Understanding The Exoskeleton / Body -- is there a frame underneath?

greggertruck

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You guys don't all think it's one piece of steel all just bent, right? I've had a couple discussions with confused people.

There is in fact a frame under there, the bent steel mounts to the exoskeleton.

Right???
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I believe there is a frame, although not a traditional one. Coupled (throupled?) with the structural battery pack, the pseudo-frame, and exoskeleton (and doors and glass) come together to make a really solid marriage of components that are on another level altogether.
 

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You guys don't all think it's one piece of steel all just bent, right? I've had a couple discussions with confused people.

There is in fact a frame under there, the bent steel mounts to the exoskeleton.

Right???
No, there's not 'a frame inside'.

It's a type of unibody. What's underneath doesn't work without the exoskeleton being there. It's the other half of the frame inside.

-Crissa
 

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You guys don't all think it's one piece of steel all just bent, right? I've had a couple discussions with confused people.

There is in fact a frame under there, the bent steel mounts to the exoskeleton.

Right???
There's no chance that the whole Cybertruck is one big piece of stainless folded up. It will be several pieces bonded together (glue? welds? screws? that stuff on the floor of theaters?)

But, my understanding of the exoskeleton is that the body structure will consist of castings, HV pack, and origlamied stainless. There will obviously be stamped steel for things like brackets etc. but there won't be a traditional "frame".
 


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greggertruck

greggertruck

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No, there's not 'a frame inside'.

It's a type of unibody. What's underneath doesn't work without the exoskeleton being there. It's the other half of the frame inside.

-Crissa
That’s highly confusing and sounds like stated fact that we don’t have confirmed?
 

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Un-SWAG

Using the terminology “frame” with respect to an exoskeleton can only describe the effect created by the A-pillar–B-pillar openings and B-pillar–C-pillar that form the door and window frames.
Tesla Cybertruck Understanding The Exoskeleton / Body -- is there a frame underneath? 5741DC5A-88C3-42DF-AC17-41DD6BC6EC05

Taken together the two openings span the distance from bottom rocker to Roof line to form an open truss-structure of the Cybetrtruck exoskeleton.
Tesla Cybertruck Understanding The Exoskeleton / Body -- is there a frame underneath? 79CB1C90-2047-4143-8179-D1D160D3DB8D


The resultant A-frame transfers lateral load to the truss terminal bearing endpoints downward and in shear to what it is bolted to. In the case of a building truss that supports roof loads it’s bolted to wall structure.

In a vehicle application the truss is bolted to wheels at each end supported by steel spring suspension. A truss however does not make a frame. The distance measured from the bottom to top opening created by the door frames determines the strength of the truss member. Cybertruck has two such truss members one on each side of the vehicle.

The distance separating the two trusses increases structural integrity, as seen later. Kind of material, s.s., increases strength. Critically, skinning the truss in sheet s.s. metal is what changes the truss into an exoskeleton.

The exoskeleton becomes a three sided boxed beam in engineer-speak. An A-frame with metal top chord and metal on two sides. An engineer performs load calcs on that basis for both metal skinned trussed sides of Cybertruck.

The two trusses are connected by cross beams across and to each top chord at several roof locations forming rectangular frames. Those are added halving the amount of load each truss would individually experience by spreading it across two trussed structures.

The bottom chord of a truss is non-bearing. In the case of Cybertruck entirely mechanically fixed to the perimeter of its batterypack. Ordinary and normal load force that would be transferred along the bottom chord to terminal bearing points(i.e. wheels) is now also in communication with load forces from the attached batterypack.
Tesla Cybertruck Understanding The Exoskeleton / Body -- is there a frame underneath? 30A52C2C-C33F-4331-99F2-8830B56332F8


Finally the batterypack topsheet(i.e. floorpan) connects the two exoskeleton A-frames completing a box structure. And that is the final embodiment that engineers will use to calculate ultimate load strength of the exoskeleton.

In the use case of a vehicle, load force calculations against the exoskeleton will be applied in all directions even from the ground up. As well as rollover and blunt force impacts that must be accounted throughout the boxed frame structure of the exoskeleton.

A small argument for the batterypack acting as frame has merit. Indeed it will carry load below CG(center of gravity), pickup casting loads and transfer lateral forces into the exoskeleton. In this capacity, the batterypack adds strength, rigidity and absorbs smaller vibrational forces that the exoskeleton would pickup. By the batterypack acting as frame and foam attenuating forces much of the road vibration will never reach the passenger compartment. No small accomplishment, that.

Interesting note: Tesla front castings do not span across the exoskeleton to form a ”cowl” nor “firewall”. In the first instance a cowl would translate forces into the passenger compartment where only human wet meat could absorb. In the second, first principles a fire wall is no longer needed nor necessary. All front casting forces are directly inline with the exoskeleton and door frames.
 

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We don’t know.

Wont know until there is a tear down.

Based on the description from Tesla, the steel body is the frame. If it’s not structural, it’s a giant waste of material.

Most likely there will be some pieces like the B pillar that will be “frame” but you won’t have an inner body like a typical unibody car.
 

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You guys don't all think it's one piece of steel all just bent, right? I've had a couple discussions with confused people.

There is in fact a frame under there, the bent steel mounts to the exoskeleton.

Right???
This is confusing. Unless you are familiar with modern trucks.
Modern trucks have a frame. Then they put the cab (body) on the frame. Bolt on the fenders. And probably slide the engine in to rest/ bolt on the frame. Then put the doors on. Then slap the bumper on. Then the have to put the bed on the frame as well. Cyber truck should will have a structured battery. Then cybertruck main body. (Literally just take the doors completely off the cyber truck.) and that’s basically it.
see how Tesla is stream lining… literally the bed/cab/fender/ bumper are all one peice. Which should speed up production and make it cheaper.
 

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You guys don't all think it's one piece of steel all just bent, right? I've had a couple discussions with confused people.

There is in fact a frame under there, the bent steel mounts to the exoskeleton.

Right???
Lets start with the common definition of "exoskeleton":

noun
  1. a rigid external covering for the body in some invertebrate animals, especially arthropods.
Technically, nearly every car has a "rigid" external covering in the form of body panels. But in the case of the CT this has been optimized, in that some of the external cover is also load carrying.

There have been various conversation on various threads here, and I'm still of the opinion that the term "exoskeleton" is at least 70% marketing talk, like the "vault". This is mostly because if you subtract the door opening areas, frunk, side doors, sail doors and Vault cover, there is little more than the front and rear fenders left to be load carrying "exoskeleton" cover.

Tesla Cybertruck Understanding The Exoskeleton / Body -- is there a frame underneath? CT Panels


Overall there is a question of what parts of the car are structural at all, how much load they carry, and how they transfer those loads to other parts of the vehicle.

Like every wheeled vehicle out there, except for in a collision, the only load interaction with it's surroundings is through the contact patch of the tyres. That means the vehicle itself, or if you put people or payload into the vehicle, all that "load" needs to transfer to the tyre patch.

Tesla Cybertruck Understanding The Exoskeleton / Body -- is there a frame underneath? hy6gpxl3rzwisgt49ynl


So lets do some load paths so we can navigate what is going on. The structural battery pack is the largest singular mass in the construction of the vehicle and it's static load path would be:

a) Structural pack, cabin rollcage, front and rear casting, suspension then wheels.
b) People would be added in front of the structural pack pathway above
c) Bed Payload in the rear bed would be predominately bed, rear cast, suspension, wheels. There could be a bit of rigidity help from the "exoskeleton" interior bed sidewalls.
d) Frunk payload - front casting, suspension then wheels.

Now the dynamic load paths would be a different, and where the exoskeleton might play a larger roll:

In Acceleration/Deceleration: Tow ball and trailer load, bed payload, rear cast, suspension and tyres, and then cabin rollcage, structural pack, front cast suspension and wheels. How much load is transferred where depends on how much traction each tyre patch has.

In sideways Acceleration around a corner: a combination of the above load shifts plus more load on the outside of the corner by the change of directional inertia.

In these dynamic load cases most of the loads are not transferred to the outside skin of the vehicle, except maybe the interior side walls of the bed, which would both give extra torsional rigidity and better point load distribution on the bed area itself.

To transfer the loads into the "exoskeleton skin" would actually mean transferring them from the structural pack to the fender skin and then back to the cast, suspension and wheel instead. Or for the rear bed, from the bed to the rear fender skin and back to the cast, suspension and wheel. It is a detour to do so and would make no sense if the aim is to get the load into the wheel, which has to go through the cast and suspension.

Let's do each part of the "outside skin exoskeleton": (which I've copied from my other posts)

  1. front fender - could be used structurally but needs deformability for front and offset crumple zone - the outside fender skin is not in right location to transfer loads to the inside of the suspension arms
  2. Front and rear doors - are only attached to the cabin structure using hinges and a door lock - the the skin is main structure that holds the door together (as is on most cars) and provides side intrusion protection but carries no load until the door is pressed into the cabin frame from a side impact
  3. The rear fender and sail - these will most likely transfer some dynamic bed load offer torsional rigidity in the bed, but most of the load carried in the bed will go straight into the rear cast that holds up the bed and attached to the inside of the suspension arms
  4. Because the vault cover moves it provides no structural component and needs to be supported by the midgate and rear fender sail walls
  5. The frunk hood also moves and like the doors will only add to the "exoskeleton" if compressed into the cab frame - I'm not sure how they will do pedestrian impact using 3mm steel. The hood will at least need suspension to absorb some impact and reduce g force
  6. The windscreen and rear glass - these are probably the largest structural components on the CT that fit the "exoskeleton" definition - but they can be found on heaps of other vehicles including other Teslas, and Tesla wasn't the first to use glass like that either. (Think windscreens)
  7. Underbody - technically the sandwich panel structural pack is also on the outside skin, but the whole battery structure, because of its thickness, can hardly be called a "covering" to fit with the definition, let alone MY doesn't call it that either. From what we have seen so far underbody panels will be added to the front rear castings, as having a thick SS skin across those parts in a flat orientation does little to nothing in addition to what the casts already do, except make maintenance and repairs more difficult and offer offroad rock skid protection.
Given the above it would seem clear that although they like calling it a "exoskeleton" it is in fact a hybrid of all the various elements it's made of, with the structural pack, cabin rollcage and glass, and castings taking most of the load, and allowing the rest of the vehicle to be built lightweight and cost effective. The result is that each element, even the motor housings that sit inside the cast have some ability to sustain and transfer forces, and each components adds to the overall structure, in that no one thing is the sole source of it's total structure.
 
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Crissa

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That’s highly confusing and sounds like stated fact that we don’t have confirmed?
I don't know what's confusing about it. It's depicted as a unibody. Unibodies do have structure inside, but modern ones don't work without some of the skin; the Cybertruck is supposedly this, but further.

-Crissa
 

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Lets start with the common definition of "exoskeleton":

noun
  1. a rigid external covering for the body in some invertebrate animals, especially arthropods.
Technically, nearly every car has a "rigid" external covering in the form of body panels. But in the case of the CT this has been optimized, in that some of the external cover is also load carrying.

There have been various conversation on various threads here, and I'm still of the opinion that the term "exoskeleton" is at least 70% marketing talk, like the "vault". This is mostly because if you subtract the door opening areas, frunk, side doors, sail doors and Vault cover, there is little more than the front and rear fenders left to be load carrying "exoskeleton" cover.

CT Panels.png


Overall there is a question of what parts of the car are structural at all, how much load they carry, and how they transfer those loads to other parts of the vehicle.

Like every wheeled vehicle out there, except for in a collision, the only load interaction with it's surroundings is through the contact patch of the tyres. That means the vehicle itself, or if you put people or payload into the vehicle, all that "load" needs to transfer to the tyre patch.

hy6gpxl3rzwisgt49ynl.jpg


So lets do some load paths so we can navigate what is going on. The structural battery pack is the largest singular mass in the construction of the vehicle and it's static load path would be:

a) Structural pack, cabin rollcage, front and rear casting, suspension then wheels.
b) People would be added in front of the structural pack pathway above
c) Bed Payload in the rear bed would be predominately bed, rear cast, suspension, wheels. There could be a bit of rigidity help from the "exoskeleton" interior bed sidewalls.
d) Frunk payload - front casting, suspension then wheels.

Now the dynamic load paths would be a different, and where the exoskeleton might play a larger roll:

In Acceleration/Deceleration: Tow ball and trailer load, bed payload, rear cast, suspension and tyres, and then cabin rollcage, structural pack, front cast suspension and wheels. How much load is transferred where depends on how much traction each tyre patch has.

In sideways Acceleration around a corner: a combination of the above load shifts plus more load on the outside of the corner by the change of directional inertia.

In these dynamic load cases most of the loads are not transferred to the outside skin of the vehicle, except maybe the interior side walls of the bed, which would both give extra torsional rigidity and better point load distribution on the bed area itself.

To transfer the loads into the "exoskeleton skin" would actually mean transferring them from the structural pack to the fender skin and then back to the cast, suspension and wheel instead. Or for the rear bed, from the bed to the rear fender skin and back to the cast, suspension and wheel. It is a detour to do so and would make no sense if the aim is to get the load into the wheel, which has to go through the cast and suspension.

Let's do each part of the "outside skin exoskeleton": (which I've copied from my other posts)

  1. front fender - could be used structurally but needs deformability for front and offset crumple zone - the outside fender skin is not in right location to transfer loads to the inside of the suspension arms
  2. Front and rear doors - are only attached to the cabin structure using hinges and a door lock - the the skin is main structure that holds the door together (as is on most cars) and provides side intrusion protection but carries no load until the door is pressed into the cabin frame from a side impact
  3. The rear fender and sail - these will most likely transfer some dynamic bed load offer torsional rigidity in the bed, but most of the load carried in the bed will go straight into the rear cast that holds up the bed and attached to the inside of the suspension arms
  4. Because the vault cover moves it provides no structural component and needs to be supported by the midgate and rear fender sail walls
  5. The frunk hood also moves and like the doors will only add to the "exoskeleton" if compressed into the cab frame - I'm not sure how they will do pedestrian impact using 3mm steel. The hood will at least need suspension to absorb some impact and reduce g force
  6. The windscreen and rear glass - these are probably the largest structural components on the CT that fit the "exoskeleton" definition - but they can be found on heaps of other vehicles including other Teslas, and Tesla wasn't the first to use glass like that either. (Think windscreens)
  7. Underbody - technically the sandwich panel structural pack is also on the outside skin, but the whole battery structure, because of its thickness, can hardly be called a "covering" to fit with the definition, let alone MY doesn't call it that either. From what we have seen so far underbody panels will be added to the front rear castings, as having a thick SS skin across those parts in a flat orientation does little to nothing in addition to what the casts already do, except make maintenance and repairs more difficult and offer offroad rock skid protection.
Given the above it would seem clear that although they like calling it a "exoskeleton" it is in fact a hybrid of all the various elements it's made of, with the structural pack, cabin rollcage and glass, and castings taking most of the load, and allowing the rest of the vehicle to be built lightweight and cost effective. The result is that each element, even the motor housings that sit inside the cast have some ability to sustain and transfer forces, and each components adds to the overall structure, in that no one thing is the sole source of it's total structure.
I think I read somewhere that in Russia, passengers are part of the structure. During a crash, the passengers are expected to hold on to the "grabber" handles provided so as to help absorb the impact. Making use out of everything! 😁
 

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I think I read somewhere that in Russia, passengers are part of the structure. During a crash, the passengers are expected to hold on to the "grabber" handles provided so as to help absorb the impact. Making use out of everything! 😁
Lol reminds me of the real reason there's grab handles on cars:



 

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I think I read somewhere that in Russia, passengers are part of the structure. During a crash, the passengers are expected to hold on to the "grabber" handles provided so as to help absorb the impact. Making use out of everything! 😁
In Soviet Russia, car drives you
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