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Oapfu
Oapfu GRM+ Memberand Reader
2/18/24 8:53 p.m.

I think I made the forum software mad by replying to the same thread in two different browser tabs.

I can retype the long versions if anyone cares, otherwise the short versions:

gencollon's estimate about the tires receiving 20% as much energy as the brakes could be pretty close.  Highschool-level physics suggests it is about the same as the tire slip ratio, and a tire's max coefficient of friction typically happens at a slip ratio of 0.15-0.20

Bing's 962 hp for braking power seems really high.  Based on simple motion formulas and initial kinetic energy at 60 mph, I get 358hp.  I can match Bing's numbers for time and acceleration.  Kinetic energy is ~548kJ, dumping that in 2.05s = 267kW or 358HP.  That's low b/c I didn't include any spinning things like wheels/tires.  OTOH, dumping it at a rate of 962 HP should take 0.76 s.

ProDarwin
ProDarwin MegaDork
2/18/24 10:47 p.m.
aircooled said:

That's an interesting concept.  How much "horsepower" do the brakes generate stopping a car?  Pretty easy to calculate (I think) with just the distance and the weight of the car.

The maximum theoretical average power required to stop the corvette from 60 to 0, assuming 100% of the energy flows to the brakes is super easy to calculate.  A 1524kg Corvette traveling at 60mph has 547kj of kinetic energy.  Dissipating 547kj in 2.5 seconds is equal to 219kw or 293hp.  There is no way the brakes can do more work than that, however they can do less.

That said, that is average power, which is misleading.   The higher the speed, the more brake power required to generate that same level of deceleration - 293hp is NOT going to generate the required deceleration at 60mph, but it will be overkill at 5mph.

Super simple graph (forgive me, on a computer without excel, so I used google sheets which is... eh)

The power required to decel at 1.33g at 60 mph (~27m/s) is around 530kw or 710hp at the most.

I'm too lazy at the moment to factor in other stuff, but wind resistance and rolling is easily calculated and will reduce the number by ~15hp (shooting from the hip on this one, but imagine the power required to cruise at 60mph).

Engine braking can be a significant contributor as well.

 

 

No, wheel diameter doesn't come into play.

 

This stuff is actually pretty straightforward math, so I would think its more suited to direct programming instead of artificial intelligence which is trained as more of a replacement for human cognitive functions, right?

ProDarwin
ProDarwin MegaDork
2/18/24 10:58 p.m.

And just to back up Codrus's point earlier, lets bump the scale to something that may replicate speeds a Corvette might see.

80m/s is about 180mph.  The power required from the brakes to generate 1.33g at that speed would be 2,130 hp.  That said, the wind resistance at that speed is going to be significant, but even if you factor in that in, you are left with probably something like 1500hp required.

ProDarwin
ProDarwin MegaDork
2/18/24 11:00 p.m.

Edit:  I made another post too and its messing up.  Not sure whats up with the forum software here, but its buggy as hell in this thread

 

edit:  oh I can see it from my phone though.  Cache problem? 

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