quote:

Originally posted by RBbugBITme:
Are you saying that the design DART-CG has described to have worked for 2 years on his car, won't work?

I don't think he is saying *that* at all.
It will work, I think everyone has seen a similar design for the sake of packaging around comp.

He's saying there are some (oft serious) issues in having such a massive rising rate setup for your brake pedal.

Its up to the individual designing it to decide if the trade-offs in packaging benefits outweigh the drive-ability and ideal function of the pedal box setup.

Personally, I think there are much better ways to package the cylinders such that you don't get such a massive rate increase over the travel of the pedal. And still have the desirable "shallow" pedal-box profile.

I never said it doesn't work, but its a lot harder to get everything to work properly. DART-CG, do you suffer any long pedal issues during driving - any pad knockoff would cause a major problem??

I think a little too much fearmongering from Stretch here.

As people have pointed out it works. I built a vertically orient MC setup for U of Washington starting in 2006. The system has a falling rate pedal ratio of 4.33 to 3.92 at 20 degrees of pedal motion. So thats 10% increase in driver input required to maintain lock-up at 20deg of motion. We never see 20 deg of pedal motion and what force variation there is, is well within what a driver can deal with.

Honestly, our team did have some difficulty bleeding the system, but I've also talked to teams who have had no problems bleeding. Must be something we were doing wrong. You do not need to utilize the full stroke of the MC to bleed them...at least not with the Tilton 77.

It was mentioned that the varying in real-time bias can be pretty alarming. As i understand it, the rear-pivot MC and accompanying trunnion balance bar were created exactly to combat this by reducing friction/stiction(as Jude pointed out).

There were 2 reasons I implemented this:
1) It reduced pedal tray length by 4"
-4" less chassis tubing x 6
-4" less brake, brake bias, throttle, and electrical lines.
2) Brake pedal now in tension/compression instead of bending

Some cons:
-These MC's and the trunnion balance bar are expensive even with FSAE discounts.
-If for any reason you are not at 50:50 bias, the fixed pivot position of the trunnion bar mean that the MCs will put lateral forces into the brake pedal.

Re: Other short pedal box methods
Placing MCs above, below, or in between the driver's legs each presented issues with compliance or safety in my mind, but teams do them all.

3.2.5: In side view, no brake components on the sprung part of car can project below the bottom of the frame or tub.

from the 2009 rules change summary.

quote:

Originally posted by Michael Palaszynski:
3.2.5: In side view, no brake components on the sprung part of car can project below the bottom of the frame or tub.

from the 2009 rules change summary.

Yes, one of the reasons we made a switch from the 75 series to the 77 series was to package the pedal assembly above the lower rails. It also is a much simpler setup for us and we can now make use of a brake proportioning valve...