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

[Ogre]

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!

They crush the passengers to save the _______?

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[greggertruck]

Lot of cool perspectives here, I had seen an old post too that I read through as well. Really looking forward to the event whenever, hoping that provides some clarity.

 

[rr6013]

the term "exoskeleton" is at least 70% marketing talk
<snip>

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

<snip>

Until an engineering walkthrough is performed ala Munroe and Associates. tl;dr

Takeaway the exoskeleton. That leaves the Tesla structural batterypack(See:above). It is max. 8” depth x 69”+ width x 150” length with two alum. castings chemically bonded at its distal ends.

How many sandbags can it carry? Without the exoskeleton “body” providing structure to support the battery “pack” it’s a crump-wimp; collapsing inward on itself. Castings are cantilevered in free air! BUT Integrate the two and *superstructure* with foam Oreo cookie on the bottom.

IDK how to calc an Oreo cookie. I’ll cop to that marketing hype. But I buy-in to the “negative mass” calculation that transform battery dunnage weight into working structure that lightens the mass of the pack in a net gain for exoskeleton range efficiency. That’s just too fricking alien to ignore.

Exoskeleton is a sum of parts that all contribute.

1. front fender - ornamental
2. front & rear doors - structural. Engineers make every part earn its way onto a platform. Doors are ornamental only for access up to the point they close, latch and lock into the frame around the door. At that moment a side impact crash bar inside the door becomes functionally engaged in its structural frame. Critically, the frame around the doors is fitted so that in the door-closed position the exoskeleton is able to calculate doors-closed to its added strength which contributes to overall exoskeleton rigidity.
3. the rear fender and sail pillar - structural , rigid. IDK% of load transfer forward via sail pillar thru the exoskeleton truss onto front casting, suspension and wheels. Wild ass guess…Tesla tunes Cybertruck suspension 50/50 weight distribution completely MTY(empty). Loaded, curb weight distribution may approach 35/65 max. to keep front wheels on the ground. The fact that front castings do not require 9k IDRA press tells that, that front casting isn’t taking on heavy loading up front. Takeaway is that 100% of exoskeleton pickup bed eight cannot bear directly onto rear casting and rear wheels as conventionally seen as flexible ladder-frame pickups do, squatting under load. Cybertruck is so stiff that the front wheels would come off the ground before it would ever flex.
4. vault cover - non-struct.
5. frunk hood - non-struct. It is engineered to sheer-off up the front windscreen as crash slope from frontal impact force
6. windscreen and rear backglass - windscreen frame structural. Windscreen glass Armorglass is structural. Backglass IDK. Rear window glass frame IDK. BUT the panel below the rear backglass is the most critical structural component in the Cybertruck exoskeleton design. That sheet of vertical steel spans the full width from side-to-side comprising what engineers refer to as “sheer panel”. Its the major vehicle structure preventing A-frame exoskeleton structures on either side from inward collapse or outward cant. Importantly, it figures into the pickup bed+sail pillar box structure load calculations and plays an integral part in the transfer of forces through to both sides of the exoskeleton A-frames. ///////////////// sidebar \\\\\\\\\\\\\\
   Geek note that the Cybertruck exoskeleton has four sides(outer driverside, inner driverside, inner passenger side, outer pass. side) A side‘s strength is measured by the distance between the outer and inner calculated as a cumulative sum total. The measured distance separating Left-Right sides calculates the final exoskeleton design strength properties.
7. underbody - unlike ICE frame-on-body and unibody design, Cybertruck has a sheet steel box cum batterypack underbody rather than a steel frame front to rear or a stub-frame as in the case of unibody. Its structural integrity, @JBee alludes does little to nothing in the sense of structure. That’s only correct up until the moment the perimeter of the batterypack joins with the exoskeleton permanently. *Superstructure* From that moment onward the batterypack box structure gains strength from the exoskeleton above it. So too the pack and castings provide structure to close the large box formed by the coming together of the two. Critically, the “skate” ass’y(i.e. rolling chassis wheels, tires, suspension, castings, batteries, and batterybox) provides the four structural landing points needed by a vehicle exoskeleton to translate all load to ground.

Fundamentally a bellypan used in conventional ICE frames are non-structural coverings. Whereas in the case of an exoskeleton that bellypan is structural. And even though structural, requires added benefit of plate steel rock guard protection - lest solid, sharp objects tear into batteries just above bellypan. Structural bellypan isn’t rockproof. IDK waterproof but s/b(should be)up to 3 atmospheres. Tesla should put forward a standard EV rating for Elon’s waterproof as “ IP6” denotes for electrical components.

 

[Crissa]

They crush the passengers to save the _______?

Passengers flex and absorb some of the effects of the collision.

Spouse has a story of being a teen, in a hoopty car that had a wheel that was malfunctioning, everyone was meant to squish to the driver's side so they wouldn't pop the spare tire on the passenger side...

-Crissa

 

[HaulingAss]

The fact that front castings do not require 9k IDRA press tells that, that front casting isn’t taking on heavy loading up front.

The needed tonnage of the IDRA gigacasting press for any given cast piece is a function of the surface area of the cast part, not how much load it will need to take. The ton rating of an IDRA casting machine is the amount of pressure required to hold the two halves of the mold together as high pressure, molten alloy is injected inside the two halves and that is determined by how quickly the mold halves are filled (pressure) and the area of the casting perpendicular to the hydraulic press.

A small, thick casting can be made with a 6K ton machine but that does not imply it won't be able to be heavily loaded. That said, the load bed is over the rear wheels so, of course, the rear subframe will take higher loads than the front.

 

[Cyberman]

They crush the passengers to save the _______?

...integrity of the vehicle for the next user!!!
Cars aren't cheap in the new UUSR.

 

[Ogre]

...integrity of the vehicle for the next user!!!
Cars aren't cheap in the new UUSR.

I hear many are trading their first born son for one.

 

[Cyberman]

I hear many are trading their first born son for one.

Sadly, with the effects of the new war/covid-borne inflation, the rate is 18 billion of your children per vehicle/glorified wheelbarrow.

 

[ED_SFO]

I think it will still have a traditional "frame". The exoskeleton part of what he was talking about is because the body panels are made up of thick stainless steel, which helps stiffen the vehicle vs typical body panels which are thin sheet metal that flexes. Airplanes still have frames because you still need to bolt the skin to something. Imagine u built a square frame from 4 pieces of equal length 2x4's that are 4 ft long with screws...on it own it might be solid but will still flex. Then screw on some thin sheet metal on both sides..it would be more solid but will still flex at the upper limit. Now bolt on 2mm thick stainless steel to that square and it will not flex even at extreme pressures. Thats my take on the exoskeleton Elon was talking about not actually how it's made or if it's a different process. It's how the stainless steel is used to help keep the truck rigid, the exterior panels is being more useful than just creating a shape.

 

[Mini2nut]

it sounds like Tesla is copying some aircraft manufacturing techniques.

 

[Deleted member 12457]

I didn't read every comment in detail but we know the rear of the CT will have a cast aluminum frame because that's what the gigapress is for. The front might also be cast just like on the Model Y and the structural pack is also considered a frame so what's the big deal with people wondering if the CT will have a frame. Of course it DOES. Just because it won't have two long box beams like old rigid trucks created since the first truck was ever built doesn't mean it won't have a frame. Halloween must be getting to people.

 

[rr6013]

I think it will still have a traditional "frame"

You and many others.

Imagine the surprise as people who buy a snow plow or winch – they require a special mount to the Cybertruck. IDK about a 5th wheel towing hitch.

Anything that traditionally uses the frame of a vehicle will not immediately “just work”. Hydraulic car lifts will damage a Cybertruck unless specifically positioned at engineered lift point(s).

Many owners will be a victim to the tow truck driver who knows not to tow a Cybertruck on its own wheels but hooks up the chains and tie-downs in the wrong place out of cocky confidence.

Cybertruck enjoys that Range Rovers and others came before it. They educated people in automotive that some trucks are special handling or big bills ensue. Victims should be few, but there’s always that guy. And how is a significant other or employee to know, much less jawbone against an automotive professional whose there to help in the first place. Those are the power dynamics, that befall a special vehicle owner if anyone is under assumptions - wrongly.

 

[TyPope]

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".

There will be the unibody type of regular old stamped steel. This vehicle will not be simply a layer of steel on the outside. A good way to look at it will be to envision the doors. There will be a supporting stamped piece attached to each door skin (the Outerpanels). The window and doorlock stuff will be between the two and the interior plastic bits will be attached to the stamped piece.

What you WON'T see is a ladder-type of frame like what almost every other truck has... Honda Ridgeline being the first exception I can think of.

There will be the front casting, battery pack with seats attached to it, and a rear casting. Motors will be assembled to that as well as thermal management (cab and battery). The body/exoskeleton will be placed down on that. Most likely, the doors, hood, tailgate, under-bed section, fenders, bumpers, sail doors, vault cover, tailgate, rocker panel, and other such bits will have already been attached to the exoskeleton.

Then, Interior wiring, ergo pieces, display, dash, 4x4 light (whatever that cool ass light is called) etc. will be placed before the roof glass and windshield.

Wheels will be assembled when it makes the most sense to do so.

The exoskeleton mostly just does away with internal longitudinal stiffening ribs and braces... Basically, a fancy unibody using the front/rear castings, structural battery pack, and outer skin for structural strength instead of a heavy ladder frame.

 

[RVAC]

I didn't read every comment in detail but we know the rear of the CT will have a cast aluminum frame because that's what the gigapress is for. The front might also be cast just like on the Model Y and the structural pack is also considered a frame so what's the big deal with people wondering if the CT will have a frame. Of course it DOES. Just because it won't have two long box beams like old rigid trucks created since the first truck was ever built doesn't mean it won't have a frame. Halloween must be getting to people.

Sure, body-on-frame, unibody and exoskeleton are all frames ... doesn't mean they are the same thing though.

 

[Deleted member 12457]

Sure, body-on-frame, unibody and exoskeleton are all frames ... doesn't mean they are the same thing though.

The topic is about whether there is a frame underneath (the body) and most of the discussion is ignoring the fact there is a frame underneath the exoskeleton and body. I'm not saying they're the same thing, I'm simply saying the CT has a structural frame under everything.

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