Brake Pedal Fixes Project
- Ahnaf Mamun
Tasks to repair MSXV brake pedal
What skills you can gain: Nodal Diagram, Mechanical Design, Solidworks solid modelling/assemblies, Rapid Prototyping (3D-printing), Machining, FEA (possibly), manufacturing/assembly, part sourcing
Project Information
Motivation
Our brake pedal for MSXV was functional…or was it After attending FSGP 2024 and while manufacturing/integrating our brake pedal for MSXV a variety of different problems were found - some of which being simple quality of life deficiencies and others larger functionality issues . Regardless, we want to fix all these issues for MS15.5
What are the (fixable) problems?
1. Floor-panel mounting
Our brake pedal in MSXV was mounted to a composite floor panel which was not manufactured to be able to retain the force of the brake pedal. This caused the the pedal to fail when depressed due to force not be transmitted to the master cylinder. This problem was heroically solved by Jens at competition by using a tensioned cable around the master cylinder mount attached to the chassis. This is less of a task for this vehicle, the solution for us would be to mount the brake pedal to a sheet metal and use that as the floor panel.
2. Limit Switch Integration
In our brake pedal assembly one requirement is to integrate a limit switch (basically a button) that's purpose is to activate the brake lights. So, when the pedal is depressed, the limit switch will activate/deactivate causing the brake lights to turn on. The current limit switch mounting solution is in an awkward position for the driver, as the pins of the limit switch are facing the drivers foot so if they stomp on the pedal there is a risk that the limit switch gets damaged. Moreover, if we change the pedal angle we will also have to change the limit switch mount.
Limit Switches are simple mechanically and electrically which provides an easy solution, example of one below:
3. Pedal Angle
Our current brake pedal has an arbitrary starting angle of 10 degrees forward. However, this is a major quality of life issue for the driver because the pedal is pointed towards them.
Project Description
As mentioned above, since there are multiple issues with our brake pedal we will split the overall project of fixing the pedal into two tasks with smaller sub-tasks. These tasks should be completed sequentially, as in without doing the first task (the angle change) you will not be able to do the next. Each task lends itself to the other which makes this fun
Task #1: Angle Change
Before we change the angle of pedal we want to see what this alteration will change within the entire system to do this we will create a nodal diagram!!
Nodal Diagram:
This part of the process is most likely foreign to most people, my old nodal diagram for the pedal will be available to you and I can always walk you through how to get started whenever (during dynamics meeting, or ping me on discord in dyn-brakes and we can call or message).
Results we want from nodal:
What angle is the most optimal to change to (see what will happen if pedal is at 90deg, or pushed back 5deg)
Find out if we master cylinder mount spacer box has to be increased/decreased in height
The master cylinder cylinder mount spacer (green) is a sheet metal part underneath the master cylinder mount (blue) thats purpose is to place the master cylinders at a height where the push rod (yellow threaded piece) can fully be depressed. As you can imagine, without the green box the intial angle of the master cylinder push rod would be too harsh causing for it not to reach its full stroke.
Approximate a number for the absolute limit of our pedals depression (when does our pedal max out), with this check for interference
Important Info for Nodal:
Our Master Cylinder:
The current master cylinder is our car is the Willwood GS Compact Integral Master Cylinder:
Key info:
Note that the stroke of the push rod is 31.8mm (1.25in)
Previous Nodal Diagram:
The previous nodal diagram is included in the google drive folder under resources, here is a screenshot for a quick idea:
Master Cylinder Mount Spacer:
Based on the nodal diagram you created you may or may not have found an initial angle that is beneficial for the master cylinder push rod and subsequently a height that the master cylinder mount has to be for this angle to be achieved. Now you can create a spacer that matches the dimensions of the master cylinder mount above it.
Assembly Update:
Now that the new pedal angle is locked with the new spacer, all that is left is to update the brake pedal assembly with the new changes. It is up to you if you want to make a copy of the existing assembly and alter it, or if you would like to create your own assembly from scratch.
Task #2: Limit Switch Mounting
The purpose of the limit switch in our brake pedal was introduced earlier (here). Essentially, we need a mount that will house the limit switch in a position where when the pedal is depressed the limit switch is deactivated.
Requirements/Design Notes:
Design MUST be adjustable (e.g bolt holes are slots rather then holes)
When we place the limit switch in the car some adjustment is required to get it positioned in a spot that works
Use fasteners to mount limit switch housing rather than adhesive or hot-glue
Ideally the limit switch will also use fasteners to attach to mount
Add limit switch into Brake Pedal nodal diagram to find out how far the pedal needs to depress for limit switch to activate
Part will be 3D Printed
Limit Switch Selection:
If your design requires a limit switch with a different stem/actuation point you can source your own on digikey. It may be helpful to scroll through some limit switches to see what is possible.
Previous Design:
Resources:
Brake Pedal files!
https://drive.google.com/drive/u/1/folders/1y2rKTnfzv5scxDThDmj0I1KaqP0ifbOb