Brake System Design and Optimization: Brake System Purpose and Layout
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Brake System Purpose and Layout
06.22
| 00:00 | - Before we get too deep looking at each component of the braking system in more detail, it's important that we first understand the purpose and underlying concepts that the braking system relies on. |
| 00:12 | So that's what we'll be doing in this set of modules, building a strong foundation of the fundamentals before getting into the finer details of each component. |
| 00:20 | The purpose of the braking system is simply to slow the car down. |
| 00:24 | In a motorsport context, we generally want to do this in as short a distance and time as possible. |
| 00:31 | It's worth mentioning here that there are a few different contributing factors that slow the car down besides the braking system. |
| 00:38 | The main ones being aerodynamic drag, friction within the vehicle's drive line and tyre drag. |
| 00:44 | While each of these components can be significant in their own right, in almost all practical cases, the braking system provides much more retarding force than all of these other effects combined. |
| 00:56 | When considering the basic principles of what's happening when we're braking, it's helpful to think of the whole vehicle system from an energy perspective. |
| 01:04 | What I mean by this is when a vehicle is travelling at a constant speed, it has a certain amount of energy. |
| 01:11 | This is in the form of kinetic energy. |
| 01:13 | The energy associated with an object of a given mass travelling at a given velocity. |
| 01:19 | When we use a conventional friction based braking system to slow a car down, we're essentially converting that kinetic energy into thermal energy. |
| 01:27 | The amount of kinetic energy the vehicle has is reducing and as a result the brakes get hot. |
| 01:34 | The source of the friction that makes this energy exchange possible in modern brakes, comes from a consumable material being pressed against a solid rotating surface. |
| 01:43 | In all modern braking systems, this will be in the form of brake pads being squeezed against a brake disc. |
| 01:50 | It's worth also noting here that the disc itself will also be considered a consumable, it just wears at a much slower rate than the pad. |
| 01:58 | Because this friction force is applied at a distance from the centre of rotation of the brake disc, this leads to a torque that acts to slow down the speed the brake disc is turning at. |
| 02:08 | The brake disc is mechanically connected to the wheel and tyre assembly and therefore the tyres exert a force on the road surface, slowing the car down. |
| 02:18 | In the interest of completeness, there's another type of braking system known as a drum brake that can be found on many older cars. |
| 02:27 | This is where a set of brake shoes are pushed out radially onto an inner surface of a drum. |
| 02:33 | While this style of brake used to be common, you'll struggle to find it on any modern road car and certainly not anything high performance. |
| 02:40 | The exception to this is some modern cars do use a drum type brake for a parking brake exclusively while using a disc for the main braking. |
| 02:50 | The reason for this is one big advantage drum brakes have over discs is they can be more effective when used statically in order to prevent a stationary car rolling. |
| 03:00 | Drum brakes are inferior in almost every other aspect when compared to disc brakes and for this reason, we'll be ignoring them from here on out. |
| 03:09 | The general layout and working principles for modern disc brakes are largely identical for most applications. |
| 03:16 | Here in this section of the course we'll go through each component starting at a high level before discussing them in more detail later in the course. |
| 03:24 | The system begins with a brake pedal. |
| 03:27 | The force applied to the brake pedal by the driver is the primary means of controlling the brake force. |
| 03:33 | The brake pedal will have a mechanical linkage that applies force to a hydraulic master cylinder. |
| 03:39 | In road cars there is generally a device called a brake booster, otherwise known as a brake servo, between the brake pedal and master cylinder. |
| 03:48 | The purpose of a brake booster is to reduce the amount of force required by the driver to actuate the brakes. |
| 03:55 | In motorsport applications, we often don't use a brake booster but we'll discuss this in more detail later in the course. |
| 04:03 | It's also worth nothing that in some modern applications, there is no physical connection between the brake pedal and the master cylinder. |
| 04:10 | This is what's referred to as brake by wire. |
| 04:14 | This simply means that the brake pedal is connected to a sensor that monitors how much force is applied. |
| 04:19 | An electric control unit then decides based on the current status of the vehicle, how much braking force should be applied to the master cylinder which it'll do via an actuator. |
| 04:30 | Brake by wire systems are particularly common in hybrid applications to help the vehicle manage regenerative braking strategies. |
| 04:39 | In this course, we won't be discussing brake by wire or the application of regenerative braking, only conventional, direct acting brakes found in the vast majority of both road and racecar applications. |
| 04:53 | With a force applied to the master cylinder, hydraulic pressure is built up inside its main chamber. |
| 04:59 | This hydraulic pressure is transferred to the brake caliper via a brake line. |
| 05:04 | These are often made up of both solid and flexible sections. |
| 05:08 | flexibility is required in some parts as the brake calipers will generally move with the suspension. |
| 05:13 | With the hydraulic pressure now transferred to the brake calipers, the piston inside the calipers are forced out of the caliper body. |
| 05:21 | These pistons press against the brake pads, one side of which has a sacrificial friction material applied to it and this is the side that's squeezed against the rotating brake discs. |
| 05:32 | The friction material is designed to be consumed over time as each application of the brakes eats away at the pad's surface. |
| 05:41 | Again, the disc will also be worn down but at a lesser rate. |
| 05:45 | The resulting friction between the pads and the disc results in a brake force that retards the car and slows it down. |
| 05:52 | To summarise what we've covered in this module, the braking system of the car is the primary means of slowing it down. |
| 05:59 | It does this by converting kinetic energy that the car has when moving, primary into thermal energy. |
| 06:06 | The braking system takes a mechanical force input by the driver, transfers this force using hydraulics to the brake caliper, which then applies a braking torque to the disc to slow the car down. |
