Single Brake Caliper in Differential

[Phil1988]

Hey guys,

got a little question about the braking system. Our team thinks about a single brake caliper in the differential to safe wight.

Does someone of you have some experience with this system? Problems with braking at the braketest or so on?

Would be great to get a answer http://fsae.com/groupee_common/emoticons/icon_smile.gif

Regards Phil

[FStotal.com]

+
-> unsprung wheight

-
-> think about the question what happens when you drive in corners and brake
-> be aware of the forces in your driveshafts

[Matthew Newman]

We did this with our 2002 car. I guess having a single rear brake calliper may make it easier to package. On the other hand, you need to think how this will affect the drivability of the car (see the forum at the link: http://fsae.com/eve/forums/a/t...00868/m/94220973151) (http://fsae.com/eve/forums/a/tpc/f/332600868/m/94220973151)). It depends on a number of factors, power of engine, materials of drivetrain, suspension, tyres, etc.

[Racer-X]

It depends on how the car is set up as a whole.

If you are going for the really light weight single approach I can see it working out. You have less mass to deal with and the corner speeds are closer to the straight speeds, so you have less momentum to "fight". You won't need much rear brake. This should minimize forces and the effects of the uneven braking.

I don't think this would be a good idea in a heavier 4 cylinder car that needs a lot of brake and will be feeling the effects of the diff in the braking.

[Francis Gagné]

The UQTR guys had some trouble this year at the braketest in Michigan. It's not that the brakes were not working properly, but the scrutineers did not knew it was on the diff. So when they saw wheel movement they turned them down (One wheel was going forward and the other backward the other side). They had to go talk with an official and return to the brake test a second time to get their sticker.

Not much a design issue, but to keep in mind when at the comp.

[Claude Rouelle]

Think about the braking energy which will go in one caliper instead of two. Ask Oregon state / GFR why they went away from a one caliper solution.... They lost FSG because of that a few years ago.

But mainly make simple FBD and think how you diff works in braking and corner entry when you have one brake disc only on one side... or the other.

[Crispy]

Originally posted by Claude Rouelle:
Think about the braking energy which will go in one caliper instead of two. Ask Oregon state / GFR why they went away from a one caliper solution.... They lost FSG because of that a few years ago.


We ran a single caliper on our diff in 2009 and 2010, and it did cause us a lot of headaches, most of which can be attributed to the caliper choice. The caliper was from a mountain bike (Hope Moto v2) and we used its associated rotor as well. The setup was capable of providing the desired brake torque, but the issue we ended up with was that the pads would not last an entire endurance, which meant we had to run our bias significantly forward in order to make the distance. In 2010 we thought we could solve the problem with with different pad materials, but we could not find a material that met our needs. At FSG 2010 we went too aggressive with our bias, the pads wore down to the steel, the brake fluid boiled and the over travel switch was tripped. After 2010 we were all pretty much fed up with it and decided to just run a conventional setup (simple, easy, problem solved). All that being said, a diff brake should be just as reliable as conventional outboard brakes if sized appropriately.

As far as vehicle dynamics is concerned, I haven't been convinced that there is anything inherently bad about running an inboard brake on the diff. You just trade one group of problems/advantages for another.


Originally posted by Francis Gagné:
The UQTR guys had some trouble this year at the braketest in Michigan. It's not that the brakes were not working properly, but the scrutineers did not knew it was on the diff. So when they saw wheel movement they turned them down (One wheel was going forward and the other backward the other side). They had to go talk with an official and return to the brake test a second time to get their sticker.

At the brake test, all four tires need to lock. I would not expect special treatment just because of a differential brake set up. If a team got special treatment they should consider themselves lucky unless they received a clarification before the event. We always locked all four, which to do reliably, requires some amount of torque bias.

[Warpspeed]

If you plan to run a spool, or something other than a fully open diff, the whole rear braking left/right bias situation can change rather a lot.