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Brake Fans Vs Ducts


Xph
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So I was watching some circle track stuff the other day, and the driver was switching on fans for rotors...   they used powered brake ducts to better control the temps of individual rotors.

 

Then I came across some places selling inserts to go into the wheel between the spindle and wheel which added fins to make a fan...   this pulls air out from under the car over the brakes..  but in a obviously less controlled way...   I think toyota racing did something similar back in the day with a carbon fiber wheel cover shaped like a fan.

 

Brake+Cooling+0041253744239.jpg

 

f1-2008-spa-xp-0118.jpg

 

Standard-right.jpg

 

that last image, or even slight modifications to the spokes on our wheels would do the same...  and seems chumpy to me, I wonder if it add too much drag...  

 

the bilge blowers are another idea, but of course all of this (other than possibly shaping the existing wheel spokes) would be value add for chump; where the duct work is open.

 

From an aero perspective, I just dont like the holes in the front of the car, nor do I like pushing air under the car...  I suppose with more optimal ducts around the rotor or behind the wheel to prevent air from getting under the car its less of a problem.

 

 

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57 minutes ago, Xph said:

So I was watching some circle track stuff the other day, and the driver was switching on fans for rotors...   they used powered brake ducts to better control the temps of individual rotors.

 

Then I came across some places selling inserts to go into the wheel between the spindle and wheel which added fins to make a fan...   this pulls air out from under the car over the brakes..  but in a obviously less controlled way...   I think toyota racing did something similar back in the day with a carbon fiber wheel cover shaped like a fan.

 

Brake+Cooling+0041253744239.jpg

 

the bilge blowers are another idea, but of course all of this (other than possibly shaping the existing wheel spokes) would be value add for chump; where the duct work is open.

 

From an aero perspective, I just dont like the holes in the front of the car, nor do I like pushing air under the car...  I suppose with more optimal ducts around the rotor or behind the wheel to prevent air from getting under the car its less of a problem.

I toyed with the idea of electric blowers after seeing them used in a NASCAR race.. I think it would be awesome (and as you said... lower drag if you don't need holes in the front air dam). It's one of those projects I would do if I had unlimited time.

Wire the fan with a variable speed (voltage?) switch... you don't want your brakes to be too cool either, and the fan pictured pushes a huge amount of air.

 

Let us know how it turns out :) [I would argue that any form of rotor cooling is 0 points under the 'brake ducts' umbrella rule. It is, after all, to promote effective braking and safety]

Edited by enginerd
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We will probably cut some steel sheet,and twist in some fans like the last pic, and test them at a track day...  my first question would be how would it affect our top speed and acceleration as the fan will cause drag and rolling resistance...

 

After that (depending on how dramatic the effects are in our speed range) we might try reducing fins and or attack angle, or scrap the idea all together...   if its successful however we would then need to monitor rotor temps to select new pads presumably.

 

And yes, if we had more time and budget...  something like a temp monitor and race capture pro to drive the fans would surely be superior.... 

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1 minute ago, thewheelerZ said:

You guys must have too much a) weight on your rear axle and want to even it out with weight on the front wheels and 2) too much reliability causing you to wish for at least SOMETHING to break while you are out on track!

 

its the stuff that happens when the forecast calls for highs in the teens.

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I did the math once and with a 4" hose (dryer vent) like I use, a brake duct in the nose would move more air past 60mph over your standard 4" bilge fan. What NASCAR does isn't always a good gauge of what we should do. They have much denser traffic to deal with (little air on the nose) and primarily use their fans not to keep the brakes from burning down, but to manipulate the temperature and thus pressure change in the tire. It's an on-the-fly chassis adjustment tool. They're also not using your typical bilge fan. In fact, as of the '16 Coke 600 brake fans are now banned. The Gibbs cars were using them to create downforce on the nose.

 

PS - I seriously doubt you'd see any difference on the stopwatch with a chumpcar and brake ducts in the nose vs. none.

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1 hour ago, ross2004 said:

 

PS - I seriously doubt you'd see any difference on the stopwatch with a chumpcar and brake ducts in the nose vs. none.

Agreed, I'm not sure many of us could match lap times consistently enough to draw a definitive answer from testing. If you can, congrats!!!

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the real question is actual gains. creating more circulation via the rotation wheels is generally front upon from an aero perspective. that introduces turbulent flows. F1 teams in the late 2000s and even in 2010, made special covers and wheels to redirect that air down into the ground and to then be sucked in by the diffuser (the key to modern f1 cars, get the most out of the diffuser at all costs possible to get "free downforce out back to maximize L/D). the new fad some f1 teams now employ are hollow hubs that redirect air backwards to try to get the air to reattach to the car sooner after the little sideplates where written out of the rules.  

 

that said the concept for enduro cars where the time delta due to aero from a wheel fan is likely nill compared to longer lasting more reliable brakes. the old school audi, porsche and bmw solutions for turbo fan wheels are likely great here. BBS made some sets for very specific wheels (and even a few non centerlock wheels if you dig long enough).

 

this thread sparked an idea: why not get a 3d printer to print up vanes to attach to a disc that mounted outside the wheel. the vanes will be light and consistent. balancing the wheel could be fun though.

 

honestly, i would say directional vane brake disc would be a better start than the fan wheels. and holes for brake ducts up front are fine. Now what to use for hose: dont go nascar here. use dryer hose only in the last bit where its got to flex a lot. anywhere you can run a smooth bore hose, and the less bends the better.

 

idea: feed the rotor with a fan system connected to  naca ducts on the bottom of a splitter to lower the pressure under that splitter to get a few lb of downforce on the nose. it be a risk (damage, clog from an off,  small chance it gets rubber built up in it) and odds are ground effects would play havoc with it (likely a paper out there on the subject of ground effects and naca ducts though). mender, worth a cfd model?

 

 

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Hmmmm, let me hazard a guess that 75% of the ChimpCars have brake ducting.  Maybe 90% of the ChumpCars do not have a brake issue once they get rotors, pads, fluid, cooling sorted out.  Some cars have cooling ducting stock, my first gen RX-7 had some tin work to direct air to the rotors.  

 

Get everything sorted then fool with the tweaking experiments like some wheel fins.  My $0.02.  

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I swear I've discussed those wheel fans with our engineers in the past and they said they weren't very effective at reducing disc/caliper temps.  It may be just that the racing discs/pads got so much better that evacuating the hot air wasn't as important and, like CHB mentioned, the aero loss was too great for any gains in brake cooling.  I might ask again.

 

The duct fans that the cup teams were/are using in recent years were very custom and capable of some ungodly amount of CFM (way more than that standard attwood).  They also use multiple hoses PER side.  We've found that if you block off the ID of the disc and direct hoses to cool it, you need much more CFM than a single 3-4" hose can provide.  The brakes we tested ran significantly cooler with just backing plates removed and air ducted in behind the front wheels.

 

An easy test to see if brake cooling changes are effective is to get a good temp probe (or good laser if you can afford it), and install your cooling device on one side of the car.  Go do 10 hard laps and have someone take caliper and disc temps on pit road.  While you won't seen the spikes, that should give you a good indication if the devices are helping or hurting in general.

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1 hour ago, Bremsen said:

I swear I've discussed those wheel fans with our engineers in the past and they said they weren't very effective at reducing disc/caliper temps.  It may be just that the racing discs/pads got so much better that evacuating the hot air wasn't as important and, like CHB mentioned, the aero loss was too great for any gains in brake cooling.  I might ask again.

 

The duct fans that the cup teams were/are using in recent years were very custom and capable of some ungodly amount of CFM (way more than that standard attwood).  They also use multiple hoses PER side.  We've found that if you block off the ID of the disc and direct hoses to cool it, you need much more CFM than a single 3-4" hose can provide.  The brakes we tested ran significantly cooler with just backing plates removed and air ducted in behind the front wheels.

 

An easy test to see if brake cooling changes are effective is to get a good temp probe (or good laser if you can afford it), and install your cooling device on one side of the car.  Go do 10 hard laps and have someone take caliper and disc temps on pit road.  While you won't seen the spikes, that should give you a good indication if the devices are helping or hurting in general.

 

 

the wheel fans do help a bit. they should help increase mass flow thru the brakes. reasons to use: cannot increase are prior to the rotor, so increase the velocity thru it. suck the air thru the system. 

 

the reason the 80s and road inspired race cars used them: they needed more help getting air thru the brakes. they could not get enough air into the brake components, so use the rotating wheel as a pump to pull more thru. wheel/tire sizes effected the brake sizes back then (actually a big issue with f1 too, but). material selection for brake components didn't help (a situation that chumps face, that f1 does not). honestly the same reasons are there to go for the turbo fan wheels, but alone they are not helpful. as you said, the priority for nascar, and production based cars is getting as much infeed air to the brakes as you can to start. unless you can make a really effective pump out of the wheel fans (which is a variable rpm pump), they just are not as easy as adding more area and hence mass flow prior to the brakes. plus the aero effects suck (you mess up the flow with them).

 

all chumps should be using ducting to the inside of the rotor, and if possible the get the best vented rotors possible. more vanes, and directional if possible. that will pull air in from behind the rotor hat.

 

with that in mind: DIRECT AIR INTO THE ROTOR! there is more surface area inside the rotor than on 1 side of the rotor. so get a shroud to force the air inside the rotor and don't just dump air on the surface! next MOAR AIR. get as much as you can to the rotor center and tech will allow without points. bigger hoses, multiple hoes, anything. at worst you can close the openings if the brakes cant get up to temp to recoup aero efficiency. next route the air efficiently from the inlet(s) to the shroud. so that corrugated ducting you are using, yeah get rid of as much as you can. from a flow point of view it, that irregular wall is the devil's son (rotating cylinders are the devil, irregular cylindrical tubes are #2 on the aero no-nos). get less flexible smooth bore tube and run it close to the spindle/shrould, then couple it to a short corrugated flex. after this explore more interesting ways to increase the flow prior to the brakes (https://www.linkedin.com/pulse/air-ducts-down-earth-guide-motorsport-applications-willem-toet). some interesting applications there. once all this has been exhausted, turn to the wheel fans.

 

off topic but:

 

modern F1 teams used the fans in the wheels, but they catch has always been redirecting that air. once they figured that out, they went nuts with the fans in the wheels. interesting read on what they were doing with the air going thru the wheel with the little fairings outside the wheels around 2009 and 2010.

https://www.aps.org/units/dfd/pressroom/papers/axerio.cfm

 

the honest answer from an aero guy: cover the dang thing up! its a drag monster and mucks up the flow. the fairings outside the rims on the f1 cars actually did that with 3 side benefits:

 

1: ability to use a fan system to pull more heat out than before with little difference in drag (actually lower than before)

2: the ability to direct all that going thru the brakes air and back to the diffuser.

3. clean up inboard air around wheel (the real odd side benefit). this helps air get under the diffuser and stay less turbulent and more effective under the car.

 

 

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I run forced brake cooling (bilge type fans, but big ones made for that purpose). It radically improved my pad life, to a point where the brake consumption was managable. No change in feel or stopping power, except we didnt go metal to metal. 

 

Crossover speed for these fans vs open cooling is well above 60 mph. I doubt most people's brake hose routing results in measurable positive pressure at 80 mph. Keep in mind average speeds for most races we do are 60 to 80 mph or less. I destroyed cooling on lf of car one race and went metal to metal on that brake, with about half pad left on the other side. 

 

At work we do use very high powered fans, but crossover speeds for brake cooling is in the triple didgets. They are not just for aero.

 

No attempt was made on the chumpcar to do this for aero gains. I think the difference in laptime from that aero would not be measurable. Losing the brakes from full pad consumption is measurable. 

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http://publications.lib.chalmers.se/records/fulltext/176302/176302.pdf  good read on the subject...
 

Compares the drag of a fan based rim against a fully covered rim see section 5.2.1

 

Quote

One configuration that deserves special attention is the Fully covered rim since it was already known for producing really good results for aerodynamic drag force [37]. Its performance in terms of ventilation resistance was slightly below average. This may have several explanations. Firstly, having no openings in the rim permits an attached flow on the outer side of the rim; this can result in increased surface friction. Secondly, with such a configuration the air cannot pass through the rim and the pressure inside the wheelhouse may be affected.

Quote

 

As expected, changing the wheel rims did not have as significant effect on the aerodynamic drag of the vehicle as it had on ventilation resistance of the wheels themselves. Also, as predicted, the Fully covered rim design produced the lowest aerodynamic resistance

 

 

per this research going from a fully covered wheel to a fan type resulted in about a 3.5% increase in overall CD...  and that the fan out beat the base spoke configuration of a 5 spoke wheel by about .5%

 

Maybe we will see fins attached to wheels in 2017;

Edited by Xph
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52 minutes ago, tommytipover said:

So at ~60 MPH a good fan might move more air than a hose and duct?

Black Magic [Drew] is saying the fan's he uses move enough air [cfm] to simulate more than 60 mph worth of cfm. So until you get to say 65 mph, the fans are moving more air than just hose and duct and ambient, non forced air. Beyond that, hose and duct move more cfm. He works for a little known race shop, JGR [that's Joe Gibb's Racing for guys not in the know like @red0 :)] so he might know a thing or two based on empirical data, I would presume.

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  • Technical Advisory Committee
31 minutes ago, dimitri.mariutto said:

Black Magic [Drew] is saying the fan's he uses move enough air [cfm] to simulate more than 60 mph worth of cfm. So until you get to say 65 mph, the fans are moving more air than just hose and duct and ambient, non forced air. Beyond that, hose and duct move more cfm. He works for a little known race shop, JGR [that's Joe Gibb's Racing for guys not in the know like @red0 :)] so he might know a thing or two based on empirical data, I would presume.

 

I would have never got JGR, but I have heard of Joe Gibbs Racing. I am guessing it is a nascar shop?

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I will note that our local track we run is Road America, and at this track we typically dont have trouble cooling brakes, like we do at shorter tracks like Blackhawk Farms..   the average speed for chump-cars is around 81mph for cars at a 3 minute pace... maybe up to 89mph average for the faster ones.

 

I wonder if we used a couple of heater core fans under the front behind the splitter to feed the rotors... they are a bit heavy but  hmm

Edited by Xph
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2 hours ago, Black Magic said:

I run forced brake cooling (bilge type fans, but big ones made for that purpose). It radically improved my pad life, to a point where the brake consumption was managable. No change in feel or stopping power, except we didnt go metal to metal. 

 

Crossover speed for these fans vs open cooling is well above 60 mph. I doubt most people's brake hose routing results in measurable positive pressure at 80 mph. Keep in mind average speeds for most races we do are 60 to 80 mph or less. I destroyed cooling on lf of car one race and went metal to metal on that brake, with about half pad left on the other side. 

 

At work we do use very high powered fans, but crossover speeds for brake cooling is in the triple didgets. They are not just for aero.

 

No attempt was made on the chumpcar to do this for aero gains. I think the difference in laptime from that aero would not be measurable. Losing the brakes from full pad consumption is measurable. 

 

how many points for the fans? thats been my resistance to them. free, 5 each, at cost (hope not)? for effectiveness sure, mass flow goes up which means you can take more heat away from the rotor. whats the amp draw, negligible? 

 

its an electrical way to do the wheel fan covers, at likely a more effective means if free or really low point value..

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Hmm dreaming...  while again probably not worth the value add..  something like this

 

Spal 008-B45-02 & 008-B46-02 Replacement, Tonada DC Blower

 

These are 1.8kg ish, 700cfm draw 15amps 12v...  for 70$ ish...  but here is a 25$ version that draws 22amps...

 

http://www.tonada.com.sg/index.php?route=product/product&path=35&product_id=216

 

Something to consider, the direction of travel for the fan is not ideal for this use though...

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#1

simple design, likely could be done in the garage in a afternoon with a welder and the original dust shields

c6z06comp.jpg

main.php?g2_view=core.DownloadItem&g2_itemId=21722&g2_serialNumber=1

 

vs:

 

#2

nascar and formed carbon fiber 

9f9cb082f43446d8112197f939061690.jpg

 

 

vs

 

#3

Singular_3inch_miata_brake_ducts.jpg

nascar solution is great, but fab work for that vs #1?

i'll admit #2 would get everything you want, center, caliper, hit the hot surcafe too before going thru the rotor, but is it a solution chumps can obtain (well ebay, but be a bidding war). wonder if i got them out of aluminum off ebay how much many points they would be worth vs #1.........

 

#3 might just be all you can do if you have tiny rotor hats and cant get access to the center of the rotor like #1 on the vette. they do seal up to the center of the disc to force the air across the rotor and then inside the rotor .

 

i personally like the idea:

header-image2.jpg  

 

but instead of a 3d printed part, maybe aluminum dryer tubes and bends. the corrugated part is only needed where you know you must have some flex for stearing suspension movement.

 

oh and bilge pumps, blackmagic which ones do you use?

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I used water cooled brakes in my IMSA & Trans Am cars.  

 

 I doubt Chump Cars really need a lot of air.  I would start by using temp paint or strips on the rotors and calipers and check your brake temps first.  

Edited by DEE DEE
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I use 4 of these. One for each brake hose. 17 bucks each.

 

http://www.sriperformance.com/mobile/Product.aspx?ProductCode=DET-754-BLOWER

 

Remember this is inline to a good duct and hose to caliper and rotor. You really want pad and rotor cooling. Since it is an inline fan the "crossover speed" is the speed where the fan actually inposes a resistance to the normal flow. As the pressure builds in the duct from speed the fan will speed up, so the static output isnt the max output. 

 

I actually us some old nascar caliper ducts that i cut up to fit the neon. From the used parts places here i bought the fans, ducts and caliper ducts with hoses and a wiring harness for less than 200. 

 

Keep in mind the system will draw up to 20 amps continous on a hot day...need a decent sized wire.....

 

Bigger inline fans exist if you want them....i have a few 7 amp units for tge next car, but 30 ish amps for 4 is alot....

Edited by Black Magic
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Our biggest problem is to allow the wheel to turn.. There is just not enough room for the single three inch duct we have

 

we made a dust shield with a tube but there was just too much range of motion...  So we ended up just terminating the tube a few inches from the caliper attached to the lower control arm so it didn't have to turn...

 

maybe if we used inch and a half or two inch we could run more lines but from a practicality and simplicity standpoint the wheel fan is very intriguing..

 

we also were considering using a "dust shield" that filed the entire back of the wheel vs one that covered the brake rotor...  Helping get the air to do the right thing without having to get a 3" tube into the tiny space between the caliper and hub..

 

our next gen was going to be rigid ducts better shaped with expanding area..  Trying to increase the air velocity but still terminating on the control arm a few inches from the actual caliper / hub location...

 

with the tire package we have there just isn't enough room between the tire and frame for the nsacar type of duct.. 

Edited by Xph
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