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Comment by willmadden | Hacker News Reader

I don't think there's a problem with cable weight with electric motors. Production EV's today have ridiculous amounts of torque and don't require prohibitively heavy cables.

The issue with acceleration using wheels is gravity. You are limited to 1g, the downforce on the wheels, which you use for traction to push the vehicle forward. Spoilers increase the downforce on the vehicle beyond 1g, but the energy required to do that is proportional to the drag on the spoiler.

Short of a rocket engine, the way to accelerate beyond 1g with a wheeled vehicle is to have a downforce fan. That can be powered by combustion or by electricity. I don't know which would offer the highest power to weight ratio.

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> Short of a rocket engine, the way to accelerate beyond 1g with a wheeled vehicle is to have a downforce fan.

This electric vehicle is accelerating to 100kph (~28 m/s) in less than 1.5 seconds, which is an average acceleration of about 2g, if I am not mistaken.

Looking around, I have seen 4.0 given as a representative friction coefficient for drag racing tires, which would imply a corresponding peak acceleration of 4g without aerodynamic assistance (again, if I am not mistaken.)

BEV used to have around 80kg of copper [1], nowadays, manufacturers are moving towards 800V architecture attempting to cut the weight in half.

I also feel like 800V cars also maintain their maximum power better on lower SoC than 400V systems.

[1] https://www.copper.org/publications/pub_list/pdf/A6192_Elect...

If we are already what-if-ing with wired power delivery, just skip the pantograph and look at what wire-guided missiles do: they have their data lines on a spool, unrolling as they go. For power you certainly wasn't thicker wires, and while you're at it, you'll certainly power the unrolling of the spool instead of just dragging it to spin up. Then if the spool unrolling is for some reason faster than the wheels, the wire will serve as reaction mass, pushing the vehicle. Now we have what's essentially a copper rocket that isn't constrained by downforce and tire grip at all.

I’m not sure having a ‘reverse Helicopter’ on the back of your vehicle really qualifies as ‘ground vehicle’ at that point. Especially if it’s providing enough force to literally drive upside down on a ceiling somewhere.

it's as ground as can be, short of a tunneling machine maybe.

This was the basis of a very famous F1 car in the 1970s. It was ultimately banned.

What's the down force for an F1 car? Are they not ground vehicles?

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