PDA

View Full Version : Since we had so much fun with cam timing..how about Brakes



JeffYoung
09-20-2004, 11:49 PM
Here's a question. I'm having a b$%^h of a time keeping the tiny little pads, rotors and calipers on the front of my car cool. Ducting is free, right, as are modifications to the backing plate to allow air to reach the rotor, right?

So, I can I put on one of those "tophat" things I saw in Carrol Shelby's book on cooling solid discs that is basically an extension of the backing plate? It's basically a modification to the backing plate that directs air to both sides of the rotor....fire away guys, tell me what you think.

Jeff

Geo
09-21-2004, 01:42 AM
I think that's legal and it's exactly what I'm going to do.

"Backing plates and dirt shields may be ventilated or removed. Air ducts may be fitted to the brakes, provided they extend in a forward direction only and that no changes are made in the body/structure for their use."

Of course in another part of the ITCS it specifically allows holes of certain dimensions to allow for brake duct hose.


------------------
George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

JeffYoung
09-21-2004, 01:59 AM
Ok...one down, one to go.

Next potential "solution" I have looked at is a fluid recirculator. It's basically a check valve in the brake line that allows fluid to flow out from the caliper when I use the brakes, to be replaced by other fluid in the line, using a line coming out of the bleeder nipple.

I was real iffy on this one to start, but then I looked at the GCR. Brake lines are free, and I've seen all kinds of crazy spirals and other things in the lines on other people's cars, so would "brake lines free" mean I can put this check valve in so that I can get the hot fluid out of the caliper before it melts my seals -- as it has been doing on a regular basis?

m glassburner
09-21-2004, 02:12 AM
Is it brake fluid temp or rotor temp that is melting your seals?...the ducting should help with that....I'm wondering if blowers like sold at pe----- are legal??

[This message has been edited by m glassburner (edited September 21, 2004).]

JeffYoung
09-21-2004, 02:18 AM
Not sure. I don't think the fluid is boiling, but I can see the seals smearing across the piston. So, not sure what is getting "too" hot although I suspect the fluid is way above the melting point of the rubber seals.

I thought about the blowers but considered them definitely illegal -- nothing at all in the GCR about electric motors in your brake ducts. At least with the brake recirculator it is simply a check valve and additional brake pipes where brake lines are "free.' While I would like some that are more knowlegeable on these matters to weigh in, I think I at least have an argument here.

But we will see.

Geo
09-22-2004, 02:31 PM
I don't see how a check valve can be construed as brake lines.


------------------
George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

JeffG
09-22-2004, 05:00 PM
Wheel fans are legal.

apr67
09-22-2004, 08:35 PM
The seals should never touch the brake fluid, they are really 'dust boots'. (unless you mean the rubber brake pistion ring that some brakes have).

I am sure that the seals are burned up from the brake heat.

Alan

Ron Earp
09-22-2004, 09:30 PM
Don't know, but I'll make them for you. And, I'll put some peltier devices on there for you too, with big heat sinks. But what do I know, I've got adjustable cam gears I'll use too, so look out.

Bill Miller
09-22-2004, 10:05 PM
Have you used any of the temp-sensitive paint to see just how hot the components are getting?

------------------
MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608

Ron Earp
09-23-2004, 07:24 AM
Or stick a couple of thermocouples on there and we'll log the temp and figure out exactly what is going on. Might have to do that on a test day.

JeffYoung
09-23-2004, 02:46 PM
Alan, I don't use the dust boots, it is the rubber seal about 1/2 down the piston that is melting.

Ron, we'll take a look at it. Really annoying this problem.

George: just thinking out loud here, not really taking a position. How is the valve and additional lines any different from additional lines and a proportioning valve? Not sure that I see any real distinction.

Wheel fans are legal??

Quickshoe
09-23-2004, 05:08 PM
Per GCR 17.32 they are legal. Not sure how that affects the wheel width rule though....I'll stay out of that one.

------------------
Daryl DeArman

Geo
09-23-2004, 08:55 PM
Originally posted by JeffYoung:
George: just thinking out loud here, not really taking a position. How is the valve and additional lines any different from additional lines and a proportioning valve? Not sure that I see any real distinction.

Proportioning valves are specified as legal.

A check valve for recirculating brake fluid cannot be confused with a proportioning valve. I don't see any other way to slide the valve under the rules. It's not a line which is free. There is just no provision for it.


------------------
George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

lateapex911
09-24-2004, 12:24 AM
Jeff, I know where you're coming from...I've been there myself...but its a stretch at the very least. I gotta go with the guys here and say that adding check vlaves is beyod the scope of "brakelines are free".

The one phrase that caught my eye is the "brake circuitry may be revised", but adding lines and check valves is way more than revising.

And the proportioning valve sits in line..no added lines needed. The ITCS only allows pressure limiting P valves. (Which are limited in their use at the greater adjustment settings as they hinder the release of the brakes, making modulation difficult. (or so I read somewhere! )
Nice idea though!

------------------
Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

m glassburner
09-24-2004, 02:53 AM
Wheel fans are just a different type of rim I thought ?? Designed to help move air ...

apr67
09-24-2004, 09:29 AM
Wheel fans are sorta like hubcaps, and they extract air from the wheels.

They are specifically disallowed in the GCR for some classes (SS, SRF) if I remember correctly.

IT is not one of the restricted classes, again, as far as I can remember.

Eric Parham
09-25-2004, 01:27 AM
No opinion on whether or not checkvalves are permitted, but I think it should be possible to do fluid recirculation without any.

Idea #1: use a feed line with a larger diameter orifice at the master than at the caliper, and/or a return line with larger diameter orifice at the caliper than at the master.

Bill Miller
09-25-2004, 09:17 AM
Originally posted by Geo:
Proportioning valves are specified as legal.

A check valve for recirculating brake fluid cannot be confused with a proportioning valve. I don't see any other way to slide the valve under the rules. It's not a line which is free. There is just no provision for it.




George,

How about if it's incorporated into the brake line? Brake lines are free, nothing says what you can or can't do w/ them.

------------------
MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608

JeffYoung
09-25-2004, 09:35 AM
That was sort of my thinking, coupled with Jake's reference to the brake circuitry (aren't lines and valves and such what they are referring to here?) being subject to revision, that lead to me concluding it was legal.

I might write Topeka on this. Sort of one of those things in the gray area that certainly moves IT farther away from stock cars with cages and suspension to true race cars........

Geo
09-25-2004, 11:25 AM
I don't see any provision.

Lines are lines and valves are valves and people know the difference. I also don't see it being within the spirit of IT. But the spirit is secondary. Just don't see how it could slide under the rules.


------------------
George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

Bill Miller
09-26-2004, 04:53 AM
Originally posted by Geo:
I don't see any provision.

Lines are lines and valves are valves and people know the difference. I also don't see it being within the spirit of IT. But the spirit is secondary. Just don't see how it could slide under the rules.



George,

You're allowed to use AN line w/ AN fittings. A check valve is just another type of AN fitting. You're allowed to fit a remote oil cooler, or an Accusump. Doesn't say anything in there about explicitly being allowed to use check valves, but I bet everybody that's running an Accusump has one.


------------------
MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608

Ron Earp
09-26-2004, 07:00 AM
QUOTE=George,
You're allowed to use AN line w/ AN fittings. A check valve is just another type of AN fitting. You're allowed to fit a remote oil cooler, or an Accusump. Doesn't say anything in there about explicitly being allowed to use check valves, but I bet everybody that's running an Accusump has one."

This is timely as I was just looking at prices for the Accusump and was wondering about check valves. When I walked the pits at VIR I saw a lot of these things and check valves.

Therefore, seems that everyone I saw was running check valves on these things, despite it not being explictedly stated in the rules. By inference, one could do the same on brake lines.

Just my 0.02 cents from the newbie persepective. It is no suprise the SCCA doesn't have a lot of young members, going through the rule book is an exercise in patience when you have to read the rule, compare it to actual practice, and then worry about this "spirit of the rules thing". About like an Unholy trinity.

My guess is had I built (still building) my car on an island, with no internet or personal SCCA racer help, only the rulebook and my interpretation as a guide, my car would be quite different than the average IT car and, quite uncompetitive.

Greg Amy
09-26-2004, 09:13 AM
<font face=\"Verdana, Arial\" size=\"2\">...going through the rule book is an exercise in patience...like an Unholy trinity...had I built...with no internet or personal SCCA racer help...my car would be quite different...</font>

Ron, you are absolutely spot-on the first point. This is the kind of thing you will find in *any* large and/or older organzation, regardless of the industry. There will always be people within it that have been tehre for a long time, making and following rules for decades, and there will always be a partial "groupthink" and "the way things are" mindset. It's inevitable and expected.

Hell, consider, for example, relative newcomers Southwest Airlines and JetBlue's method of doing business versus Delta and American. total different mindset, total different culture.

However, I disagree with you on the second part. This same groupthink and midset can be a significant corporate ADVANTAGE when it comes to rules Take, for example, such mods as remote reservoir shocks, spherical bearings, and MoTec ignition systems in Improved Touring. Each one of those clever "advances" came from new people who read the rules and applied new technology. These items were never *intended* to be allowed and totally blindsided the "way things have always been done" crowd, but through the new perspective they were introduced and have become a competitive advantage. Some, such as the remote reservoirs, were eventaully specifically banned but others have prevailed.

I believe the true competitive advantage comes from both an open mind *and* the experience of time. Those that have that are the ones that advance through the ranks. You can and have gained some the experience via direct contact here and other places, but I encourage you to keep your newbie mind open to the possibilities out there that no one else has yet seen...

GregA

lateapex911
09-26-2004, 09:51 AM
I don't think an accusump (or similar pressure accumulation system) is a fair comparison...

The ITCS allows you to add that system to your car....it doesn't list what is and what isn't part of the system. Ergo, if it says you can, you can

However, the ITCS allows you to substitute brake lines and revise circuitry. In other words, you can revise the way the existing lines are run, but the word "add" isn't used and adding check valves and new lines to an existing system is beyond the scope of the provisions.

Ron...you're right...but some embrace the challenge of the rule book, and that it allows free thinking guys like my pal (and future ITA competitor... grand, just grand!) Greg Amy to solve some problems where others just read what they assume is there and leave items on the table.

It is in a constant state of evolution, and could probably use a rewriting as it is getting pretty patched....but considering the number of cars it covers, the complexity of the systems, the diversity of the systems, and the amount of time the category has been in existance, is is to be expected that there might be an issue or conflict or oversight here and there.

Eliminating 75% of the models that are classified would really simplify things, the rulebook would end up making more sense, be streamlined, and parity would improve, but then the charm of IT would be lost. So, I look at the book as part of that charm, kinda like an old car!

------------------
Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

Geo
09-26-2004, 01:13 PM
I'm in agreement with Jake on this one that the comparison with the Accusump is not the same.

Ron, kudos on reading the rule book with an open mind. I'd suggest writing to Topeka. Or you could run it until someone protests you and getting an answer that way.


------------------
George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

Ron Earp
09-26-2004, 01:53 PM
substitute [/i] brake lines and revise circuitry. In other words, you can revise the way the existing lines are run, but the word "add" isn't used and adding check valves and new lines to an existing system is beyond the scope of the provisions.

Revise, well....
----
Re*vise", v. t. [imp. & p. p. Revised; p. pr. & vb. n. Revising.] [F. reviser, fr. L. revidere, revisum, to see again; pref. re- re- + videre, visum, to see. See Review, View.] 1. To look at again for the detection of errors; to re["e]xamine; to review; to look over with care for correction; as, to revise a writing; to revise a translation.

2. (Print.) To compare (a proof) with a previous proof of the same matter, and mark again such errors as have not been corrected in the type.

3. To review, alter, and amend; as, to revise statutes; to revise an agreement; to revise a dictionary.
---
Key word being alter. Which, according to OED means:
al·ter ( P ) Pronunciation Key (ôltr)
v. al·tered, al·ter·ing, al·ters
v. tr.
To change or make different; modify: altered my will.
To adjust (a garment) for a better fit.
To castrate or spay (an animal, such as a cat or a dog).

Not so much of a stretch. But, we really shouldn't have to go through such semantics to build a car and follow the rules. George doesn't feel the Accusump comparison is valid, others do - just another example of how these things can be interpreted many different ways.

And a young fellow just asked me last night about racing in the SCCA, but I'll open that up on another thread because it certainly highlights some of the problems with our system.




------------------
Ron
http://www.gt40s.com
Lotus Turbo Esprit
BMW E36 M3
RF GT40 Replica
Jensen-Healey: IT prep progressing!

Geo
09-26-2004, 02:10 PM
Originally posted by rlearp:
Revise, well....

3. To review, alter, and amend


Indeed. Nobody is saying you cannot alter the circuitry. That is called out in the rules. The crux of the discussion is whether adding a check valve for fluid recirculation would be considered altering the circuitry or if it's simply adding a part. Also, another point for discussion/argument is the addition of lines for the recirculation and whether or not that would be legal.


Originally posted by rlearp:
And a young fellow just asked me last night about racing in the SCCA, but I'll open that up on another thread because it certainly highlights some of the problems with our system.

Unless your run a spec class there is no way the rules can cover all situtations explicitly, past, present, and future.

Again, it doesn't take much to send an e-mail to Jeremy.


------------------
George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

lateapex911
09-26-2004, 04:34 PM
Originally posted by rlearp:
To change or make different; modify: altered my will.
To adjust (a garment) for a better fit.

Not so much of a stretch. But, we really shouldn't have to go through such semantics to build a car and follow the rules. George doesn't feel the Accusump comparison is valid, others do - just another example of how these things can be interpreted many different ways.



Well, even in a spec series there are issues that come up like this!

Issues of definitions often require extra clarification.

To use your example, is adding an extra arm to the garment considered "altering"? I don't think so. Altering would be lengthening the existing arm, or adjusting the cut of the arm at the shoulder to improve fit, but an extra arm would result in a different garment

But, as always, it's just MHO... http://Forum.ImprovedTouring.com/it/wink.gif

------------------
Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[This message has been edited by lateapex911 (edited September 26, 2004).]

Ron Earp
09-26-2004, 08:23 PM
Don't know about garments. All I know is alter means "To change or make different; modify" per the dictionary. I suppose that adding a check valve and recirculation is altering, or changing or making different. It'd fit the letter of the law.

Ron

------------------
Ron
http://www.gt40s.com
Lotus Turbo Esprit
BMW E36 M3
RF GT40 Replica
Jensen-Healey: IT prep progressing!

Geo
09-26-2004, 08:26 PM
Originally posted by rlearp:
Don't know about garments. All I know is alter means "To change or make different; modify" per the dictionary. I suppose that adding a check valve and recirculation is altering, or changing or making different. It'd fit the letter of the law.

Ron



Altering is altering. Adding is adding and not specifically allowed in this rule.


------------------
George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

il8apex
09-28-2004, 07:54 AM
Guys-

I'll have to speak up on this one... It seems to me that a revision in the plumbing is allowed, therefore any number of T-fittings, elbows, and check valves would be okay in my book. However...

My (underqualified) technical opinion is that simply adding a check valve and a return line upstream of the caliper won't solve your heat problem. If you look carefully at recirculating braking systems they are designed to circulate fluid though the caliper itself and have fittings on the front and back of the caliper (before and after the piston as the fluid flows). That way the fresh fluid being drawn into the caliper is what actually cools the piston. In order for that to happen on an IT car with stock brakes you would have to modify the caliper, a definite no-no.

You'd have a far easier time of cooling the brakes with ducted air. The "top hat" solution is a time-honored and effective method. The cost to benefit ratio of plumbing a return line on the brake fluid would be way too large an investment (timewise) for my tastes.

My $0.02

-Tom

JeffYoung
09-28-2004, 08:11 AM
Tom, thanks for the thoughts. I'm going to duct the hell out of the thing, including a duct to the caliper.

By the way, the "recirculating" valve uses a line coming off of the brake bleeder screw, so no modifiation to the caliper required.....kind of neat actually.

Knestis
09-28-2004, 11:06 AM
Hey - it just struck me that I already have check valves in my calipers. Speed Bleeders. Am I in trouble? http://Forum.ImprovedTouring.com/it/smile.gif

K

m glassburner
09-28-2004, 12:43 PM
Oh s--- !! Don't go there http://Forum.ImprovedTouring.com/it/smile.gif

il8apex
09-29-2004, 04:46 PM
[openpandorasbox] Thanks, K! [/pandorasbox]

Mark LaBarre
09-30-2004, 06:21 PM
Some AS'ers tried this and were shot down. I was going to, under "the fittings are free" concept, but I was told by Denver (at the time) that because I was creating a device with the allowed fittings that was not expressly allowed, it was not legal
YMMV

ChrisCamadella
09-30-2004, 09:44 PM
While we're busy looking up words in our Funk & Wagnalls, don't forget the first rule of rule interpretation. The FIRST place you look up the definition of the word is in the glossary at the back of the GCR section of your rule book. If the word (or expression, in the case of more than one word) is in there, you use THAT definition. Otherwise, the F&W is fair game.

Cheers,

Chris Camadella
ITS Porsche 944S

ChrisCamadella
09-30-2004, 09:52 PM
I would like to compliment GregA for his wonderful comments above, just for the record...

On a more serious note, if your brake fluid is melting the piston o-ring, I think you need to radio Houston that we have a problem. It should not be that hard, on an IT car, to cool the brakes sufficiently unless you have a 240Z. Add the cans like it shows in the CS books. Add a gizmo that directs the cooling air into the eye of the rotor, if you have vented rotors. Get good brake fluid (I use AP550, but YMMV). Change it often. Make sure the piston isn't getting stuck. Don't rest your foot on the brake pedal while motoring down the straights. Don't brake so much!

Actually, lots of folks who are new to racing wear out the brakes. I did it myself. The problem is really that you brake too much, or too gradually, and that heats up the brakes. Racing is just like playing the piano. You just practice, practice, practice, just like the old joke about how you get to Carnegie hall.

Cheers,

Chris Camadella
ITS Porsche 944S

Knestis
09-30-2004, 10:17 PM
Originally posted by ChrisCamadella:
... It should not be that hard, on an IT car, to cool the brakes sufficiently unless you have a 240Z. ...

...or a wedge-shaped British sports car with a Buick V8. http://Forum.ImprovedTouring.com/it/smile.gif Chris might have missed that fact.

K

JeffYoung
10-01-2004, 12:03 AM
Kirk, thanks for making sure my precise (and self-chosen) dilemma is clear...lol.

Car is a 1980 TR8 that weighs more than a 240Z and has smaller pads and rotors (and nearly useless drums in teh back). I kid you not.

Chris, I hear ya. I do. Part of this is a driver issue. Last year I had no brake problems, but I was slow, and not really working the car. Now that I've gotten up to semi-speed, I am working the brakes much harder. And I need to learn to work within the parameters of what the car gives me. I've talked to a lot of people and we've run over the issue and over the issue and one thing is I do need to learn to brake less and more efficiently.

BUT..it is not like I'm resting on the pedal down the straights or braking for too long without much pedal effort. I've at least progressed past that point.

And, I'm using Motul 600, and just bought a can of that liquid gold Castrol SRF to try at Roebling next weekend. I've got Performance Friction pads and decent ducts and top hats. NOTHING is working.

I'm going to start carrying extra seals to races because I literally melt through the seals every race.

So, yes, Houston there is a problem and unfortunately Mission Control has not been able to come up with a solution.

But I'll keep working on it.

Knestis
10-01-2004, 12:21 AM
I'm worried that you may just have a thermodynamic deadlock on your hands, Jeff. If the rotors simply don't have the surface area to shed heat energy fast enough, additional ducting may not make much of a difference.

The fact that the seals seem to actually be melting is not evidence that the fluid is pooping out on you.

If you do add more ducting, point it at the caliper.

How about some NASA thinking here, maximizing lots of little advantages to see if they measure up to a measurable benefit.

** Bead blast your calipers to rough them up - marginally increasing surface area - then apply a heat-shedding coating?

** Add a thermal barrier between the pad and piston?

** Thinking outside of the box again, how about brake pads with heat sinks built into the backing plates?

How do the rears hold up? Are you using all of the rear brake that you have available, as lame as they may be?

K

Quickshoe
10-01-2004, 01:17 AM
Along the same lines as some of Kirk's comments.

A very smooth rotor surface does not have as much surface area as a "rougher" area. Don't know how much more agressive they would be on pads...never had the need to experiment that way. Heck didn't even need to duct my solid front rotors.

Perhaps someone with more knowledge than I can tell you how rough a surface you can tolerate before other issues arise.

Brake pads are free. Have you experimented with other brands?

How about wheels? Are there other styles of wheels that may allow more heat to escape? Is the problem worse with steel wheels versus aluminum wheels?

Good luck.

m glassburner
10-01-2004, 02:35 AM
Rims...we havn't talked about those yet....what kind do you use?

gsbaker
10-01-2004, 07:34 AM
Ducting is most effective when it maximizes air velocity.

A good friend is a mechanical engineer who does a lot of thermal work. He tells me the ability of air to remove heat from a surface varies with the cube of velocity.

Gregg

JeffYoung
10-01-2004, 12:32 PM
Guys, many thanks for the thoughts. I'll try to answer your questions below:

1. Bead blasting the calipers -- never thought of that. They are off, so I might as well try.

2. Insulation between pad and piston. Kirk, I tried metal shims. HATED the pedal feel and besides, it didn't work. Had someone suggest smearing silicon on the back of the pad as an insulator. Will try that. Question for you: I'm a lawyer, not an engineer. I just sue people, and don't have enough experience actually doing somehing useful like building things. What is a heat sink?

3. I have not tried temp sensing paint on the calipers to see what is getting hot. Good idea, and I will try that.

4. Rims are Panasport Ultralights. About as good as you can get weight, air flow and heat transfer wise I suspect in 13" size.

5. I will duct the caliper, I have not done that previously.

6. I just installed a proportioning valve to make sure I am using the rears (I've gone a season and a half without significant wear on the rear shoes). So, up until mid-summer, I was not using the rears enough. Now, I am using them just short of the point of locking up the rears, and I'm still have the problems up front.

7. Pads. I've run Hawk Blues and the PFC. Much prefer the PFCs. Have not run the BLues since I started having these problems, maybe I should. Have not tried Carbotechs.

Back to the woodshed this weekend. Fortunately, Roebling is easy on brakes so I'm hoping I can make it through the weekend without a melt through.

Thanks again guys.

Jeff

JohnRW
10-01-2004, 01:13 PM
Originally posted by JeffYoung:
I'm a lawyer, not an engineer. I just sue people, and don't have enough experience actually doing something useful...
Jeff

You guys ought to consider the wisdom of offering brake system modification advice to someone familiar with litigation procedures.

Some cars just have disadvantages 'built-in'. Unless we want a 'spec class', we'll all just have to live within the rules for fixed to the inherent problems.

Knestis
10-01-2004, 01:21 PM
I wouldn't put much trust in Si gel behind the pads. I was thinking of dense Si shim material. We had samples that we used under integrated circuits a long time ago in a previous life, that came in different thicknesses and densities. Translating theory into a practical solution here would take some poking around.

A heat sink is a device with lots of surface area, intended to shed heat energy to the surrounding air. Since pads are free, you could have a backing plate - space and caliper design permitting - that put some metal out in the airstream, to cool the pads before they could transfer that heat to the pistons.

It's good to know about the lawyer thing, by the way.

K

Tom Donnelly
10-01-2004, 05:27 PM
I use Hawk Black HT9 pads on my 240z. Ducts to rotors and calipers with a clamshell on the calipers (kinda like a tophat I guess).

And I have the pads riveted instead of just glued. The Blacks worked better for me than Blues. Brakes totally went away with the Blue. Still go thru rotors and pads and can have at least one 'Oh Shit!' per race.

Hawk phased out the HT9 so I'm going to need to find another. But that is what worked best for the 240.

Tom
'70 ITS 240z

Tom Donnelly
10-01-2004, 05:32 PM
Kirk,

I was real interested in the velocity statement. If you could run a venturi of sorts in the ducting somewhere, that would increase the velocity, right? Like, scale down the ducting and scale it back out and that might create a low pressure area just after the 'pinched' part? Or is the air flow too erratic in flexible tubing or too dependent on vehicle speed to matter?

Tom

I looked back and saw it was Greg who mentioned velocity. Sorry about that Greg.

[This message has been edited by Tom Donnelly (edited October 01, 2004).]

GKR_17
10-01-2004, 06:03 PM
Originally posted by JeffYoung:

6. I just installed a proportioning valve to make sure I am using the rears (I've gone a season and a half without significant wear on the rear shoes).

Where did you install the prop valve?

What compound pad have you been running from PFC?

JeffYoung
10-01-2004, 06:13 PM
Prop valve is right after the master cylinder. I have two lines coming out of the master -- one that goes to the backs, and one that comes out, "tees" and goes to teh fronts.

I put the prop valve in the engine bay because I figured it was one less thing the driver could screw up from the cockpit. Adjust in between sessions and leave it.

On the ducts and venturis...so if I narrow the duct down right before the rotors...I might increase the velocity of the flow and the efficiency of the cooling?? Neat idea.

JeffYoung
10-01-2004, 06:15 PM
Oh forgot -- compound was PFC 90, they've replaced it now with another compound..not sure what the new number is.

GKR_17
10-01-2004, 10:01 PM
I'll have to check that shape to be sure, but it has probably been replaced with 97 compound - and is a lot better for IT than 90.

I should have been more clear with my question on the prop valve, what I meant was which circuit is it in? All it really does is limit pressure (while also causing some pretty nasty hysteresis). So if you don't have enough rear brake now, you don't want to add one to that circuit. And it's not a good idea to have one in the front circuit either.

Grafton

Mark LaBarre
10-02-2004, 09:58 AM
Originally posted by JeffYoung:
..so if I narrow the duct down right before the rotors...I might increase the velocity of the flow and the efficiency of the cooling?? Neat idea.


Whilie the velocity may go up, you'll have a reduced volume of air due to the restriction. I'd opt for more volume any day for brakes.

gsbaker
10-02-2004, 03:26 PM
I checked with my ME friend and discovered I was wrong: the power needed to move air, not the ability of air to extract heat, varies with the cube of velocity.

(We were discussing this one night during one of several recent hurricane parties here in central Florida. Alcohol was involved, which probably explains my error.

How geeky is that? "Hey, let's have a beer and discuss fluid mechanics!")

In any event, it turns out that Mark is right and velocity matters. Long story short, increased velocity improves heat extraction if all other things are equal but, as Mark mentioned, if you choke down the duct too much you begin to loose volume.

Sounds like a little is good and a lot is bad. I'll ask around more on this.

Gregg

JeffYoung
10-03-2004, 09:02 AM
After pulling the calipers apart for the upteenth time, I decided to actually pay attention to what I found. Looks like the inside seal (meaning the seal on the inboard piston) is the only one that is failing....ducting to the caliper on the inboard side may solve this.

Ron Earp
10-03-2004, 10:01 AM
I know that seal was crispy, but you might want to use those dust seals too. If a piece of crap gets between the piston and bore it'll cause the seal to fail in short order, in many cases.

eh_tony!!!
10-03-2004, 08:56 PM
One guess I have is that the PFC pads are magnifying a marginal situation into a large problem. PFC pads tend to be very hard on rotors and generate high temps. We used crack a set of front rotors per race (and that's with a 6" duct and water spray) until we switched to the mintex.

Since your rotor/drum situation is marginal anyway, you may want to try something less aggressive (like a hawk black instead of blue).. Kind of an endurance pad with a lower torque.

Ducting to the calipers does make a big difference though

apr67
10-04-2004, 11:02 AM
One other option.

Heat shields. Prehaps out of stainless. Bascialy a thin sheet of metal in the exact shape of the backer plate on the pad to discourage heat from travleing into the pistion. I belive it to be legal, because it is just an extension of the pad, a shim if you will.

gsbaker
10-04-2004, 11:46 AM
Update on ducting:

Yes, it helps to increase the velocity by reducing the area, but not too much. If I find the magic number I'll post.

Gregg

Prince Makaha
10-17-2004, 02:43 PM
Originally posted by grega:

Hell, consider, for example, relative newcomers Southwest Airlines and JetBlue's method of doing business versus Delta and American. total different mindset, total different culture.





Actually Jet Blue and the other newcomer's advantage is that they don't pay out hundreds of millions of dollars a year in pension because they haven't been around long enough to have pensioned retirees.

That will change in time and my prediction is that regulation will come back lest the industry become unsafe as corporate entropy kicks in.



[This message has been edited by Prince Makaha (edited October 21, 2004).]

shwah
10-26-2004, 10:00 AM
OK so what happened to the wheel fans in this discussion? They are certainly legal, and they can move a large amount of airflow over the caliper, rotor and bearing housing. They also remove air from under the car. Lots of advantages here IMO.

They are allowed specifically per the GCR. They are not part of the wheel width, as they are not part of the wheel (removeable). I know that at least one ITA VW used to run them in the early 90s.

Just wondering why now we are only discussing the ducting options. Possibly the availability, or difficulty to fabricate wheel fans?

Chris

Tristan Smith
10-26-2004, 11:17 AM
I know, a total hijacking.....sorry.

"Actually Jet Blue and the other newcomer's advantage is that they don't pay out hundreds of millions of dollars a year in pension because they haven't been around long enough to have pensioned retirees.

That will change in time and my prediction is that regulation will come back lest the industry become unsafe as corporate entropy kicks in."

AND most of the new airlines don't have to pay the same landing fees as established airlines, and many times they have their plane lease costs deferred up to two years. Many predict that the future of all airlines will be roughly a ten year run, before they have to file for bankruptcy because their costs "catch up with them".

Having to watch my wife take her third pay cut as a flight attendent in 10 years I think that some basic regulatory action needs to be put into place. In most cases it is now cheaper to fly across country than to drive or take Greyhound. And my wife still has to listen to all the passengers bitch, whine, and moan about everything!



------------------
Tristan Smith
Buffalo's Southwest Cafe
ITA Nissan 240sx #56

JeffYoung
10-26-2004, 01:19 PM
It is an interesting situation, possibly without a solution (like my brakes). We tried regulation for nearly 50 years and it seemed to work. We junked that, and initially it seemed to work.

But now, it just looks like the existing economic model for airlines doesn't work. Costs are too high and revenues too unpredictable and on average too low.

I think you hit the unfortunate nail on the head. The discounting and other incentives given to non-business travel are probably going to have to come to an end. Air travel has been artificially cheap for nearly two decades, and that probably has to stop.

Interesting economic dilemma.

OTLimit
10-26-2004, 10:27 PM
I just look at the airline situation and sigh. They keep asking for concessions from the pilots, attendants, and mechanics, (and getting them, because everyone figures it's better than no job at all) but we never hear anything about the top executives giving up any of their pay, and they're making alot more than the ones giving the concessions.

------------------
Lesley Albin
Over The Limit Racing
Blazen Golden Retrievers

Geo
10-26-2004, 10:59 PM
Originally posted by Tristan Smith:
...many times they have their plane lease costs deferred up to two years.

I am not a CPA dealing with the airline business, but as an accountant, I'm am 99.99% confident what we are talking about here is a deferment of payments. This is NOT the same thing as cost. The costs must still be recorded despite the fact no payments have been made.


------------------
George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

lateapex911
10-26-2004, 11:01 PM
Originally posted by OTLimit:
I... but we never hear anything about the top executives giving up any of their pay, and they're making alot more than the ones giving the concessions.




The classic ENRON situation....of course those guys screwed their people willingly and knowingly, but really, isn't America famous for overpaid executives who get all the free perks, and still make bonuses even when the company goes under??

When was the last time we heard a top executive say that his companies big guys were all going to take a 15% cut in base and bonus? Maybe I'm just hearing all the (negative) headlines!


------------------
Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

Eric Parham
10-27-2004, 02:52 PM
Note that the caliper is partially insulated from the piston by the fluid as well as by the problem seals themselves. Ducting may remove heat from the caliper, but keeping the heat away from the piston in the first place seems to be the main requirement here (unless the problem rubber seals can be replaced with something having a higher melting point, maybe silicone -- my guess is that the British rubber is more natural than other possible sources).

Pad insulating shims have been discussed. The shims must be heat insulators (like ceramic) rather than heat conductors (like metal, and maybe carbon -- can someone check me on that? -- it's been nearly 20 years since RPI engineering school).

You might also consider the heat transfer properties of the pad material itself. In your particular situation (piston seal heat failures), you should probably try a pad material that is *not* a good heat conductor. Thus, choose high ceramic content rather than high metallic content.

Just some race-only advice from one lawyer to another. http://Forum.ImprovedTouring.com/it/wink.gif Cheers!

Eric Parham
10-27-2004, 03:34 PM
Originally posted by shwah:
OK so what happened to the wheel fans in this discussion? ... Chris

I've never tried them, but I did know someone who tested them on a World Challege Corvette. They tried pulling the air from the inside as well as pulling the air from the outside. The unacceptable (to them) disadvantages were that the wheel fans caused huge aerodynamic drag at higher speeds, cooled the tires more than desired, and didn't cool the brakes enough at lower speeds. Sort of like the non-linear boost problems of a turbocharger versus a supercharger.

gsbaker
10-27-2004, 03:55 PM
Originally posted by gsbaker:
[B]...If I find the magic number I'll post.[B]

Since this subject has been revived...

There is no "magic number" for reducing the area of ducting to increase the velocity in an optimal manner. However, there is an equation that requires measurements from flow meters and pressure sensors, but I don't believe anyone wants to go that far.

When I complained to my ME friend that this was becoming too complex for the weekend amateur he said, "Look at the end of a leaf blower. That's about right."

He also reminded us not to miss any hot surface area, e.g. if you can get to, say, 12 square inches of hot material you wish to cool, don't pinch the duct exit area down to less than that.

Now where is that leaf blower? http://Forum.ImprovedTouring.com/it/smile.gif

Gregg