5 ms·
That is also the purpose of the wing on the back of the car. To generate more downwards force at speed.
by btilly 4y ago
That is also the purpose of the wing on the back of the car. To generate more downwards force at speed.
- jeffbee 4y agoRight, but the wing doesn't start to work until you hit serious speeds, whereas the fan gives the car extreme traction at launch, which is pretty important in a race that only lasts 30 seconds, especially when your electric car has ~infinite torque.
- ht85 4y agoAero also has the issue of creating a ton of drag. An f1 at 300kph will decelerate around 1g if you lift off the throttle.
- jeffbee 4y agoDid you see Pastrana's ridiculous Subaru with active aero? It puts the wings away when they're dragging and they pop back up when the downforce and/or drag is wanted.
- ht85 4y agoThanks for this, I had just seen a couple highlights, just watched it and it is absolutely ridiculous. Amazing :D
- jackmott42 4y agoThe wing starts to work immediately. Just not much. This is a pedantic but important point. Even low speed motoring events aero can be very very important if sufficiently large wings are allowed. Aerodynamic gear for cyclists is advantageous even if you are a slow cyclist, etc.
- loeg 4y agoPopular "wisdom" in cycling is that aerodynamics are not a factor below 10 mph and not much of one at 15. It becomes pretty noticeable in the 15-20+ mph range (increasing with the cube of speed, or something like that).
- jackmott42 4y agoYes, but the physics is that the amount time saved over a fixed distance is actually more for the 15mph cyclist than the 20mph cyclist. However the percent of time saved for the slower cyclist is less, but only a little. Basically at cycling speeds the aerodynamic curve is pretty flat so it doesn't really matter if you are fast or slow.
- binbag 4y agoInfinite torque...?
- B1FF_PSUVM 4y agoProbably thinking of https://en.wikipedia.org/wiki/Jerk_(physics) https://en.wikipedia.org/wiki/Jerk_(physics) If acceleration were an instantaneous off-on step, that would be a https://en.wikipedia.org/wiki/Dirac_delta_function https://en.wikipedia.org/wiki/Dirac_delta_function
- jeffbee 4y ago~ much more torque than can practically be delivered between the tires and the ground, which is why using a vacuum to improve the traction and eliminate the transient squatting motion of the vehicle is so important in a short race. Drag racers have had this problem for a long time; those races last less than 5 seconds. This hill climb is interesting because it's only a bit longer, half a minute, which really changes the equations for electric race cars vs. something like Pikes Peak which is 8 minutes to the top (and is now also totally dominated by electric cars).
- mywittyname 4y agoThis is a weird car guy myth that gets tossed around. The thinking is that, electric motors make uniform power output at any RPM, and torque = some_constant * power_output / RPM. Thus, as RPM goes to zero, torque goes to infinity. Obviously, this is wrong in the real world for so many reasons, but that doesn't stop this from getting repeated.
- throwaway0a5e 4y agoRepeating it is a great way to paint yourself as one of those dolts that likes to act like they care about EVs for the virtue points. Everyone who's ever used a drill knows that while speed and torque are inversely related in most of a motors normal operating range you don't get insane torque at low speed. Of course you can wind a motor differently to mitigate this somewhat but still, not a huge improvement. You wouldn't see reduction gears on all sorts of things if this were the case.
- jjav 4y ago> the wing doesn't start to work until you hit serious speeds I don't know what you consider "serious speeds", but wings can produce meaningful downforce at pretty low speeds. Check out the various unlimited class autocross cars which carry giants wings for downforce, even though autocross events are typically very low speed events (2nd gear most of the time).
- mywittyname 4y ago"Meaningful" on order of 100lbs at 60mph. Which isn't nothing, but a Viper ACR has a peak downforce of 2000lbs@177MPH, or basically half the total weight of the car. Plus, with extreme aero, there's a top-speed vs downforce tradeoff to be made. The big fan trick doesn't have that issue.
- giobox 4y agoIf you drill into published specs for wings, it's generally true they only really start to work at silly speeds on most road legal cars. The far more important effect is upon the emotional response of the owner when they look at it... There are exceptions, but virtually all rear spoilers only start to do their work meaningfully at well over 100mph. Example: Porche Cayman GT4 RS, extremely potent track-day Porche with giant wing. > https://newsroom.porsche.com/en/press-kits/718-spyder-cayman-gt4/aerodynamik.html https://newsroom.porsche.com/en/press-kits/718-spyder-cayman... > "At the car’s maximum speed, there is a total of 122 kg of rear downforce." Yes, thats right, you get 122kg of extra downforce once you hit 196mph. Really helpful in 2nd gear... The reason manufacturers generally only quote wing downforce on road cars at incredible speeds is because the number is not very impressive at lower ones.
- denimnerd42 4y agothat's a street car though. what about actual GT3 cup cars or GTD class cars? i couldn't find any numbers, but they do put them in the wind tunnel.
- jjav 4y ago> Example: Porche Cayman GT4 RS That's a street car. You need to look at race cars to see where wing development can go. For an example of race cars which generate downforce at autocross speeds, take a look at cars like https://www.autoxandtrack.com/a-mod-acme-special-fastest-autocross-car/ https://www.autoxandtrack.com/a-mod-acme-special-fastest-aut...
- omginternets 4y agoThe main issue is more so that they produce incredible downforce at the cost of incredible drag.