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We have a tunnel nearby that was built with a grade that’s too steep. Every year there’s a large ICE truck that overheats, catches fire and shuts the tunnel dow

by audunw 1y ago

We have a tunnel nearby that was built with a grade that’s too steep. Every year there’s a large ICE truck that overheats, catches fire and shuts the tunnel down for a while. This is simply not going to be an issue with EV trucks. A fire is possible but much less likely in general, and MUCH less likely in that specific scenario. In Norway we’ve also already seen that tunnels and garages require less ventilation as the share of EVs gets higher, saving millions on new construction. Electric semi trucks will unlock the full benefit. Larger vehicles like trucks and buses is also where you get the most benefit of noise reduction. EV semi trucks are going to improve so many things.

ralferoo 1y ago
> This is simply not going to be an issue with EV trucks. A fire is possible but much less likely in general, and MUCH less likely in that specific scenario. I'm actually not so sure. If the gradient is so steep that the vehicle is struggling to move at all, the current through the motor windings will be very high, causing the windings to overheat, potentially fail and potentially short circuit. There's a high risk of damaging the MOSFETs in the motor controller, which very much could lead to a fire risk depending on the failure mode. There's not really many ways to solve this problem - in a normal 3-phase winding, all you can do is remove the current until it cools down and try again, but that will force the motor to stop and then try to restart, so creating an even larger load. Possibly if you have 6 more more phases and more magnets such that each of the normal 3-phases has multiple windings and magnets, you can cycle through the different ones and still keep applying some torque, but obviously this would still not really solve the fundamental problem. Essentially the problem is the same for ICE vs EV - if the gradient is so steep and load so heavy that the engine / motor can't provide enough force, then it will be overloaded. Whether that's through pressure / shearing / excess heat in an ICE or through excess current / excess heat in EV, the outcome is failure to continue forward at best. The only real solution is to massively over engineer the engine for normal situations, but human nature being what it is, there will always push things way beyond the designed limits and safety margins until it fails.
- Kon5ole 1y ago
  >I'm actually not so sure. If the gradient is so steep that the vehicle is struggling to move at all The problem isn't overloading the engine when you go up, it's overheating the brakes when you go down. The reasoning here is probably that EV semis will use regeneration for some of the braking thus avoiding the overheating to some extent.
  - xienze 1y ago
    To be fair, the parent didn’t specify which direction they were talking about. And is brake overheating a cause for an entire truck to catch on fire? That sounds more like an engine failure kind of thing.
    - diggan 1y ago
      If I were to guess, it's about using "motor breaking" (not sure that's the correct English term for it) that you do if you travel downwards for a long time, in order to avoid over-heating the brakes so they are ineffective. I'm guessing doing motor breaking for too long, in a hot environment, might overheat the engine as well?
      - Symbiote 1y ago
        In Britain we call it "engine braking", I think Americans say the same. A quick search says it heats the engine less than accelerating, so shouldn't cause overheating.
      - gmueckl 1y ago
        I don't see how that could overheat the engine. You're backdriving the engine from the wheels and fuel injection should be complete shit down so there is no combustion.
      - mikestew 1y ago
        Engine braking doesn’t work on diesels, that’s why they have “Jake brakes”, that loud braaaaaaaaap you hear when they go downhill (and why you see signs at the edge of town saying “compression brake use illegal”). I highly doubt a diesel engine would overheat going downhill. (Not a diesel mechanic, but FWIW used to be an auto mechanic decades ago.) https://en.wikipedia.org/wiki/Compression_release_engine_brake#Function https://en.wikipedia.org/wiki/Compression_release_engine_bra...

by audunw 1y ago

ralferoo 1y ago

> This is simply not going to be an issue with EV trucks. A fire is possible but much less likely in general, and MUCH less likely in that specific scenario. I'm actually not so sure. If the gradient is so steep that the vehicle is struggling to move at all, the current through the motor windings will be very high, causing the windings to overheat, potentially fail and potentially short circuit. There's a high risk of damaging the MOSFETs in the motor controller, which very much could lead to a fire risk depending on the failure mode. There's not really many ways to solve this problem - in a normal 3-phase winding, all you can do is remove the current until it cools down and try again, but that will force the motor to stop and then try to restart, so creating an even larger load. Possibly if you have 6 more more phases and more magnets such that each of the normal 3-phases has multiple windings and magnets, you can cycle through the different ones and still keep applying some torque, but obviously this would still not really solve the fundamental problem. Essentially the problem is the same for ICE vs EV - if the gradient is so steep and load so heavy that the engine / motor can't provide enough force, then it will be overloaded. Whether that's through pressure / shearing / excess heat in an ICE or through excess current / excess heat in EV, the outcome is failure to continue forward at best. The only real solution is to massively over engineer the engine for normal situations, but human nature being what it is, there will always push things way beyond the designed limits and safety margins until it fails.

Kon5ole 1y ago
>I'm actually not so sure. If the gradient is so steep that the vehicle is struggling to move at all The problem isn't overloading the engine when you go up, it's overheating the brakes when you go down. The reasoning here is probably that EV semis will use regeneration for some of the braking thus avoiding the overheating to some extent.
- xienze 1y ago
  To be fair, the parent didn’t specify which direction they were talking about. And is brake overheating a cause for an entire truck to catch on fire? That sounds more like an engine failure kind of thing.
  - diggan 1y ago
    If I were to guess, it's about using "motor breaking" (not sure that's the correct English term for it) that you do if you travel downwards for a long time, in order to avoid over-heating the brakes so they are ineffective. I'm guessing doing motor breaking for too long, in a hot environment, might overheat the engine as well?
    - Symbiote 1y ago
      In Britain we call it "engine braking", I think Americans say the same. A quick search says it heats the engine less than accelerating, so shouldn't cause overheating.
    - gmueckl 1y ago
      I don't see how that could overheat the engine. You're backdriving the engine from the wheels and fuel injection should be complete shit down so there is no combustion.
    - mikestew 1y ago
      Engine braking doesn’t work on diesels, that’s why they have “Jake brakes”, that loud braaaaaaaaap you hear when they go downhill (and why you see signs at the edge of town saying “compression brake use illegal”). I highly doubt a diesel engine would overheat going downhill. (Not a diesel mechanic, but FWIW used to be an auto mechanic decades ago.) https://en.wikipedia.org/wiki/Compression_release_engine_brake#Function https://en.wikipedia.org/wiki/Compression_release_engine_bra...