Walk me through the design decision for the cybertruck

[daniel]

What makes you think there won't be a crumple zone or that it won't be safe in a crash?

As others have commented, the hard-rolled stainless steel body is supposed to be impervious to a sledgehammer strike. I'm not saying there won't be a crumple zone. There will be a crumple zone because Tesla has demonstrated its commitment to safety in all of its cars. I'm saying I'm interested to see how they achieve a crumple zone in a body that's impervious to sledgehammers.

 

[mongo]

As others have commented, the hard-rolled stainless steel body is supposed to be impervious to a sledgehammer strike. I'm not saying there won't be a crumple zone. There will be a crumple zone because Tesla has demonstrated its commitment to safety in all of its cars. I'm saying I'm interested to see how they achieve a crumple zone in a body that's impervious to sledgehammers.

Crumple zones are mostly in the front. Side impacts stops at the pack if the pole makes it past the HSS door beam (typical Tesla).

Triangle nose has less strength in the travel direction and the supporting stucture can be designed to give on impact. The bending of the front SS will dissipate a bunch of energy also. Might be more like a spring or damper than a crumple.

 

[daniel]

Crumple zones are mostly in the front. Side impacts stops at the pack if the pole makes it past the HSS door beam (typical Tesla).

Triangle nose has less strength in the travel direction and the supporting stucture can be designed to give on impact. The bending of the front SS will dissipate a bunch of energy also. Might be more like a spring or damper than a crumple.

It can't be a spring. To protect the passengers the car must absorb and dissipate energy, not receive it and throw it back. Tesla will make the car safe. I'm just interested in seeing how they do it. Stainless steel seems like a material not well suited to the task.

 

[Saghost]

As others have commented, the hard-rolled stainless steel body is supposed to be impervious to a sledgehammer strike. I'm not saying there won't be a crumple zone. There will be a crumple zone because Tesla has demonstrated its commitment to safety in all of its cars. I'm saying I'm interested to see how they achieve a crumple zone in a body that's impervious to sledgehammers.

A crash has a lot more force than a sledgehammer.

Usually the hardest crash to deal with is the small offset - the other car hits to the outside of the major structure and can slide right up the side and smack the passenger cell.

I think that’s why GM and Nissan created a virtual engine block in their EVs - the way they learned to solve small offset is to tie the sides together with a stiff heavy element, and drag the other side along as it crumples to absorb the energy.

So having the exoskeleton could be a big benefit for crashing - with it on the outside, small overlap is still hitting the major structure, and I bet they set up their frame geometry and attachment to cripple the exoskeleton locally under crash loads, with the center of the nose just stiff enough to transfer a crash into the side frames.

 

[Vinc]

A crash has a lot more force than a sledgehammer.

Usually the hardest crash to deal with is the small offset - the other car hits to the outside of the major structure and can slide right up the side and smack the passenger cell.

I think that’s why GM and Nissan created a virtual engine block in their EVs - the way they learned to solve small offset is to tie the sides together with a stiff heavy element, and drag the other side along as it crumples to absorb the energy.

So having the exoskeleton could be a big benefit for crashing - with it on the outside, small overlap is still hitting the major structure, and I bet they set up their frame geometry and attachment to cripple the exoskeleton locally under crash loads, with the center of the nose just stiff enough to transfer a crash into the side frames.

But this would also mean that there is more risk to damaging the frame and junking the truck even in relatively minor crashes, correct? Since the frame is the body panels, and those will have to do the work to absorb all the energy.

I am very curious to see how the plan on dealing with that, otherwise insurance costs will go through the roof. Will they just strip the damaged shell, move everything to a new shell and call it a day? Sounds a bit complicated.

 

[mspohr]

But this would also mean that there is more risk to damaging the frame and junking the truck even in relatively minor crashes, correct? Since the frame is the body panels, and those will have to do the work to absorb all the energy.

I am very curious to see how the plan on dealing with that, otherwise insurance costs will go through the roof. Will they just strip the damaged shell, move everything to a new shell and call it a day? Sounds a bit complicated.

You're making it too complicated.
There is no frame.
Cut and paste the crumpled panels.

 

[Vinc]

You're making it too complicated.
There is no frame.
Cut and paste the crumpled panels.

Probably yes, I am overthinking. And I am by no means an expert. But my understanding is that patching estructural elements (yes, no frame, but the exoskeleton is an estructural element one way or another) is not as straightforward as it might seem. For one, the welding points may not be as strong as the rest of the structure, and they can snap should another crash happen.

But I insist, I don't fully know what I am talking about

 

[mspohr]

Probably yes, I am overthinking. And I am by no means an expert. But my understanding is that patching estructural elements (yes, no frame, but the exoskeleton is an estructural element one way or another) is not as straightforward as it might seem. For one, the welding points may not be as strong as the rest of the structure, and they can snap should another crash happen.

But I insist, I don't fully know what I am talking about

I too, don't know what I'm talking about but it seems that when you have a frame, it can get bent and then is difficult to repair. If you have a exoskeleton structure, it seems to me that you can just cut out the damaged parts and weld in new pieces.
Think of a honeycomb. If it gets damaged, it doesn't distort the whole structure, just crumples the damaged part. It's easy to piece in a new section of honeycomb.

 

[bedoig]

I too, don't know what I'm talking about but it seems that when you have a frame, it can get bent and then is difficult to repair. If you have a exoskeleton structure, it seems to me that you can just cut out the damaged parts and weld in new pieces.
Think of a honeycomb. If it gets damaged, it doesn't distort the whole structure, just crumples the damaged part. It's easy to piece in a new section of honeycomb.

I don't know, sounds like a sticky situation.

 

[MichaelP90DL]

It can't be a spring. To protect the passengers the car must absorb and dissipate energy, not receive it and throw it back. Tesla will make the car safe. I'm just interested in seeing how they do it. Stainless steel seems like a material not well suited to the task.

What are the crash requirements for a BIG truck, such as a semi? Do they have crumple zones? If it's different from a car, maybe Tesla scaled down whatever semis use to the Cybertruck. Just wondering.

 

[Saghost]

But this would also mean that there is more risk to damaging the frame and junking the truck even in relatively minor crashes, correct? Since the frame is the body panels, and those will have to do the work to absorb all the energy.

I am very curious to see how the plan on dealing with that, otherwise insurance costs will go through the roof. Will they just strip the damaged shell, move everything to a new shell and call it a day? Sounds a bit complicated.

It’ll be interesting to see. It might be a simple unbolt and replace situation, or it might be really messy. It depends on the details of how they designed and attached the elements.

How much they were able to force crippling failures is important, too - that’ll determine how widespread the damage is beyond the impact point.

Those stiff, tough stainless steels don’t like to bend, so simply bending crumpled sections back into shape isn’t going to be easy, and may not work at all.

 

[Dazureus]

I too, don't know what I'm talking about but it seems that when you have a frame, it can get bent and then is difficult to repair. If you have a exoskeleton structure, it seems to me that you can just cut out the damaged parts and weld in new pieces.
Think of a honeycomb. If it gets damaged, it doesn't distort the whole structure, just crumples the damaged part. It's easy to piece in a new section of honeycomb.

I'm not a mechanical engineer but I had a few materials courses for my engineering degree. You're right about having a frame. If there'a a minor crash, then maybe just the panel or bumper gets damaged (plus some surrounding trim) and those can be removed and replaced. If there's a larger crash, some of the frame may get bent. Insurance will determine if the cost to straighten the frame will be worth the repair or totaling it.

For the Cybertruck, as I understand it and mentioned here, the exterior is the structure. If the crash is great enough to distort the panel then it would need to be replaced. What is the unknown factor is how this will be done. If the entire length of the vehicle is one piece, I worry that the whole thing would need to be replaced. Since the panel is cold rolled, cutting and welding the panel might introduce weak spots where the welding temps weaken the steel in the heat affected zone. There aren't any apparent seams in the side of the truck. They may be hidden in the door frame area and if so, the vehicle could be divided into sectors that could be replaced for repair. What's missing is how those panels connect together; since there's no frame, they can't bolt to something except the next panel. However it's done, I don't think it will be possible to just cut out sections to replace with welding, especially if Tesla has some kind of planned failure crumple area.

 

[Electruck]

First, you open an automotive assembly factory, and learn A LOT.

Second, you figure out how to eliminate MOST of the body shop and paint shop.

Third, BladeRunner 2049 is premiering, go take a break you've earned it.

Lastly, listen to what the CORE of truck owners want by listening to Off-roaders and Contractors.

GO!!!

 

[mongo]

It can't be a spring. To protect the passengers the car must absorb and dissipate energy, not receive it and throw it back. Tesla will make the car safe. I'm just interested in seeing how they do it. Stainless steel seems like a material not well suited to the task.

Spring was a bad choice of words, meant hinge/ accordian, though there will be some spring back. The stainless is hard the bend, so the impact will dissipate a lot of energy bending it. The whole system might work out quite well since the initial bend takes more force, and energy is the square of speed. So more effort is needed at the start to achieve a constant deceleration.