5 ms·

The Appian Way does not permit heavy trucks. Road damage increases to fourth power of vehicle weight. https://en.wikipedia.org/wiki/Fourth_power_law https://en.

by pushcx 3y ago

The Appian Way does not permit heavy trucks. Road damage increases to fourth power of vehicle weight. https://en.wikipedia.org/wiki/Fourth_power_law https://en.wikipedia.org/wiki/Fourth_power_law

queuebert 3y ago
That is an amazing empirical fact. As a physicist, my mind goes to something like the acceleration of the acceleration (jounce), but I can't find a model for what is being observed.
- ndriscoll 3y ago
  I know next to zero material science, but I would think there's not much motion going on, and that it's more that once you're past the yield strength, stress causes nonlinear increases in strain, and you get hysteresis (i.e. permanent deformations). Then over time those deformations add up to a weaker structure that eventually fractures. As long as you stay within or close to the linear regime, there's little to no permanent damage. I imagine it's more of a chemical process (i.e. you're damaging the bonds/lattice structure of a material), but I don't know.
- Balgair 3y ago
  > the acceleration of the acceleration (jounce) Amazing. I had always learned it as the snap. Learn something new every day https://en.wikipedia.org/wiki/Fourth,_fifth,_and_sixth_derivatives_of_position https://en.wikipedia.org/wiki/Fourth,_fifth,_and_sixth_deriv...
lifestyleguru 3y ago
Increasing every vehicle weight by over 500kg by adding batteries, increases the road wear by... at least 4 times for a subcompact.
- hinkley 3y ago
  I haven't been seeing electric vehicles weighing 500kg more. Closer to 500lbs more. Offset by the drivetrain. Increasing vehicle weight by about 15% would be 75% more damage per passenger vehicle. Which is not nothing, but for comparison, those 5000 pound trucks are doing almost 8 times as much road damage as a midsized sedan by weighing 2/3 more. But let's say you're right and the sedans weigh 30% more instead of 15% more, then it's about 2.8x the damage of an ICE. Trucks are still doing more damage than 3 battery electric vehicles. Honestly the weight of these things needs to come down over time. But you need infrastructure to do that. Lighter batteries don't just materialize out of thin air. Getting battery weight down increases range. Which can either make a car with better range, or let you shrink the battery another 5%.
  - lifestyleguru 3y ago
    Last fully IC Honda Civic or Toyota Corolla is 1300 kg, Tesla 3 is 1800 kg. That's over 3.5 times more road wear.
    - hinkley 3y ago
      That's a bullshit comparison, and if I recall correctly, people dog-piled on you for making that exact same comparison a couple months ago. If that's you, get a new comparison. If not, I don't want to have this discussion a second time. You can't compare a Tesla to a Honda. They're in a different customer class. Try an Acura at least. Even a Jetta only weighs 400kg less than a Tesla 3, and that's still a down-market car. Luxury cars are heavier.
      - lifestyleguru 3y ago
        Don't have Acura in Europe ¯\_(ツ)_/¯
- thomastjeffery 3y ago
  Yes, but that's nothing compared to the 3,000 times more damage that a semi-truck hauling your groceries does.
Balgair 3y ago
I'm trying to model in my head as to why that would be the case, but I'm not coming up with much. Does anyone have any insights? Also, another hypercube law: Neuron firing rates go as temperature to the 4th power. So, a small change in temperature increase the number of firings per second drastically. This is due to the speed at which charges can move in and out of the neuron, which going though a lot of math and fun modeling, ends up being related to the Stefan–Boltzmann law of black-body radiation. Anyone else got fun hypercube+ laws that they know?

by pushcx 3y ago

The Appian Way does not permit heavy trucks. Road damage increases to fourth power of vehicle weight. https://en.wikipedia.org/wiki/Fourth_power_law https://en.wikipedia.org/wiki/Fourth_power_law

queuebert 3y ago

That is an amazing empirical fact. As a physicist, my mind goes to something like the acceleration of the acceleration (jounce), but I can't find a model for what is being observed.

ndriscoll 3y ago
I know next to zero material science, but I would think there's not much motion going on, and that it's more that once you're past the yield strength, stress causes nonlinear increases in strain, and you get hysteresis (i.e. permanent deformations). Then over time those deformations add up to a weaker structure that eventually fractures. As long as you stay within or close to the linear regime, there's little to no permanent damage. I imagine it's more of a chemical process (i.e. you're damaging the bonds/lattice structure of a material), but I don't know.
Balgair 3y ago
> the acceleration of the acceleration (jounce) Amazing. I had always learned it as the snap. Learn something new every day https://en.wikipedia.org/wiki/Fourth,_fifth,_and_sixth_derivatives_of_position https://en.wikipedia.org/wiki/Fourth,_fifth,_and_sixth_deriv...

lifestyleguru 3y ago

Increasing every vehicle weight by over 500kg by adding batteries, increases the road wear by... at least 4 times for a subcompact.

hinkley 3y ago
I haven't been seeing electric vehicles weighing 500kg more. Closer to 500lbs more. Offset by the drivetrain. Increasing vehicle weight by about 15% would be 75% more damage per passenger vehicle. Which is not nothing, but for comparison, those 5000 pound trucks are doing almost 8 times as much road damage as a midsized sedan by weighing 2/3 more. But let's say you're right and the sedans weigh 30% more instead of 15% more, then it's about 2.8x the damage of an ICE. Trucks are still doing more damage than 3 battery electric vehicles. Honestly the weight of these things needs to come down over time. But you need infrastructure to do that. Lighter batteries don't just materialize out of thin air. Getting battery weight down increases range. Which can either make a car with better range, or let you shrink the battery another 5%.
- lifestyleguru 3y ago
  Last fully IC Honda Civic or Toyota Corolla is 1300 kg, Tesla 3 is 1800 kg. That's over 3.5 times more road wear.
  - hinkley 3y ago
    That's a bullshit comparison, and if I recall correctly, people dog-piled on you for making that exact same comparison a couple months ago. If that's you, get a new comparison. If not, I don't want to have this discussion a second time. You can't compare a Tesla to a Honda. They're in a different customer class. Try an Acura at least. Even a Jetta only weighs 400kg less than a Tesla 3, and that's still a down-market car. Luxury cars are heavier.
    - lifestyleguru 3y ago
      Don't have Acura in Europe ¯\_(ツ)_/¯
thomastjeffery 3y ago
Yes, but that's nothing compared to the 3,000 times more damage that a semi-truck hauling your groceries does.

Balgair 3y ago

I'm trying to model in my head as to why that would be the case, but I'm not coming up with much. Does anyone have any insights? Also, another hypercube law: Neuron firing rates go as temperature to the 4th power. So, a small change in temperature increase the number of firings per second drastically. This is due to the speed at which charges can move in and out of the neuron, which going though a lot of math and fun modeling, ends up being related to the Stefan–Boltzmann law of black-body radiation. Anyone else got fun hypercube+ laws that they know?