PSA: Cybertruck body shell exoskeleton is not one contiguous piece of bent steel

[Jhodgesatmb]

My ship tracker showed it at dock when I mentioned it.

Sadly (very sadly) I do not see anything on the discharge list that is very heavy :-( I am hoping that I just don't know how to use the tool.

 

[Qball]

I am sure that you have seen the unveiling where they hit the door with a sledge hammer. The whole idea was to show that the driver and passengers would be protected against a bullet. It may have nothing to do with the strength of the exoskeleton but it has everything to do with the concept of Cybertruck as an urban-assault / post-armageddon vehicle. So they might as well use the same material as the rest of the exoskeleton.

Yes, I saw that and got a giggle but heavy doors could be unnecessary weight/mass. I get the why not part but still don’t get the why yet, a ton of extra mass for cool factor isn’t how Tesla rolls normally, they have always been the king of eliminating unnecessary. Goal of design is simplicity, efficiency and mass scale production. If even 1lb of steel saved per CT at 1 million CT that’s 1 million pounds of steel, not to mention better range/efficiency.

Those who do not understand importance of fraction of a penny can not make a dollar.

 

[Jhodgesatmb]

Yes, I saw that and got a giggle but heavy doors could be unnecessary weight/mass. I get the why not part but still don’t get the why yet, a ton of extra mass for cool factor isn’t how Tesla rolls normally, they have always been the king of eliminating unnecessary. Goal of design is simplicity, efficiency and mass scale production. If even 1lb of steel saved per CT at 1 million CT that’s 1 million pounds of steel, not to mention better range/efficiency.

Those who do not understand importance of fraction of a penny can not make a dollar.

Whatever the reason it is THEIR reason. You can always decide that it is too heavy for you and buy an aluminum and steel body on frame truck. For me, the 3mm stainless is essential, for all of the reasons that Elon gave during the unveiling.

 

[HaulingAss]

Yes, I saw that and got a giggle but heavy doors could be unnecessary weight/mass. I get the why not part but still don’t get the why yet, a ton of extra mass for cool factor isn’t how Tesla rolls normally, they have always been the king of eliminating unnecessary. Goal of design is simplicity, efficiency and mass scale production. If even 1lb of steel saved per CT at 1 million CT that’s 1 million pounds of steel, not to mention better range/efficiency.

Those who do not understand importance of fraction of a penny can not make a dollar.

The doors of a vehicle add significant crash protection to the occupants, not only by preventing intrusion of other vehicles into the space occupied by your loved ones, but by backing up and supporting the crush resistance of the cabin space. Doors are not dead weight but an integral component of the cabin's strength. That's why the hinges and latches on all modern vehicles are many times stronger than actually required to function only as door hinges/latches.

The doors are only "unnecessary weight/mass" if you think it's not necessary to protect the well-being of your passengers (which are likely the same thing as your family). And that's true even if we assume bullets will not be one of the threats your family requires protection from. If you have ever paid a hospital bill, you may understand how the phrase "penny wise and pound foolish" could be applied to the decision to make a passenger door out of thin and soft sheet metal.

Some of the perspectives I read here cause me to worry about the trajectory of the human intellect.

 

[firsttruck]

It is obvious the body will be made of many pieces welded together. However I also have the question of why the doors need to be so heavy as they don’t really have really good interface with the body so structural strength added would be relatively minimum. In theory a good cross beam reienforcing the laches/hinges with a thin piece of same metal door skin would do but obviously there has to be reasons Tesla did it besides why not make the doors to be Level IIIA protection.

Yes, I saw that and got a giggle but heavy doors could be unnecessary weight/mass. I get the why not part but still don’t get the why yet, a ton of extra mass for cool factor isn’t how Tesla rolls normally, they have always been the king of eliminating unnecessary. Goal of design is simplicity, efficiency and mass scale production. If even 1lb of steel saved per CT at 1 million CT that’s 1 million pounds of steel, not to mention better range/efficiency.

Those who do not understand importance of fraction of a penny can not make a dollar.

A standard vehicle door structure is made of two separate layers of steel (exterior panel, raised interior panel), hinge reinforcement plates, latch/lock reinforcement plate, and body intrusion reinforcement beams and all this is welded together. Each steel layer might be 0.7mm to 0.9mm. The outer panel is high carbon steel while the intrusion reinforcement beam might be ultra high strength steel. So in the width dimension the door is two layers of steel (outer panel, interior frame) and in some places 3-4 layers with hollow space between most of the outer panel and interior frame. Within the steel structure hollow space are mounted the exterior handles, interior handles, window mechanism, latch, hinges, speakers, etc. The exterior panel is painted to match body while interior is covered with plastic trim cover panel.

The Cybertruck 3mm cold rolled stainless looks like it is excessive but it actually is doing the job of multiple components of a standard door while being stronger, less complex to build and probably overall be lighter. No body intrusion reinforcement beams and their welding. No reinforcement plates and welding. No interior steel frame. Some mechanisms will be anchored directly to the 3mm cold rolled stainless outer panel while other mounted to plastic inner panel. Plastic panel interior cover. With the Cybertruck all the steel is on the outside panel instead of the standard door which made mostly from thin mild steel formed into a tall & wide but narrow box.

8

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Body Structures - Made by MAGNA
https://www.magna.com/products/product/body-structures

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Advanced High Strength Steel (AHSS) for Stronger, Lighter and Safer Cars
By NS Nina Samodajev on June 3, 2019
https://matmatch.com/resources/blog/advanced-high-strength-steel-stronger-lighter-safer-cars/

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SMDI: More than 65 advanced high-strength steel vehicles debuted in 2018
By John Huetter on January 8, 2019
https://www.repairerdrivennews.com/...high-strength-steel-vehicles-debuted-in-2018/

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How It's Made - Car Doors
Discovery and Science Channel's How It's Made Car Doors episode.
2011
Panos Egglezos


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Robotic Car Door Manufacturing Line built by Machine Dynamics for Ford Australia
Sep 18, 2012
andrewdonalddesign


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[Qball]

Damn, that’s a long post!!! LOL

there are 3 contact points for a door and anything outside of that triangle won’t contribute much to over strength. It certain will be simpler to make with a single bent metal sheet and that’s probably the goal. My theory is use high strength steel for that triangle and weld/bolt the skin to the triangle. Most like that would save some weight but it also gives up the simplicity of a single metal sheet. traditional car doors are all looks like fenders and add very little to over all strength to the structure besides the crossbeam.

There are certainly lots of trade offs one way or the other and I suspect Elon is willing to sacrifice a little extra mass/cost for reduced manufacturing steps and time for faster production rate.

 

[Crissa]

there are 3 contact points for a door and anything outside of that triangle won’t contribute much to over strength.

...And the rest of the door can just cave in when hit in a collision?

-Crissa

 

[Qball]

The doors of a vehicle add significant crash protection to the occupants, not only by preventing intrusion of other vehicles into the space occupied by your loved ones, but by backing up and supporting the crush resistance of the cabin space. Doors are not dead weight but an integral component of the cabin's strength. That's why the hinges and latches on all modern vehicles are many times stronger than actually required to function only as door hinges/latches.

The doors are only "unnecessary weight/mass" if you think it's not necessary to protect the well-being of your passengers (which are likely the same thing as your family). And that's true even if we assume bullets will not be one of the threats your family requires protection from. If you have ever paid a hospital bill, you may understand how the phrase "penny wise and pound foolish" could be applied to the decision to make a passenger door out of thin and soft sheet metal.

Some of the perspectives I read here cause me to worry about the trajectory of the human intellect.

door are like fenders, vanity add on and keep out the weather and hold the window. Only thing protects you during a crash is the crossbeam. The whole point of sledge hammer to a normal door is to prove that very point. Indeed the trajectory of human intellect is falling off a cliff.

 

[Qball]

...And the rest of the door can just cave in when hit in a collision?

-Crissa

if the object misses the crossbeam then yes, it won’t do much. If a kick or a run away shopping cart can dent the skin then doubtful it would much during a high speed crash. My car doors have many dents and they certainly aren’t from crashes, just some people open their doors carelessly.

btw have you ever push your finger on a corvette door skin?

 

[Crissa]

if the object misses the crossbeam then yes, it won’t do much. If a kick or a run away shopping cart can dent the skin then doubtful it would much during a high speed crash. My car doors have many dents and they certainly aren’t from crashes, just some people open their doors carelessly.

...And that is relevant to the Cybertruck how?

-Crissa

 

[Qball]

...And that is relevant to the Cybertruck how?

-Crissa

Well, you asked what happens to a normal car door during a crash, it just caves in until the crossbeam. If there isn’t a cross beam then the door will keep on caving. The point is the crossbeam is structure/crash protection and rest is vanity/weather proofing.

CT can get away with crossbeam and skin also but Elon decided not to go that rout for reasons obviously. And I suspect the reason are less parts, less steps or faster production but take the penalty of weight.

 

[firsttruck]

...And the rest of the door can just cave in when hit in a collision?

if the object misses the crossbeam then yes, it won’t do much.

Exactly why 3mm cold-rolled stainless steel door instead of standard steel box structure door.

Every Cybertruck door will be full-size cross beam.

Cybertruck will be safest high volume pickup truck on the market.

 

[Qball]

Ok, further clarification:

doors are to keep weather out and passengers in.

doors are not structure or add rigidity to the car chassis at all

in Traditional doors the cross beams are there for crash protection and structural of the door but not structure the car/chassis

CT’s doors are no different and only provide crash protection but as demoed also good for hand gun protection

There isn’t a practical way for a door locking mechanism to provide enough force to add to chassis structural strength. Even the lowly anti-roll bars from yesterday years have to be bolted down as much as possible to provide a little extra chassis rigidity.

 

[Qball]

Every Cybertruck door will be full-size cross beam.

Cybertruck will be safest high volume pickup truck on the market.

Amen to that, even CT doors will be just as tough as semi trucks’ steel bumpers(3/8 mild steel?). Overkill? Absolutely!

the steel off-road bumper on my old Land Cruiser is only 1-1.5 mm mild steel and well above most passenger car cross beams, I can’t imagine what that thing would do to a compact or even full sized car doors in a crash. Very little chance my bumper would hit crossbeams even with today’s “SUVs”. Especially when fully loaded for a trip, truck stop scale said 6600lbs with me inside a normal door is like beer cans.

 

[HaulingAss]

Amen to that, even CT doors will be just as tough as semi trucks’ steel bumpers(3/8 mild steel?). Overkill? Absolutely!

the steel off-road bumper on my old Land Cruiser is only 1-1.5 mm mild steel and well above most passenger car cross beams, I can’t imagine what that thing would do to a compact or even full sized car doors in a crash. Very little chance my bumper would hit crossbeams even with today’s “SUVs”. Especially when fully loaded for a trip, truck stop scale said 6600lbs with me inside a normal door is like beer cans.

Semi-truck bumpers are not anywhere near 3/8" thick steel, that would be considered plate steel. More typically 10 gauge carbon sheet steel, slightly thicker than the Cybertruck's nearly 3mm thick exoskeleton. However, the cold-rolling will make the stainless steel of the Cybertruck exoskeleton stronger than the carbon steel semi-truck bumper.

Also, the high-strength steel crossbeams in most vehicle doors do not need to be impacted directly to be of great benefit. The crossbeam helps prevent the door from caving in when impacted, even if the main impact is above or below the crossbeam. Keep in mind that it's somewhat non-sensical to talk about a side impact that missed the door's crossbeam because the front of other vehicles are never shaped like a sharp wedge, at least not the structural parts of the front of the car. Will Cybertruck have a crossbeam inside its doors? It's probably not needed but we don't know yet. It could have a cross member in there if testing shows it to be a benefit.