List of Components

1. Tires

Perhaps the single variable with the largest impact on stopping distance, the tires are always the limiting factor on the ability to comfortably stop a moving vehicle vs. uncomfortably slide uncontrollably into the nearest object. Assuming no slip, it is generally agreed that the tires are rotating at a fixed speed in revolutions per second that is equal to the speed divided by the diameter*pi. This is will be important for calculating rotor speed. The tire and its resulting coefficient of STATIC friction (remember, we want rolling, not sliding) between the surface are what will limit our maximum achievable braking acceleration and thus braking distance/time. 

Important variables: Coefficient of friction between tire & road

2. Rotors

The next component that will be featured on the car is the rotor. The rotor is generally a cylinder that has been attached to the axle. The cylinder rotates with the same radial speed (revs/sec) as the wheel and tire. 

Important variables: Coefficient of friction between pads & rotors, rotor diameter, contact patch between pad and rotor

3.  Pads

The brake pad is generally a steel plate with some type of friction material (normally some type of composite) laid on one side. The pad is held in a position by the caliper where, at 0 input, it does not touch the rotor and allows the rotor to spin freely. As pressure is applied through the caliper and the pistons contract (see below), the pad is forced against the spinning rotor and causes friction to occur. The energy from the spinning rotor is converted into heat, and as the rotor loses energy, it slows. As a basic kinematics question would demonstrate, the magnitude of the frictional forces are directly proportional to the force input, or, how hard the piston is clamping the pad against the rotor. This allows for variable braking (i.e. when you lightly tap a brake pedal, the vehicle responds by coasting to a stop, whereas if you step on it aggressively, the magnitude of deceleration is much higher, and your head bounces off the steering wheel).

Important variables: Coefficient of friction between pads & rotors

4. Calipers

The caliper is what holds the rotor in place. As previously mentioned, they generally contain a number of pistons that can expand and contract based on the fluid pressure in the caliper. This is used to apply a force to the pads and generate friction. On one side of each caliper, there is a pipe fitting that connects to the brake lines.

Important variables: Coefficient of friction between pads & rotors

5 Brake lines

Brake lines refer to flexible hoses that are attached to the master cylinder (see below). They contain brake fluid which allows for compression of the master cylinder to be translated into pressurizing the caliper. 

Important variables: Cross sectional area

6 Brake Fluid

Brake fluid refers to the liquid that fills the caliper, master cylinder, and brake lines at all times. As the master cylinder is compressed, the brake fluid is pressurized and exacts a pressure inside the caliper, causing the pistons to contract. 

Important Variables: Viscosity, volume, pressure, etc

7 Master Cylinder

The master cylinder can be simplified to be a piston. Essentially, when the plunger is pushed, the pressure in the cylinder increases, and thus the tubes and the caliper pressure increases. The diameter of the plunger and the amount of depression directly affect the braking force.

Important Variables: Diameter

8 Pedal

The pedal is simply a swing arm that is almost directly connected to the master cylinder designed to allow for a foot to apply pressure (with appropriate feedback caused by the opposing forces occurring in the master cylinder). 

Important Variables: Travel distance ratio (pedal travel to cylinder travel)

Component Selection & Justification

Master Cylinder: Remote Tandem Master Cylinder w/ Pushrod

 ( https://www.wilwood.com/MasterCylinders/MasterCylinderProd?itemno=260-14241-BK )

• able to mount reservoir separately to cylinder for ease access etc
• able to add on proportioning valve if we need one
• has tandem outputs (2 outputs) one for rear and front
• has varying bore sizes from ⅞ to 1-⅛”

Pedal Assembly Design: Team elected to custom design pedal and mounting system. Components that need to be designed are as follows:

• Pedal Face Plate: pressing face used to adjust the pedal. Should be designed in parallel with lever
• Lever: swing arm used to grant enough leverage to compress the master cylinder. Geometry should be adjusted based on connection point, and master cylinder compression
• Lever hinge: clevis/hinged mount where the lever will attach to the mounting plate.
• Mounting plate: similarly to MSVII, a plate will be required to mount the pedal, master cylinder, etc to the chassis. 
• Remote reservoir mounting solution: Team has elected to select a remote master cylinder, where the reservoir will be remotely connected to the master cylinder. The reservoir will need to be mounted somewhere (preferably with an adjustable mount that can be relocated as necessary).
• Master cylinder connection: Some type of design solution needs to be created to allow for the master cylinder to be connected with the lever. This job will be heavily related to lever design, however, has it's own complexities. It should allow for some adjustment as required, however, should not allow for any play once installed (last pedal allowed for significant amount of unexpected movement due to poor connection)

Team members will be assigned on designing one (or two) components, and ideally will work collaboratively to create the entire brake pedal system.

Callipers and Brake Pads: To be decided on once mathematical model can be completed.