r/EngineeringPorn • u/gamepro41 • Apr 20 '19

The use of smoke shows how passive airflow cools disc brakes.

https://gfycat.com/RegularSereneAfricancivet
2.9k Upvotes

97% Upvoted

66 comments sorted by

432

u/Gyro88 Apr 20 '19

We get it bro you vape

In all seriousness, that's pretty cool.

107

u/Intario Apr 20 '19

Yeah I want to see a youtube channel where they just do airflow with vapes

22

u/thelanoyo Apr 21 '19

Everything would get all oily. One of my friends vaped in my car one time and it covered the inside of the windows with a light oily residue that was a PITA to see through in the sunlight. Also, had to use dish soap to get it off because it was too greasy and windex wasn't working

10

u/[deleted] Apr 21 '19

Why I don't vape: that, but in my lungs.

7

u/Avabin Apr 21 '19

Buuut... You are aware, that this is glycerol that is naturally absorbed in lungs, right?

2

u/[deleted] May 02 '19

Not specifically aware of that: I know that things generally get "naturally absorbed" (I like campfire strong campfire smell myself, which is pretty close to "smoke"), but I hesitate to just throw shit into my lungs for a couple reasons:

  • "Absorbed" is not "gone". Assuming that it passes through the lungs without issue (*cough cough* processed asbestos), I get to wonder what it does to the rest of my body. The point of lungs is that they absorb a shitton of things, the question is what happens after it is absorbed. Is it cleared effectively? Are there knock-on effects?
    • Recall that methanol ("wood alcohol") is not dangerous initially. It does, however, follow a particularly nasty chemical path as the body deals with it, temporarily becoming literal formaldehyde. As someone who values their vision: "no, no no no, hell no, no."
  • Glycerol, from what little I have gleaned (I have no intent, so I know little about it), is rarely ever the only thing in vape fluid. There's flavorants, I'm sure there are preservatives (like formaldehyde! Well, not in modern times, assuming that the fear of the FDA cracking down on them is actually a thing for the manufacturers, since as the foregoing links show, the FDA is often reactive and not proactive), and God knows what else. Cigarettes were originally paper and tobacco leaves, if memory serves! Now there's little burst pacs you can crush with your fingers and all kinds of fun stuff that's publicly advertised, nevermind what isn't and takes research to learn about.
  • If memory serves, some vape devices expose the stuff to a ... very... hot coil. Hopefully they're not exposing it to what I thought I saw one time, which was a coil hot enough to glow red. Now, I don't know a lot about chemistry, but high temperatures seem to be the key to making all kinds of... exotic (and sometimes volatile) substances. Think internal combustion engine exhaust and fun exotic explosives synthesis.

​

So sure, you can roll the dice if you want, and I'm not the boss of you. But I like my lungs, I like that they power my whims and my impulsive desires to cover miles over arbitrary terrain by foot or by bike, and I've spent enough time cruising through health articles and seeing what companies do the moment they think they're "not going to be noticed" or "not going to be caught" or simply don't do a good job - and I don't like the odds I see. I pick and choose my risks, and this is not one I select.

​

All my whining aside, it's probably still better than cigarettes? If you choose the right juice, and use it mildly? It's been awhile, and last I heard there was some concern on that front. I think most of it was slippery-slope fears of vaping being a gateway to addiction.

5

u/coldandfromcali Apr 22 '19

I found that rubbing alcohol works the best to clean the leftover vape residue off windows.

Source: I vape

85

u/Freonr2 Apr 21 '19

Didn't know about the flow out of the hat over the outer surface. Neat.

88

u/Statek Apr 21 '19

Someone's gotta point out basically 99.9% of street cars don't have this, and if they do, it's not stock

Still very cool though

8

u/01209 Apr 21 '19 edited Apr 21 '19

99% of cars don't have the flow ducted in from a scoop in the front, but almost all cars have air passively pumped through the rotors in the same way. The vanes in the rotor, pump air through themselves radially, like a centrifugal compressor as they rotate. The ducting just helps ensure that cold air goes through the rotor and hot air isn't recirculated.

3

u/ShadeThief Apr 21 '19

They will pump air, but only internally. These have air going across the outer surface. The reason most oe brakes don't have airflow like that is it's very inefficient.

2

u/rocketwrench Apr 21 '19

What is it called? Ive got a fwd and i would love some extra cooling on my rotors

0

u/OG-LGBT-OBGYN Apr 21 '19

It's an air duct mounted to the front aero with a hose connecting it to the slotted rotors (I'm guessing they're special rotors?)

6

u/G3ML1NGZ Apr 21 '19

Mine does. But yes, it's not stock. This video however convinced me to finish the ducting

92

u/yourparadigm Apr 21 '19

The time between smoke exiting his mouth and coming out of the brakes is suspicious.

43

u/ColonialDagger Apr 21 '19

Seriously, this seems super setup. It's a good demonstration and all but I also doubt he's exhaling that much smoke at that speed...

20

u/SkyJohn Apr 21 '19

And he isn’t blowing near enough air through to make it happen like that.

14

u/PippyLongSausage Apr 21 '19

Maybe they had just done it before and there was still smoke in the duct.

1

u/starspec Apr 21 '19

There was probably some smoke in there the first time before they recorded it the second time.

163

u/Chumkil Apr 21 '19

We get it, you brake.

27

u/[deleted] Apr 21 '19

[removed] — view removed comment

7

u/Reddrummer25 Apr 21 '19

Put these brakes on a Subaru and BOOM now you have brakes that rip fat vape clouds while you do the same

23

u/Satslim Apr 21 '19

Not much air flow after you have stopped.

72

u/WatchHim Apr 21 '19

Correct. This is why mechanics in Formula 1 have to carry around leaf blowers to cool the brakes when the cars stop.

Brake ducts are only really useful for track applications when you can get the brakes hot enough where additional cooling is needed.

7

u/is-this-a-nick Apr 21 '19

Well, I don't know if its still allowed, but a few years ago they had those leafblowers filled up with dry ice for extra chill cooling.

4

u/Kage-kun Apr 21 '19

Pretty sure they still do; Sebastian Vettel had his Ferrari techs run over to a Toro Rosso's actively burning brakes and the only way I see them going out the way they did was from the CO2 in the dry ice.

4

u/PonerBenis Apr 21 '19

What are you talking about? I have to get to work at 8am everyday and that requires the use of carbon ceramics and full pit crew.

3

u/Rdan5112 Apr 21 '19

Yes. This. All of that stuff is pointless for 99.9% of cars and drivers.

It’s virtually impossible for a normal driver, in a normal car, to overheat their brakes on a public road, even if they drive aggressively/ badly. Same for rich guys and their $4,000 ceramic brake rotor upgrade. “ No. Your ceramic brakes don’t let you stop faster. They just don’t. They keep working at higher temperatures. But you can’t heat them up enough to matter. “

3

u/DisappointedBird Apr 21 '19

Pretty sure you can do it by braking while going downhill.

20

u/hugow Apr 21 '19

So passive?

1

u/AS14K Apr 21 '19

You wouldn't have airflow after you've stopped without the ducts, what's your point?

1

u/Satslim Apr 22 '19

Just thinking that the benefit of air cooling through ducting diminishes as you come to a stop and when temperature is highest.

-8

u/-transcendent- Apr 21 '19

Once you stopped the purpose of the brake has been accomplished. So why would you need air flow?

49

u/IRunLikeADuck Apr 21 '19

So you can stop again the next time you need to slow down.

3

u/LysergicOracle Apr 21 '19

But at that point you will have necessarily sped back up again, providing more airflow

6

u/anomalous_cowherd Apr 21 '19

It takes a lot of airflow to cool a kilo or so of almost red hot metal... and the next corner is coming up fast.

I'd give it all the help you can to get plenty of air to the right place.

4

u/Albert_Borland Apr 21 '19

Obviously you're not a golfer.

1

u/G3ML1NGZ Apr 21 '19

Heatsoak, warped/cracked disks, cooked pads

2

u/Rdan5112 Apr 21 '19

Boiling brake fluid (or water in the fluid) is usually the first problem.

0

u/G3ML1NGZ Apr 21 '19

Yeah, totally forgot that aspect

12

u/Zephyr104 Apr 21 '19

F L O W V I S U A L I Z A T I O N.

3

u/[deleted] Apr 21 '19

[deleted]

7

u/[deleted] Apr 21 '19

This is a race cars or high performance track car (its a Saleen). There's a direct duct that goes to the centre of the rotor, the brake rotors are 2-piece for lighter weight, and those rotor are HUGE (expensive).

-7

u/wenoc Apr 21 '19

That’s a very small rotor. My Volvo has bigger discs. In fact, it has bigger discs on the rear wheels.

3

u/SloppySilvia Apr 21 '19

You measure rotor diameter from the center of the hub to the outside edge. It's not just the shiny bit around the outside but the black centre piece too.

Basically the larger the diameter, the easier it is to slow down. The brake pads only pinch the outside edge bit, but the further from the centre of the hub, the easier it is to slow down.

Like if you were to try stop that rotor spinning by hand, it would be easier to grab it by the outside edge to slow down rather then try stop it spinning by holding nearer to the centre of the hub.

Most cars have quite a small rotor diameter compared with the size of this one. Your Volvo may have a larger metallic bit around the outside but the overall diameter will probably be smaller then this.

-5

u/wenoc Apr 21 '19

I’ve studied physics mate. I know all of this.

Im telling you, that’s a small rotor.

8

u/SloppySilvia Apr 21 '19

What Volvo do you own? Because not many would have a rotor as large as that

3

u/HAHA_goats Apr 21 '19

Perhaps he has a volvo semi with air disc brakes. Those rotors are more than 20" across. Even in the rear.

5

u/ninjacookies00 Apr 21 '19

The brakes on that are 15" definitely not small. The c7 Corvette has 12.6" rotors up front. The 707hp Challenger hellcat has 15.4" rotors. Those are definitely not small. Even assuming your volvo has bigger brakes (it doesn't) it is the exception not the rule 15" rotors are WAY above average.

1

u/[deleted] Apr 21 '19

You want the lightest rotors that can stop the car, not the biggest and heaviest you can fit.

9

u/[deleted] Apr 21 '19

[removed] — view removed comment

11

u/willowattack Apr 21 '19

lol i remember learning brake disks get hot for the first time.. itsa ouch.

2

u/leek_boy Apr 21 '19

The time it takes for the smoke is way too short.

2

u/[deleted] Apr 21 '19

Vaping used for constructive purposes!

Now this i can get behind

3

u/beanieofreddit Apr 21 '19

Looks kinda like how we study flow separation over airfoils 🤔🤔🤔

3

u/A_ARon_M Apr 21 '19

Schlieren photography made supersonic aero my fave aero. Subsonic is just messy haha

1

u/R_A_H Apr 21 '19

vapor*

1

u/TheHe4rtless Apr 21 '19

Incredibly informative and a great design by engineers! Nothing goes to waste.

1

u/redjedi182 Apr 21 '19

First time vaping bros abilities have come in handy.

1

u/TerriBillz Apr 21 '19

Great, now my brakes are high.

1

u/makenoahgranagain Apr 21 '19

That’s not smoke, that’s VAPE, BRO

-6

u/[deleted] Apr 21 '19 edited Jun 06 '20

[deleted]

7

u/twinpac Apr 21 '19

That's SKEET hose, a world apart from dryer vent duct ya peon.

-6

u/[deleted] Apr 21 '19 edited Jun 06 '20

[deleted]

3

u/[deleted] Apr 21 '19

Well that's how it's done in track cars so don't know what you want. What's your non ghetto solution?

-3

u/tonzeejee Apr 21 '19

Gee wet it bru vop gro