brake ducts - compliant or not with the GCR

[Art Smith]

since the club is no longer providing a means for competitors and suppliers to get a binding Court of Appeals compliance opinion on matters of interest, those with questions are left to go it alone or seek qualified opinion(s) from the community accepting the associated risk with that approach. to that end I'm seeking qualified opinion(s) traceable to the GCR on the very specific and limited question:

are brake ducts compliant with the GCR as currently written?

note: it's not being asked if brake ducts have been used for the last 50 years OR if brake ducts are required with the hardware used by most competitors on most days at most tracks in the US OR if they're a good thing or bad thing OR ugly OR pretty Or anything else. very simply: are brake ducts compliant with the GCR as currently written?

I believe brake ducts are compliant with the GCR as currently written for these reasons:

per section 8 of the GCR, brakes are unrestricted with two noted restrictions AND the global restrictions on materials from section 2.

8. Brakes
Unrestricted, except:
a. Maximum of 2 pistons allowed per caliper. Calipers must be ferrous or aluminum alloy.
b. Brake rotors are restricted to ferrous material.

2. General Construction Restrictions
NOTE: Contained herein are the 1986 Formula F chassis construction requirements, revised January 1, 2013. All new Formula Continental and Formula F cars are to be built to these specifications. Any class-specific differences are stated explicitly. For cars registered prior to January 1, 1986, see section B.21. The use of carbon fiber and/or Kevlar reinforcement, titanium, beryllium, metal matrix composites, ceramics, high
strength composites and similar materials is prohibited unless specifically permitted. The use of the word “unrestricted” in any section does not indicate the allowance of these prohibited materials. The use of non-metal materials for seals, bearing and bearing liners, thread locking systems, windscreens, mirrors, instruments, wiring, electronic systems, electrical systems, hydraulic and oil and cooling systems, etc, are permitted unless specifically restricted.
Fuel Capacity: Maximum capacity 41 liters (10.83 gallons)
Refer to the Formula F and Formula Continental Dimensions Table for
general dimensional limitations.

since brakes by definition are NOT chassis, bodywork, aerodynamic aids, suspension, steering, wheels, or engines, none of the restrictions from those paragraphs are applicable. "brakes" are not defined in Appendix F. Technical Glossary

Appendix F. Technical Glossary

Brake Light – A signaling light mounted on the rear of the car, which may
be actuated only by driver braking actions.
Brake Lining/Pad – Replaceable friction material which accomplishes
braking action by making rubbing contact with the brake drum or rotor.
Brake Rotor – The disc component of a braking system, which is attached
to a wheel hub and provides a friction surface for braking actions.
Brake Rotor Hat – The integral part of a brake rotor or a separate component
that locates and provides attachment for the brake rotor to the hub.
Braking System – A system, including hydraulic and mechanical components,
which allows the driver to reduce the velocity of a car.

duct(s) to acquire, meter, manage, and exhaust air for cooling brakes easily falls under the umbrella of mechanical components even if the more restrictive definition of "braking system" were to be used in lieu of the much broader undefined term "brakes".

Art
artesmith@earthlink.net

[David Ferguson]

I don't know if I'm qualified, and I didn't sleep at a Holiday Inn last night, but I will agree with your argument that they are legal as brakes are unrestricted save caliper and rotor material.

[HayesCages]

"c. Formula F and Formula Continental are restricted classes. Therefore, any allowable modifications, changes, or additions are as stated herein. There are no exceptions. IF IN DOUBT, DON’T"

I suppose if they could be considered a part of the upright, which is 'free', but then would have to made of a metallic material since composites are not allowed for uprights.

Just the same, if you have to bolt something to any other would it be considered a single part?

[DanW]

I question the need for brake ducts at all.

Besides, brakes just slow you down.

[steve zemke]

When I researched this a few years ago, I came to the conclusion that brake ducts were legal. I was thinking about cleaning up the airflow around the inner part of the wheels.

[HayesCages]

We boiled the fluid in the rear (LD19) calipers on our FC at Portland the last time we were there...

[DanW]

We boiled the fluid in the rear (LD19) calipers on our FC at Portland the last time we were there...

And that would be a reason, for an FC. Anyone with an FF who boiled their brake fluid or destroyed rotors & pads?

[HayesCages]

I will add we'll be inserting stainless steel shim stock between the pad and caliper pistons prior to next season to solve the boiling problem.

Art: Are you wanting to run a more aero wheel and duct the cooling air to the brake assy. rather than using wheels that pump air through them?

[JerryH]

By the definaton of "bodywork" in the gcr, brake ducts could be bodywork. Then the max bodywork width rules, forward facing duct rules, and material limitations would all come into play.

Jerry Hodges

[Purple Frog]

Just reviewed the most recent GCR...

There are provisions for legal openings in the bodywork for brake cooling. Obviously, a rule rooted in history when some cars had inboard brakes. Legal bodywork isn't more than 90 cm wide. Ducts hanging on the uprights would not be bodywork.

I also believe there is provision if you built them, they could be of carbon-fiber because of the exclusion rule that covers many minor items such as mirrors.

I have seen them employed without ever being ruled illegal or even protested.

The most recent nicely designed front brake duct units were employed by Remy Audette in 2010. He soon removed them.

Why? Mainly because they aren't needed, secondly, why add drag to the car when they aren't needed?. (I'm addressing FF, FC and FB.... not S2/P2)

In the past few years the leading brake manufacturers have improved the alloys in the rotors and the makeup of the pads leaps and bounds beyond those of just 5 years ago. Performance Friction's new products are one example.

Much of the drop in lap times in the past few years is due to the improvement in braking. Braking distances have shrunk a bunch.

In some cases now, on cold/cool days the issue is more of one to get heat into the brakes at the end of a long straight. Think Mosport, Road Atlanta, Daytona.

Case in point, the pros are using common Dot 4 fluid with no heat issues.

The pro teams with heat sensing tape/paint on their rotors and calipers are seeing no heat issues.

As a national scrutineer, if faced with having to make a judgment, I would have to rule on a case-by-case basis. If it appeared to be simply a brake duct... OK. If it looked like an excuse to alter the air flow behind the rear of the tire... I'd tell you to remove it.

IMHO, ducts are not needed if you employ the newest calipers, rotors, and pads.

As always, YMMV.

[SEComposites]

Ah, but you are assuming this thread is about brake cooling

[Brian]

My first thought was that brake ducts are obviously not part of the braking system. They play no part in actually braking the car. They do manipulate air flow, so maybe they are aerodynamic. If anything they become part of the suspension or upright, so those rules might apply ( ie metallic, etc). What they do is cool, so the closest thing they come to is part of the cooling system, unless cooling system is further defined as engine cooling or transmission cooling, which I don't think it is. But I really don't think they are part of the braking system. In the same vein, the engine cooling system is not defined as part of the engine rules. Why would anyone think that brake cooling was part of the brake rules?

Brian

[HayesCages]

Maybe FF and FC could adopt this into the GCR:

11.4 Air ducts:
Air ducts around the front and rear brakes will be considered part of the braking system and shall not protrude beyond:
- a plane parallel to the ground situated at a distance of 160mm above the horizontal centre line of the wheel;
- a plane parallel to the ground situated at a distance of 160mm below the horizontal centre line of the wheel;
- a vertical plane parallel to the inner face of the wheel rim and displaced from it by 120mm toward the car centre line.
Furthermore:
- when viewed from the side the ducts must not protrude forwards beyond a radius of 330mm from the centre of the wheel or backwards beyond a radius of 180mm from the centre of the wheel ;
- the ducts may not rotate with the wheels nor may they, or any of their mountings, protrude axially beyond the outer face of the wheel fastener;
- no part of the car, other than those specifically defined in Articles 12.8.1 and 12.8.2, may obscure any part of the wheel when viewed from the outside of the car towards the car centre line along the axis of the wheel.
All measurements will be made with the wheel held in a vertical position.

[Dave Harmison]

I don't have a dog in this fight as I race a Club Ford, but if I was going to Daytona next fall I would certainly have brake ducts and Kephart style wheels.

I could run CFD on a wheel and prove that the valve cap modifies the airflow behind the wheel, it's just a matter of magnitude, so that is a spurious criteria in my opinion.

As to whether brake ducts are required or not, that is certainly up to the competitor's judgement. I would say, of course they are required, either to increase or decrease airflow. In a perfectly tuned car the airflow would be in the Goldilocks zone, not too much, not too little, but just right. How would you get it just right without ducts?

I like Mr. Hayes' approach. Write a rule that makes a space to play in, then play the game. Better than trying to interpret an intent. Clear, specific, enforceable rules are good in my opinion.

[Speed Sport Engineering]

Speaking from personal experience, I would caution putting too much effort into making "brake ducts". Maybe the FF community is more open to cleverness then the FV world, but I would caution anything like that, if percieved as an advantage, might be short lived. Plan your timing carefully.

http://www.apexspeed.com/forums/showthread.php?t=54480

[racerdad2]

And.... will they add downforce ?

[steve zemke]

It all depends on how well you design them.

[HayesCages]

1. lower drag
2. increase down force
3. reduce un-sprung weight.

[HayesCages]

oops...

[Modo]

you don't need brake ducts, special brake fluid, or special brake pads (lightweight car) except pads need to fit caliper ...............

[HayesCages]

Card?
Hit me...
21!

[Brian]

A good brake duct will reduce overall car drag, increase downforce directly on the tire where you want it the most, and let you run significantly smaller and lighter calipers and pads, for reduced unsprung weight overall and reduced parasitic drag from the pads on the rotors. That's if you design your overall system to require brake cooling ducts in the first place. How about designing the upright to run smaller and lower friction bearings that require cooling to survive? I've seen air cooled bearings in "big car" uprights.

The question still is what rules do they fall under. I still don't think they are part of the braking system.

Brian

[Raceworks]

If people put all the energy & effort they do trying to find ways to creatively reinterpret the rules and channeled it into physical fitness and practicing racecraft, racing would be both more competitive and a lot cheaper.

[DaveW]

My opinion only, few real facts...

I had brake shield/ducts on my F2000 for a short time. I could detect no difference in straight-line speed. However, the effect on brake cooling was interesting. I initially had very small ducts - these restricted airflow to the front calipers too much, and I boiled the fluid. I then put on somewhat bigger ducts - these over-cooled the rotors/pads, resulting in unpredictable braking bias front to rear as the pads rapidly warmed and cooled over the course of a lap.

On top of that, they were always in the way of changing pads, measuring camber (I measure on the brake discs - less runout than the wheels or tires), etc., so I quickly gave up on the idea.

[Steve Bamford]

If people put all the energy & effort they do trying to find ways to creatively reinterpret the rules and channeled it into physical fitness and practicing racecraft, racing would be both more competitive and a lot cheaper.

Shhhh! Don't give any good ideas.

[Chris Livengood]

We put spats on our one RFR not for streamlining but rather to increase brake temps.

[Art Smith]

this has been a very interesting experiment; Thanks for the 25 posts to date. I'm amazed at the range of answers to a simple compliance question: lots of curiosity, opinions they're not needed, related experience from another class, current events, a proposal for a new rule, a reference to classical literature, and an opinion on compliance of brake ducts with stated traceability to the GCR. I don't know if my question is answered, but clearly have learned a great deal.

to the wide spread curiosity, in aerospace it was always considered good form to understand the compliance issues in the neighborhood before starting to juggle things looking for more performance. so yes, the compliance question relates to potentially looking for more performance and not less. the real Pro's that know their way around Daytona arrive in February with the smallest brakes and smallest brake ducts they will use all year and yes they don't bother with the infield. while I haven't spoken with any of the team engineers, the physics support three obvious potential motives: reduced polar moment of interia for improved acceleration; reduced unsprung weight for improved grip; and finally a lower overall center of gravity for better overall handling. given the importance of the race in February and the importance of the race that will be held in the fall next year, I'm wondering if there's a track specific braking package that might offer safe performance advantage(s) (NOT equal braking performance) for the fall race.

since the kinetic energy of our cars is not currently being recovered for reuse, that means the energy has to be dumped in the form of heat from the brakes. another forced convection heat transfer problem just like dumping heat from the engine! I concluded that duct(s) to acquire, meter, manage, and exhaust air for cooling the brakes was the obvious lynch pin to all potential combinations that might yield one or more track specific performance advantages and therefore elected to solicit the community's help on compliance (old habit). thinner rotors, smaller diameter rotors, lighter calipers, Penske style wheels, dumping heated air outboard or inboard, ............. makes for a number of interesting combinations to think about. since the NACA technical report on Submerged Ducts was released in the late 1940's, brake ducts don't necessarily imply more frontal area to me so there's definitely the potential for winning on multiple fronts. I was thinking a little further along the path Brian described; a stream and two small hills further out there's an old guy named Rod Sterling that still greets passerbys at the gate with an engaging smile.................

Art
artesmith@earthlink.net

[DanW]

Art, your post confirms my thoughts that something is brewing at the SkunkWorks.

Regards,
Dan

this has been a very interesting experiment; Thanks for the 25 posts to date. I'm amazed at the range of answers to a simple compliance question: lots of curiosity, opinions they're not needed, related experience from another class, current events, a proposal for a new rule, a reference to classical literature, and an opinion on compliance of brake ducts with stated traceability to the GCR. I don't know if my question is answered, but clearly have learned a great deal.

to the wide spread curiosity, in aerospace it was always considered good form to understand the compliance issues in the neighborhood before starting to juggle things looking for more performance. so yes, the compliance question relates to potentially looking for more performance and not less. the real Pro's that know their way around Daytona arrive in February with the smallest brakes and smallest brake ducts they will use all year and yes they don't bother with the infield. while I haven't spoken with any of the team engineers, the physics support three obvious potential motives: reduced polar moment of interia for improved acceleration; reduced unsprung weight for improved grip; and finally a lower overall center of gravity for better overall handling. given the importance of the race in February and the importance of the race that will be held in the fall next year, I'm wondering if there's a track specific braking package that might offer safe performance advantage(s) (NOT equal braking performance) for the fall race.

since the kinetic energy of our cars is not currently being recovered for reuse, that means the energy has to be dumped in the form of heat from the brakes. another forced convection heat transfer problem just like dumping heat from the engine! I concluded that duct(s) to acquire, meter, manage, and exhaust air for cooling the brakes was the obvious lynch pin to all potential combinations that might yield one or more track specific performance advantages and therefore elected to solicit the community's help on compliance (old habit). thinner rotors, smaller diameter rotors, lighter calipers, Penske style wheels, dumping heated air outboard or inboard, ............. makes for a number of interesting combinations to think about. since the NACA technical report on Submerged Ducts was released in the late 1940's, brake ducts don't necessarily imply more frontal area to me so there's definitely the potential for winning on multiple fronts. I was thinking a little further along the path Brian described; a stream and two small hills further out there's an old guy named Rod Sterling that still greets passerbys at the gate with an engaging smile.................

Art
artesmith@earthlink.net

[Brian]

If people put all the energy & effort they do trying to find ways to creatively reinterpret the rules and channeled it into physical fitness and practicing racecraft, racing would be both more competitive and a lot cheaper.

I wonder why people leap to the conclusion that the guy who is going to drive the car is the guy who is going to engineer the car? Maybe the driver is 18 years old and is named Max...

Brian

[bhamfal]

A good brake duct will reduce overall car drag, increase downforce directly on the tire where you want it the most, and let you run significantly smaller and lighter calipers and pads, for reduced unsprung weight overall and reduced parasitic drag from the pads on the rotors. That's if you design your overall system to require brake cooling ducts in the first place. How about designing the upright to run smaller and lower friction bearings that require cooling to survive? I've seen air cooled bearings in "big car" uprights.

The question still is what rules do they fall under. I still don't think they are part of the braking system.

Brian

If it produces down force is it not therefore illegal since it is attached to the part of the suspension that moves?

[Brian]

Deja-vu all over again, the past rears it's ugly head. That said, "If it produces down force is it not therefore illegal since it is attached to the part of the suspension that moves?" is exactly where I was going with that thought.

Brian

[Art Smith]

can anyone point me to one or more scientific papers examining L/D improvements from the use of brake ducts employed in proximity of tires on an open wheel race car? all of the papers I've read through the years have focused exclusively on drag reduction of the rotating tire/wheel assembly or the resulting interference drag on the flow field around the car's body. reducing tire width and/or height are the only mechanisms I've seen discussed for reducing lift of a rotating tire/wheel assembly as used on an open wheel race car AND clearly neither apply to FFord as there is now a spec tire.

it's important to remember it's a compliance question; not a "need" question or an "intent" question. at the core of the compliance question is a basic heat transfer design problem that rewards solutions with less weight, less rotating inertia, less rolling resistance, less aerodynamic drag, .........

Art
artesmith@earthlink.net

[Hardingfv32]

1) How would you prove a brake duct produces downforce?

2) In F1 where you find a constantly changing variety of brake duct designs... it is all about flow management and cooling. I do not think there has been any controversy about the creation of downforce on a non-sprung assembly.

Brian

[Art Smith]

1) How would you prove a brake duct produces downforce?

2) In F1 where you find a constantly changing variety of brake duct designs... it is all about flow management and cooling. I do not think there has been any controversy about the creation of downforce on a non-sprung assembly.

Brian

Brian-

thanks; 1000% agree with you! others have suggested "down force" and "movable aerodynamic device" concerns as potential problems; just attempting to keep an open mind doing proper due diligence in the determination of the facts. an objective process question only!

Art
artesmith@earthlink.net

[DanW]

Paddy Lowe explains below....

It appears a brake duct can serve more than one purpose, including downforce.

http://www.jamesallenonf1.com/2016/0...-of-f1-brakes/

[Art Smith]

Dan-

Thanks!! hadn't seen brake ducts with airfoils scabbed onto them before. pretty clear to me "airfoils" wherever they're mounted won't fly in FFord !!!!

Art
artesmith@earthlink.net

[chrisw52]

Paddy Lowe explains below....

It appears a brake duct can serve more than one purpose, including downforce.

http://www.jamesallenonf1.com/2016/0...-of-f1-brakes/

that's really cool... (pardon the pun)