Mounting disk brakes to CV's

[JCMarshall_law]

Anyone done it or thought about it?

I've seen a graph of CV life vs temperature - things started looking bad after about 100 deg C.

Here are a few quick ideas to combat the heat transfer problem:

1) lots of drilling of the rotors - both on the braking surface and closer to the CV,
2) Some sort of insulator between the disk and the CV (something similar to asbestos).
3) High temp grease in the CV's.
4) If all else fails - lots of front brake bias http://fsae.com/groupee_common/emoticons/icon_smile.gif

It would make things even simpler in the drivetrain (currently there is a solid spool rather than a diff).

Most formula SAE cars have very little CV angle anyway so the CV's are not generating a lot of heat of their own. The wear is minimal as well, CV's in FSAE cars are close to fixed splines if the drive line is straight.

I sure the judges would wet themselves when they see it, but if someone does the numbers and knows how to sweet talk the judges, then I think it might not be such a bad idea.

Has anyone else had any experence?

[Colin]

We ran our floating rotors on our CV's last year with no problem but we were using Aluminum MMC rotors that, due to the pad we use, do not generate huge amounts of heat and the heat that is generated is dissipated very quickly from the rotor.
http://www.hed.swin.edu.au/ses/fullboarracing/Acar27.png

[Daves]

A reliable source once told us that Formula 1 cars once used inboard disc brakes with the brake rotors sandwiched between the CV and drive flanges. There were few, if any, CV overheating problems.

This year we have brake rotors mounted to our rear CV joints, as shown on the following webpage: LeTourneau Suspension 2004-05 (http://www.letu.edu/opencms/opencms/_Academics/Engineering/engineering/student-projects/formula/teamsuspension.html)

For us, the dilemma was either to mount a single inboard rear brake to the differential or to mount dual "midboard" rear brakes to the CV joints. This year we do not have the time or resources to study the negative effects of braking on the differential. Also, we found some high temp (up to 500?F) CV grease (http://www.redlineoil.com/products_coolant.asp?productID=54). Therefore, we decided to go with the dual midboard brake design. Also, since the brakes are midboard, they will get better cooling than if they were inboard.

[JCMarshall_law]

500 deg F (260 deg C) CV grease sounds good, as far as I know, that is the problem with high temp CV's, the grease breaks down.

The rear disk was only getting up to 200 deg C at the pad surface on the UQ 2003 car, so with the other heat transfer fixes I mentioned, I think Disks on CV's may be worth having a further look at.

[rjwoods77]

Not that it really matters to us but they stopped doing that on cars because you would have no rear braking if a half shaft broke. Just an interesting "Jaguar learned the hard way" tidbit.

[Denny Trimble]

Actually, I think the move from inboard to outboard rear brakes in F1 and CART was done for aerodynamic reasons. Space inside the wheel is free aerodynamically, but raising the diffuser where the inboard brakes would be is worth a lot of downforce, I'd bet.

[rjwoods77]

Hey Denny,

Just talking streetish cars but that is the way more valid reason for doing it. Funny thing I saw at the vintage races at the Glen. Some protoype car had is lower wishbone in line with the halfshaft for that reason. Geometry looked like it suffered but you should have seen the diffuser? tunnel. I could almost crawl in it. I think it was a toyota powered prototype. At ground level(your head) you could see the 2 tunnels go all the way through. A twelve year old could have crawled through them.

[fsae racer]

Colin, maybe I'm blind, but where is your rear toe constraint? Also, how the heck did u guys get that thing so high on 2 wheels? Back on the topic of cv mounted rotors, we have had inboard cv mounted rotors on both the 2003 and 2004 cars, and the 2005 car is the 1st to allow the rear rotors to float. None of the old cars had any problems with overheatings cvs. These cars just dont weigh enough or go fast enough to generate that much brake temp especially in the rear. I dont think you could get a commercially available caliper to fit on a rotor small enough to over heat your rear brakes and still bolt it to a cv housing. As for drilling holes, I dont know why you want to do that, and the insulator, thats easy, use stainless for the go between to make your rotors float.

[Colin]

the rear toe controll is on the bottom wishbone towards the front of the car, they just happen to be hidden by the drive shafts in that photo. I don't understand your second question though?

[fsae racer]

at ur ecodive site, there is a pic of ur 2003 car on 2 wheels. wtf mate? doesnt look like anything is around the car, just too much grip?

[Colin]

very grippy tyres and a track width on minimum limit of the competition gave that car a tendency to lift wheels. by the time we got to the comp we had sorted it out but it would still occasionally lift inside front wheels. We had the car higher than that before that photo was taken but we never put it on it's lid and we never hit a cone or had an off course when it happened, it was a pretty weird car to drive actually

[Dan G]

dizzamn!

http://gtv.ecodive.org/images/2003/DSC00207.JPG (http://gtv.ecodive.org/FBR2003.htm)