Full transcript of “Wings and Spoilers; Lift and Drag | How It Works”. Click a timestamp to open the video at that moment. Need another video? Use the YouTube transcript generator.
0:00 Bricks Teslas Splitters Wings - Spoiler alert, we're talking about aerodynamics (electronic music) There are sleek cars and boxy cars There's weird things sticking out of race cars and rice cars and they're all trying to take advantage of aerodynamics Aerodynamics is the study of how gases interact with moving objects. The two basic aerodynamics forces are drag and lift Drag is the force air exerts against a car as it moves, while lift is the perpendicular force exerted by the air on the car. Lift includes both positive lift that's the flying kind and negative lift and that's down force. Air moves in a very similar way to liquid,
0:47 you just can't see it. If you think about it, every time you drive, you're practically swimming through an endless air ocean Air obviously isn't as dense as liquid, but it's still touching stuff. So there's friction when something moves through it and that makes drag probably the most important aerodynamic factor that we have to consider. And drag is basically a things velocity squared multiplied by it's drag coefficient and it's frontal area. Drag coefficient depends on a lot of factors some of which are an objects overall shape, surface roughness and speed A brick has an awful drag coefficient of one, while a teardrop, the most aerodynamic shape there is, has a drag coefficient of about .05. When you're loafing around at low speed,
1:33 the air's not much to be worried about so there's not much drag and cars have plenty of power to push the air out of the way even if it's shaped like a brick. In the very early days of automobiles, manufacturers really didn't have to car about shape because cruising speeds barely got up to 45, but I don't know, maybe if Model T was more aerodynamic, it could've gone 50. - 50. - The earliest land speed record racers quickly realized streamlining their cars are gonna make it way better for going fast. Because of that velocity squared part of the equation, drag increases significantly the faster you go. Some might call it exponentially. At 70 miles an hour there's four times more drag than there is at 35 miles an hour.
2:18 That means it takes a lot more work to push something through the air. Looking at a fast-moving, non-aerodynamic brick, air's gonna pile up in front of it and create an area of high pressure there. At the back a low pressure air pocket forms and creates a pressure differential. So not only is there frictional drag simply from the motion, now there's another force trying to drag the brick backwards. All this makes drag a really big factor in determining fuel efficiencies and top speeds. A reduction in drag coefficient from point three to point .25 would increase fuel economy by about a mile a gallon. By the same reasoning, an electric car can go further on a charge the more aerodynamic it is. That's why they look so weird. Now that we're regularly cruising at speeds
3:05 over 70 miles an hour, we got a new focus on fuel efficiency or battery range Production car designers try to get the lowest drag coefficients possible. Most modern cars have a drag coefficient somewhere between point .25 and point .35. With SUVs and trucks somewhere around point three and point four. The electric Tesla Model X is a super sleek crossover with one of the lowest drag coefficients of any production car, .24. But if two different cars are going the same speed, there can still be more overall drag on the really aerodynamic bigger car than on a less aerodynamic smaller car You can calculate how draggy a particular thing is by multiplying it's drag coefficient by it's frontal area, which is called drag area
3:51 Let's compare the slippery Model X to the Nissan 350z which has a mediocre CD of .31 with a frontal area of 20.88 square feet, it's got a drag area of six .47. The Model X has a larger frontal area, 27.88 square feet and with it's low .24 drag coefficient, it has a bigger drag area of 6.69, and therefore it's got a bit more drag. More drag. So maybe now you're thinking, 'Hey, F1 cars 'are really fast, I bet they're' crazy aerodynamic Well, you'd be wrong They got a drag coefficient of about point seven, that's more than a minivan, what? F1 cars and most race cars are designed mostly with lift in mind.
4:37 Traction and grip are just as important to fast lap times as speed and power. Turns out keeping a car from flying off of the ground helps improve grip. (revving) (audience cheering) And pressing down on the tires with negative lift; downforce improves grip even more. Down force also creates a ton of drag but the trade-off is worth it because without all that down force, F1 cars would still be spinning their tires at 100 miles an hour and with extra force pressing towards the tires, they get increased lateral grip for better cornering speed A heavy car could achieve the same result but it wouldn't be able to accelerate or corner as well as the light ones So, what's creating that lift or down force? - [Crowd] Yeah.
5:23 - Like our super draggy fast brick with high pressure in front and low pressure in the back it's created by having a difference in air pressure between the top and the bottom of a car. Let's use the 350Z again and say there's a hypothetical one PSI, less pressure on top than underneath, with a surface area of about 12,240 square inches, there'd be about 12,240 pounds of air pressure lifting the car up. That would suck. To get the desired down force, we tapped into a phenomenon called Bernoulli's Principle and that says that a fast moving fluid will have lower pressure than a slower moving fluid. A wing mounted on a car generates down force when air moves more quickly across the bottom of the wing than it does across the top.
6:08 In this case, the fluid's the air. So the slower moving air across the top of the wing exerts more pressure than the faster moving air underneath resulting in Downforce But how do we get the air to do that? Make the wing an air foil shape. When air runs into a curved surface, it'll try to follow that surface and that's called a Coanda Effect - [Men] Words, words, words- - [Woman] Coanda. - [Men] Words, words, words. - And the direction you mount the wing determines whether or not positive or negative lift is generated. The air that has to travel farther speeds up and that creates a pressure imbalance that produces lift or negative lift which is downforce But what if your car's just got a little trunk spoiler tacked on the back?
6:57 Well, it actually does something. Since the air follows a car's curved roof line down a bit and creates a fast and smooth flow, a lower pressure area of lift gets created around the rear end. - [Children] Ew. - The spoiler interferes with the air flow just a bit, helping to cancel out some of the lift. It spoils the air flow It's a spoiler. (laughs) Anyway, they don't generate their own down force, but that's why spoilers give you a little more high speed stability, and if you look at the Audi TT, which is kind of like a jellybean cut in half, it was getting in accidents anything over 110 miles an hour. All they had to do was add a little baby spoiler, problem solved.
7:43 Say you got yourself a big wing, now there's down force pressing on your rear tires. What about the front? A lot of rear down force itself can cause - [Man] Boo, you suck. - And no one wants that. It'd help to balance things out to add down force to the front tires using a splitter Like our brick, air stacks up against the car's front end and creates a high pressure area before moving either over or under the body. When more air goes into that tight space under the car than the amount of air that goes over it, well, you're gonna have lift-off. (revving) (thud) Most production in street cars generate positive lift at high speeds and like the wing, you'd really rather have low pressure air go under the car
8:28 whilst high pressure air goes over the top. When a splitter is added, it the amount of air can stack up against while helping more of it move over the car Now with more pressure on top and lower pressure underneath you've got a net down force on those front tires. We mentioned earlier that there's not much aerodynamic drag at low speed and that means there's hardly any down force either so as much as I wanna believe it, those splitters and shopping cart wings really aren't doing much for the average daily drive. - [Crowd] Aw. - But the good news is that downforce increases exponentially with speed, just like that annoying drag does. - [Man] You suck. - So, what do air dams, canards, under trays, side skirts, vortex generators
9:13 and diffusers do what? No, the people need to know this, Eddie. (light music) Well, it looks like we're out of time. Look, there's so many aero accessories that we can't explain them all in one video. So, guess what? We're gonna do more videos on aerodynamics Spoiler alert! Never miss an episode of Science Garage, we do this every Wednesday. Click this big ol' subscribe button so you don't miss out. You like spoilers? Check out this Up to Speed on the WRX. Check out this Wheelhouse on the best racer according to Nolan. Follow me on Instagram @bidsbarto and follow Donut @donutmedia. Don't tell them how spoilers can be for things over than safety.
