis of what the operational load-bearing capacity is both with and without the skins attached.
As for those who find it unlikely to impossible the panels will have this third, controversial, type of load-bearing structure?
Well, experts in the field (eg Munroe and others in the field) are deeply dubious that what *has* been seen of the body in black, the methods of attaching the panels, and where they attach, could amount to an engineering approach that’s anything like airplanes, etc., in this respect.
In fact, regarding this third type of “structural” one CAN from merely the armchair plus available photos winnow down the narrow extent to which any such operational load-bearing structural could be possible:
• it can’t include the windshield, glass roof, or the battery pack (those aren’t even SS panels)
• it can’t include any of the four doors, the hood, or the tailgate (those are free-hanging, articulating, panels of SS that cannot provide any operational load
• the SS trim above the doors are clipped on with basic automotive trim attachments, and are to this extent free-floating
• the two front quarter panels have more obvious and already seen attachment points that make it unlikely they are capable of being operationally load-bearing, PLUS front crashworthiness would make it unlikely Tesla would ever try for this
which, once tallied, gets us down to realizing that the entire controversy about whether the stainless can provide operational load bearing structure, is about and can really only be about? The two rear quarter-panels.
on one hand, this means the controversy is pretty trivial in respect of the truck’s overall utilization of the SS as load bearing operational structure. (And is also a pretty good indication that anyone suggesting the truck’s overall SS design provides overall airplane-like operational structure, probably doesn’t know what they’re talking about.
on the other hand, when it comes specifically to truck performance, eg payload and towing, the rear quarterpanel’s may be outsized in importance.
at the same time, there’s a strange thing here where people seem to assume that better payload and towing necessarily benefit from increased rigidity - when in fact flexibility (to a point) is a key benefit of load bearing structures.
to all this, what does Tesla have to say to date?
well, they’ve laid out pretty clearly what they mean by “exoskeleton” in their patent titled “Vehicle With Exoskeleton”.
the “Cybertruck is like an airplane” crowd conveniently overlooks the substance of the 20+ page technical document with extended discussion of what Tesla means by exoskeleton.
That patent describes only the first two, uncontroversial, senses of “structure” - as can be gleaned from the parent’s abstract (my emphasis):
“A vehicle having an exoskeleton exterior panel that provides crash resistance [ie intrusion structure] is described. The exterior panel may be formed from a monolithic metal sheet and attached to an exterior portion of the vehicle frame, and the exterior panel does not comprise an additional support structure [eg like a door] At least one component may be directly attached to the exterior panel, and the exterior panel may bear the load of the at least one component [ie structure to hang things upon]. Methods of manufacturing the vehicle are also described.”
The patent then goes on to describe how adding intrusion and hanging-upon structure in this was can save manufacturing costs, compared to eg adding anti-intrusion bars inside doors, and a frame inside a door upon which to hang components.
Here is the thrust of it, from the patent:
“Embodiments of the present disclosure relate to vehicle architectures designed such that the exterior panels of the vehicle also contribute to the vehicle's structural performance. Such exterior paneling of a vehicle may be referred to as an "exoskeleton." FIGS. 3 and 4 are views of pickup truck embodiments with exterior panel exoskeleton designs. Some embodiments of the present disclose do away with anti-intrusion bars, and instead use a durable unitary exterior panel (e.g. door panel) to provide impact protection. Thus, the exoskeleton design described herein eliminates the inner door structure and protection system, and uses only a unitary outer exterior panel. In this design, the hinges and latches for opening and closing the door, as well as door component such as windows and motors mount directly to the exterior panel. This approach may be applied to side door, roof, hood, fender, and trunk (or liftgate) assemblies of the vehicle. The exoskeleton approach may result in significant reduction in manufacturing footprint and costs.”
What does the patent say, if at all, about providing overall operational load-bearing structure?
It *DOES* talk about it! But there’s a catch:
“In another embodiment [eg another concept that *could* be implemented], other externally facing portions of the vehicle [ie other than the doors etc] would also use the exoskeleton concept. For example, in a typical conventional vehicle a welded closed vertical section between the side doors of a vehicle acts as a beam to react against side crash forces applied to the body by an impacting vehicle, resist vertical loads applied to the roof in a roll over even and react seat belt loads for the front seat passenger, among other smaller forces. In contrast, this body side structure construction would convention have a thin, cosmetic outer panel welded to a structural closed section (typically one or more inner stamped sections welded to one or more outer stamped sections). However, embodiments of the present disclosure relate to an exoskeleton construction, where the outer structural reinforcement(s) are made from a single structural panel that provide the same load advantages as the more complex conventional structure, but also serve the cosmetic functions of the customer facing areas of the vehicle.”
Here, they are now describing a different possible utilization of the patent concept, along the lines of the “airplane” concept, and the 3rd type of “structure.”. The vast majority of the patent deals with the other two kinds of structure, and in doors, etc. So the patent DOES talk about the third type of structure.
But in the next line is the catch:
“As such, a vehicle having a vehicle frame is disclosed, wherein the vehicle comprises an exterior panel. In some embodiments, the exterior panel does not comprise an additional support structure.
Here they are describing the “origami” SS frame of lore. The “not comprising an additional support structure” is patent-speak for “the exterior panel itself IS the frame and there is not any ‘additional’ under-frame to which the panel is combined.”
This same distinction - between using the SS for the first two kinds of “structure” vs the third type of “structure” - is carried through in the manufacturing discussion, for example:
“The monolithic metal sheet may be manufactured by providing an initial monolithic metal sheet, cutting the initial monolithic metal sheet to form a cut monolithic metal sheet, and shaping the cut monolithic metal sheet to form the monolithic metal sheet. In some embodiments, the monolithic metal sheet is in the shape of a door panel. In some embodiments, the monolithic metal sheet is in the shape of an external portion of a frame.”
All-in-all:
• the patent LARGELY describes using SS panels to accomplish the first two types of “structure”
• the patent only BRIEFLY describes using SS to form the frame itself, which frame itself forms an “external” Frame is not “additional” to any other frame, but is itself an external frame
• and so, relative to what we see in the present production Cybertruck, we very much see another “additional” frame, to which the panels are attached, and uncrontriversially do exactly what the patent describes most: providing ingress and hangs-upon structure
So here’s the most concerted, detailed, indisputable conversation Tesla has ever had regarding what it means by “exoskeleton.” And it is almost exclusively discussing the first two types of “structure.” When otherwise the patent briefly describes anything like the third type of structure, it does so by describing a method of construction that does not square with the production Cybertruck we’ve seen.
Anyone suggesting Musk has said otherwise, hasn’t paid close attention and is hearing primarily with their hopium biases.
Anyone asserting from the armchair that “the Cybertruck” SS is operationally structural (1) is glossing over that we could only possibly be talking about the rear quarterpanels, and (2) has ZERO information that would allow them to assert this on any basis (assuming they haven’t done an tear-down and load-path tests. And meanwhile, the Tesla patent doesn’t square with these armchair assertions at all.
Instead, the patent describes what we’ve seen in the doors, hood, and tailgate of the production CT. As for the rear quarterpanels, the patent doesn’t square at all with the construction method we’ve seen.
Is it possible that, when it comes to the rear quarterpanels, Tesla has done some off-patent form of engineeering whereby - unlikely as it seems - the rear QPs are somehow attached to the cab/castings in such a way as to *contribute* to operational load bearing structure? I suppose it’s possible, but the more images we see, and when squares with what Tesla has said in the parent, it sure seems unlikely.
And in any event, the crowd of “the SS provides operational load-bearing structure” is at best overstating the point (only the rear QPs are even theoretically possible), and also asserting as fact from their armchair things they can’t possibly know, not to mention things at odds with the only information Tesla has explicitly described.
SO YES - IT’S EXACTLY THE TYPE OF ‘EXOSKELETON’ TESLA HAS DESCRIBED, INSOFAR AS TESLA HAS ONLY DESCRIBED PROVIDING INGRESS PROTECTION AND HANG-UPON STRUCTURE.
BUT NO - TESLA’S EXPLICIT DESCRIPTION OF HOW OPERATIONAL LOAD-BEARING STRUCTURE WOULD BE ACCOMPLISHED, IF EVER, IS NOT EVIDENCED IN EVEN THE REAR QPs OF THE PRODUCTION CT.
IF they’ve done something here off-patent, NOBODY here has the ability to surmise it from their armchair.
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