Brake Systems Theory
The basic function of the brake system in a vehicle is to convert Kinetic Energy into Heat Energy. This is done by the brake system converting momentum of the vehicle into heat energy at the brakes through the moving brake rotor/drum and a frictional material, better known as brake pads/shoes.
It should be known that energy cannot be destroyed; only converted. Thus once we convert the momentum of a vehicle or Kinetic Energy into Heat Energy through brake application or friction, a vehicle will come to a stop and is held in place by Static Friction. Static Friction can also be referred to as Pressure and the road we drive is a form of Static Friction.
There are four factors that determine the effectiveness of the braking system. The first three are factors of friction (Pressure, Coefficient of Friction (COF) and Frictional Contact Surface). The forth is a result of the first three which is created as a result, Heat or Heat Dissipation.
-Pressure, the greater the pressure that is applied by the braking system the more heat friction which will develop at the brake units. This is achieved by brake pedal force though hydraulic pressure multiplication of the master cylinder to the braking system via the brake lines and fluid.
-Coefficient of Friction (COF) is the amount of friction generated between two surfaces, or the relationship between the frictional brake pads/shoes and the brake rotors/drums. COF can be expressed as a mathematical equation that is used to determine frictional material’s effectiveness to stop a vehicle. COF is determined by dividing the force required to pull an object across a surface by the weight of the object. So if you have a 100 pound object and it requires 100 pounds of force to pull that object, the equation would be 100 divided by 100 for a COF of 1.
-Frictional Contact Surface is the amount of surface area in contact with the frictional brake material while braking. Simply stated, that the larger a vehicles brakes are the easier it is to stop then smaller brakes.
-Heat Dissipation is the biggest factory in the effectiveness in a vehicles ability to stop safely. A brake system must be designed properly to conduct the heat away from the pads/shoes and rotors/drums and be absorbed into the surrounding air. The inability to properly dissipate heat will result in Brake Fade and loss of braking power with longer stopping distances.
Brake Fade is commonly caused by excessive heat build up during braking. The brake pedal will feel normal, but the ability to stop is drastically reduced. During braking and as heat is generated from the friction, the pad/shoe linings generate a gas. This result is called out-gassing or off-gassing. This gas can quickly form an air gap between the frictional material and the braking surface. As brake pressure is applied, the clamping force will slip on the gas, and this in known as brake fade.
It should also be known, that Brake Fade can also be caused if, brake fluid (which is hygroscopic) absorbs too much moisture and its boiling point is lowered, causing a gas in the fluid from excessive heat build up. Fluid is not compressible, but gas in the fluid can easily be compressed.
Brake Systems Theory
The basic function of the brake system in a vehicle is to convert Kinetic Energy into Heat Energy. This is done by the brake system converting momentum of the vehicle into heat energy at the brakes through the moving brake rotor/drum and a frictional material, better known as brake pads/shoes.
It should be known that energy cannot be destroyed; only converted. Thus once we convert the momentum of a vehicle or Kinetic Energy into Heat Energy through brake application or friction, a vehicle will come to a stop and is held in place by Static Friction. Static Friction can also be referred to as Pressure and the road we drive is a form of Static Friction.
There are four factors that determine the effectiveness of the braking system. The first three are factors of friction (Pressure, Coefficient of Friction (COF) and Frictional Contact Surface). The forth is a result of the first three which is created as a result, Heat or Heat Dissipation.
-Pressure, the greater the pressure that is applied by the braking system the more heat friction which will develop at the brake units. This is achieved by brake pedal force though hydraulic pressure multiplication of the master cylinder to the braking system via the brake lines and fluid.
-Coefficient of Friction (COF) is the amount of friction generated between two surfaces, or the relationship between the frictional brake pads/shoes and the brake rotors/drums. COF can be expressed as a mathematical equation that is used to determine frictional material’s effectiveness to stop a vehicle. COF is determined by dividing the force required to pull an object across a surface by the weight of the object. So if you have a 100 pound object and it requires 100 pounds of force to pull that object, the equation would be 100 divided by 100 for a COF of 1.
-Frictional Contact Surface is the amount of surface area in contact with the frictional brake material while braking. Simply stated, that the larger a vehicles brakes are the easier it is to stop then smaller brakes.
-Heat Dissipation is the biggest factory in the effectiveness in a vehicles ability to stop safely. A brake system must be designed properly to conduct the heat away from the pads/shoes and rotors/drums and be absorbed into the surrounding air. The inability to properly dissipate heat will result in Brake Fade and loss of braking power with longer stopping distances.
Brake Fade is commonly caused by excessive heat build up during braking. The brake pedal will feel normal, but the ability to stop is drastically reduced. During braking and as heat is generated from the friction, the pad/shoe linings generate a gas. This result is called out-gassing or off-gassing. This gas can quickly form an air gap between the frictional material and the braking surface. As brake pressure is applied, the clamping force will slip on the gas, and this in known as brake fade.
It should also be known, that Brake Fade can also be caused if, brake fluid (which is hygroscopic) absorbs too much moisture and its boiling point is lowered, causing a gas in the fluid from excessive heat build up. Fluid is not compressible, but gas in the fluid can easily be compressed.
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