Brake Pedal Box Mounting

[whiskeybusiness]

Hello to all,

My name is Elliot Carter, and I am a brakes team member with Warrior Racing at Wayne State University. I am in charge of designing the pedal assembly for our 2016-2017 season car, and I am exploring options on how to mount my design. In the past, adjustability has been a huge concern, leading some drivers to be forced to use a position that is less than ideal.

Improving the ease of adjustment for my design is one of my major design goals, and drawing inspiration from my job as a bike mechanic, I began looking into a design similar to the way that seat posts are secured into the seat tube of a bike. This setup consists of two concentric tubes, with a slot cut into the larger of the two and a collar providing clamping force to the pair. These systems seem to hold up to the repeated loading and unloading of bicycle riding with heavy riders, provide nearly endless adjustment, and are light when well executed.

My thought was to mount the brake pedal box in the same manner, with four caps clamping the base plate to the frame's rails. However, I am worried about the safety of this design. While under ideal situations, the clamping force of the two-bolt caps is sufficient for friction to resist the 2000N force laid out by the rules. However, will I run afoul of the design judges for having a braking component secured in such a manner? Any input would be greatly appreciated, especially from teams that have explored this or similar routes.

Elliot D. Carter
Brakes Team Member
Wayne State University
Detroit, Michigan, USA

[tdzanic]

Why not just bolt the pedalbox to a set of L-beams with mounting holes every inch or so? You don't need the continuous range of adjustability that would necessitate the bike seat idea, and it would be much more secure.

[whiskeybusiness]

tdzanc,

I appreciate you suggestion, and using through bolts is definitely something that was discussed for this pedal box. This method of mounting has already been created as a fallback in the case that the clamping system is not sufficient, however I was more looking for feedback about whether or not it is feasible.

Our brakes team is acutely aware of the traditional mounting options for brake pedal boxes, and I simply wanted to pursue a method that seems to be overlooked. The major advantage, outside of adjustment, is potentially being able to mount to the outer frame members without drilling holes and having to file an SES. This would eliminate the necessity of as many as three frame members dedicated to supporting the pedal box and allow for fine adjustment. What are your thoughts about relying on friction to secure such a component?

My primary worry is that a painted or brake-fluid contaminated surfaces might not provide a sufficient coefficient of friction, and the sliding of the box would provide a safety hazard to the driver.

-Elliot

[MCoach]

tdzanc,

I appreciate you suggestion, and using through bolts is definitely something that was discussed for this pedal box. This method of mounting has already been created as a fallback in the case that the clamping system is not sufficient, however I was more looking for feedback about whether or not it is feasible.

Our brakes team is acutely aware of the traditional mounting options for brake pedal boxes, and I simply wanted to pursue a method that seems to be overlooked. The major advantage, outside of adjustment, is potentially being able to mount to the outer frame members without drilling holes and having to file an SES. This would eliminate the necessity of as many as three frame members dedicated to supporting the pedal box and allow for fine adjustment. What are your thoughts about relying on friction to secure such a component?

My primary worry is that a painted or brake-fluid contaminated surfaces might not provide a sufficient coefficient of friction, and the sliding of the box would provide a safety hazard to the driver.

-Elliot

PM me. I know your teammates and that car very well.

[Charles Kaneb]

Whiskeybusiness,

I live 10 miles from Wayne State.

I'm willing to be the "go/no-go" tester for how much clamping force is needed on the pedal box. Please draw it up around a 500# force on the pedal - I'm a bit heavier than the average FSAE driver.

Clamping provides a far better stress distribution than a hole and bolt, so it'll be stronger, but the clamp itself may have to be beefy.

If you want a steady coefficient of friction, go bare metal on bare metal, use a seal at each end to keep most junk out.

[Charles Kaneb]

tdzanic,

Unless you mount it so that the force passes through the shear-center of the L-beam, they'll twist whenever you step on the brake.

[Charles Kaneb]

Any updates on this? If you'd like me to come down and check this out I can.

[whiskeybusiness]

We ended up going a different route with the mounting for weight savings, the pedal box will be secured with four quick-release Pit pins mounted in double shear. While not the most elegant solution, I found it to be the highest strength to weight ratio and provide the simplest means of adjustment.
I greatly appreciate you following up with me in this regard, I apologize for not getting back to you sooner.