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Well if the outer layer does not deform that's not generally bad, no? It could still crumple behind that and the structure could move like scales when hit on th

Well if the outer layer does not deform that's not generally bad, no? It could still crumple behind that and the structure could move like scales when hit on the edges. I'd guess it depends a lot on whats underneath, after all it's not an exo-sceleton (or is it?). edit: thanks for the replies. I somehow thought if you get hit as a pedestrian it's super bad anyways... didn't know the crumple zone does much for you there.

ThePhysicist 7y ago
It’s relatively easy to make a car exterior that won’t crumple in an accident, the reason cars don’t have that is that the inelastic deformation of the car structure absorbs quite a lot of energy during an impact, which would otherwise be transferred to the vehicle in form of kinetic energy. You might say a little energy difference is not important but for a passenger or a pedestrian / cyclist hit by the car it can be the difference between suffering light bruises and dying from the impact. When I saw Tesla’s design with the ultra hard steel and sharp edges I immediately thought this thing is a large danger to other people on the street, especially cyclists and pedestrians.
yreg 7y ago
>if the outer layer does not deform that's not generally bad, no? it is generally very bad for the person who gets hit by the car
- henkslaaf 7y ago
  It's also bad for people in the car.
- kinghajj 7y ago
  Does it make much difference if a car can crumple or not when it's hitting a sack of flesh? I don't think my skin and bones are going to stand up well in either scenario.
  - zwaps 7y ago
    Honestly, have you seen a rigid car hitting a crumply car going full force? In a situation where maybe both would have survived otherwise, now at least one party is goo. It's a Prisoner's Dilemma. If everyone drives fat, rigid SUVs, I gotta do to. That's why there is a law
    - viraptor 7y ago
      I'm not sure this is comparable. The question is, does the crumbling matter against a person not in another car. I've seen small super-brittle cars not being damaged at all by a collision with a pedestrian. Ncap includes these tests and it seems they're more interested in flexibility in that case, not in crumbling.
    - ZeroGravitas 7y ago
      I agree, but you can also crash into concrete walls and bollards where you'd want a crumple zone. A crumple zone in an EV is pretty simple though, since you don't have to worry about the heavy engine getting shoved into the front passengers. I'm not sure why it's such a popular notion that the cybertruck won't crumple? It's literally got a big empty space at the front as a feature. Ordinary cars crumple but they don't fall apart if you lean on them or drive down a bumpy road. They have strength in some situations and specially designed failure modes in others. It could be as simple as putting some scores in the metal so that it folds in a particular way when sufficient force is applied.
      - masklinn 7y ago
        > I'm not sure why it's such a popular notion that the cybertruck won't crumple? It's literally got a big empty space at the front as a feature. Because it's supposed to be bulletproof and have a virtually indestructible surface which you cannot dent or scratch. It's possible that this was meant as nothing more than resistance to minor assault but taking the statement literally and assuming a completely rigid reinforced frame makes a lot of sense. > Ordinary cars crumple but they don't fall apart if you lean on them or drive down a bumpy road. Ordinary cars are not billed as bulletproof and virtually indestructible.
masklinn 7y ago
> Well if the outer layer does not deform that's not generally bad, no? Yes it is. Crumple zones are designed to both avoid going straight through through whatever they hit (which is usually an other car, though avoiding pasting pedestrian is also a good idea if you can), and disperse the energy of the collision to provide progressive deceleration. Rigid frames are the original state of cars design, and it was bad, because when the car does not absorb the impact and progressively decelerate (again thanks to crumple zones) all the force of the crash ends up with the vehicle's occupants. Which is the exact opposite of what you're looking for: you want to sacrifice what's outside the safety cell in order to limit or nullify damage inside the safety cell (companies are even working on "sledding" the survival cell and adding dedicated shock absorbers, especially in smaller city cars where there isn't much space for crumple zones to do their work)./

ThePhysicist 7y ago

It’s relatively easy to make a car exterior that won’t crumple in an accident, the reason cars don’t have that is that the inelastic deformation of the car structure absorbs quite a lot of energy during an impact, which would otherwise be transferred to the vehicle in form of kinetic energy. You might say a little energy difference is not important but for a passenger or a pedestrian / cyclist hit by the car it can be the difference between suffering light bruises and dying from the impact. When I saw Tesla’s design with the ultra hard steel and sharp edges I immediately thought this thing is a large danger to other people on the street, especially cyclists and pedestrians.

yreg 7y ago

>if the outer layer does not deform that's not generally bad, no? it is generally very bad for the person who gets hit by the car

henkslaaf 7y ago
It's also bad for people in the car.
kinghajj 7y ago
Does it make much difference if a car can crumple or not when it's hitting a sack of flesh? I don't think my skin and bones are going to stand up well in either scenario.
- zwaps 7y ago
  Honestly, have you seen a rigid car hitting a crumply car going full force? In a situation where maybe both would have survived otherwise, now at least one party is goo. It's a Prisoner's Dilemma. If everyone drives fat, rigid SUVs, I gotta do to. That's why there is a law
  - viraptor 7y ago
    I'm not sure this is comparable. The question is, does the crumbling matter against a person not in another car. I've seen small super-brittle cars not being damaged at all by a collision with a pedestrian. Ncap includes these tests and it seems they're more interested in flexibility in that case, not in crumbling.
  - ZeroGravitas 7y ago
    I agree, but you can also crash into concrete walls and bollards where you'd want a crumple zone. A crumple zone in an EV is pretty simple though, since you don't have to worry about the heavy engine getting shoved into the front passengers. I'm not sure why it's such a popular notion that the cybertruck won't crumple? It's literally got a big empty space at the front as a feature. Ordinary cars crumple but they don't fall apart if you lean on them or drive down a bumpy road. They have strength in some situations and specially designed failure modes in others. It could be as simple as putting some scores in the metal so that it folds in a particular way when sufficient force is applied.
    - masklinn 7y ago
      > I'm not sure why it's such a popular notion that the cybertruck won't crumple? It's literally got a big empty space at the front as a feature. Because it's supposed to be bulletproof and have a virtually indestructible surface which you cannot dent or scratch. It's possible that this was meant as nothing more than resistance to minor assault but taking the statement literally and assuming a completely rigid reinforced frame makes a lot of sense. > Ordinary cars crumple but they don't fall apart if you lean on them or drive down a bumpy road. Ordinary cars are not billed as bulletproof and virtually indestructible.

masklinn 7y ago

> Well if the outer layer does not deform that's not generally bad, no? Yes it is. Crumple zones are designed to both avoid going straight through through whatever they hit (which is usually an other car, though avoiding pasting pedestrian is also a good idea if you can), and disperse the energy of the collision to provide progressive deceleration. Rigid frames are the original state of cars design, and it was bad, because when the car does not absorb the impact and progressively decelerate (again thanks to crumple zones) all the force of the crash ends up with the vehicle's occupants. Which is the exact opposite of what you're looking for: you want to sacrifice what's outside the safety cell in order to limit or nullify damage inside the safety cell (companies are even working on "sledding" the survival cell and adding dedicated shock absorbers, especially in smaller city cars where there isn't much space for crumple zones to do their work)./