How is brake test done? we r first tym team..

[satbat7]

how is the brake test exactly carried out at the event.. can anyone please explain in detail.. i have heard many teams fail to pass it..
thankz.

[satbat7]

how is the brake test exactly carried out at the event.. can anyone please explain in detail.. i have heard many teams fail to pass it..
thankz.

[John Grego]

At the event they set up fairly short course for you to perform the test. I would say you only have about 20 feet to accelerate before you have to lock up your wheels. The other challenging thing is that the judges don't always see them lock up. In 2005 we had 4 flat spots on our tires but one judge decided that he didn't see the wheel lock up. But that's the beauty of the competition!

Hope that helps

[kwancho]

It's decently well laid out in the rules. Brief acceleration, up to about 40-60mph, then slam on the brakes. There are judges looking at each tire to note whether it locks, and you've got to lock all 4 to pass.

[HenningO]

I wouldn't say 40-60 mph, at least not in Germany and England, more like 20-30 mph...

[John Grego]

There is no way you get can get up to 40-60 mph. Not in the amount of room they give you. You'd be lucky to make 20. Can you imagine what would happen if they let you get up to 40 mph, you slam on the brakes, and 1 wheel or 1 side didn't lock?

[kwancho]

I stand corrected. Thought it was a 75m acceleration length, but having seen it at West, it's clearly shorter than that.

[Steve Yao]

People try and treat the brake test as an accel run and it simply is not necessary. Unless you have significant aero going on, you can lock your brakes at 5mph as well as you can 20mph. And if you do have aero, its only easier the slower you go.

People don't pass brake test for one of four reasons.
1) They don't pass noise (both brake and noise are done in the same area)
2) The driver did not know what he was doing.
3) The braking system was designed poorly.
4) Brake system was improperly maintained.

-Most teams don't put significant effort into their sound attenuation. Understandable since it is not scored, but it can/will bite you in the @$$.
-Some drivers over think the test. This is not acceleration. This is not stopping on a dime. Accelerate modestly and jab on the brakes hard and fast. Even if the brake balance has not been set well, you can fool the scrutineers if you make them all lock fast enough. Like many student designed issues, it can be solved with a judicious application of force.
-Braking system poorly designed. There is almost no getting around this. I've seen cars built with kart brakes. They simply could not generate the line pressure and friction to lock all the wheels. If you are close, I've seen teams mount the rain tires and roll their car thru a puddle right before going into the test.
-Brakes improperly maintained. Most likely improperly bled(air in the lines). Too much deflection of brake or pedal components...or pedal tray improperly secured. Basically anything that limits how much line pressure can be generated.

[Ehsan]

The rain tire trick won't work. If the track is declared "dry" you cannot run rain tires. If you do, then you had a judge who was sleeping on the job.

Better trick is to overinflate the hell out of your tires. They bulge up, reduce the contact patch and lock up easier

[Big Bird]

You could always interpret the abovementioned "rain" tyres as being those used tyres that you "accidentally" left out in the rain and the snow for three months until they were rock hard and had no grip. In all seriousness you are not going to use your nice new tyres in the brake test, so you might as well use the oldest and least useful set for the scrutineering stuff. Use it to your advantage.

Anyway, if you have a really lousy braking setup, no amount of trickery is going to help you.

[satbat7]

our team made a low budget prototype and i found that flexing is a major problem.. one could loose tremendous amount of pressure wid even a millimetre of flex.. so rigid is a way to go,,

[mangel83]

Steve, although brake test is not an acceleration run the scrutineers made us take the brake test 3 times, even though we managed to lock the wheels in the 1st and 2nd run. They told us that they had to make sure our car would sustain the stress of hard braking after hard acceleration. So each run was faster than the one before. The last run was just a fast as the acceleration event.

[Steve Yao]

Manuel,

This was in Detroit? Fontana? or Brazil? other?
I had not heard of that being asked before. At least at the FSAE and FSAE West, that is not standard procedure. But final say is up to the scrutineers. My guess is they saw something in the 1st 2 runs that they wanted to be sure about...Perhaps trying to avoid what occured in 2005(?) when a car lost both front wheels/uprights when braking at the end of the accel run.

[mangel83]

Detroit

[terra_dactile]

Hi all,
Seeing the amount of people worried of passing the simple brake test, it makes me wonder how much design goes into your compnents selection, I was able to do fairly well last year at Detroit and California in the Contintal teves Best in class brake system awards, so if anyone has any specific question of brake design i would be more than happy to help where i can, as long as it make the car competiting near us be less of a safety hazard during the endurance race.

sincerely,

Jude Berthault
ETS FSAE 2003-Curent
Vehicle Dynamics Leader

[Nitesh]

At the UK competition also, they made us accelerate harder and harder. They would say that the brakes locked but we weren't fast enough.

[57JoeFoMoPar]

We had a hard time with the brake test in Fontana. All 4 tires would lock every time, but 1 might roll a 1/2 a turn before the car would come to a full stop, they failed us for that.

How we passed: put our lightest driver in (130 lbs), 35 lbs or air pressure in the tires, 8000 rpm clutch drop, full throttle to top of 1st gear, STAB the brakes hard (don't ease into em)