Difference between revisions of "Brake Rotors"
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<span>Brake rotors, or just rotors, are the discs that rotate with the wheel and provide a surface for the brake pads to apply friction to. They can be made using a wide variety of materials and manufacturing methods depending on the system they are used in, mostly dependent on the brake pad material.</span> | <span>Brake rotors, or just rotors, are the discs that rotate with the wheel and provide a surface for the brake pads to apply friction to. They can be made using a wide variety of materials and manufacturing methods depending on the system they are used in, mostly dependent on the brake pad material.</span> | ||
| − | == | + | ==Materials== |
<span>The selection of material is highly dependent on the engineer's design goals for rotor operating temperature, pad-rotor coefficient of friction, material strength and other properties.</span>Rotors can be constructed using the following materials: | <span>The selection of material is highly dependent on the engineer's design goals for rotor operating temperature, pad-rotor coefficient of friction, material strength and other properties.</span>Rotors can be constructed using the following materials: | ||
| − | * Steels of low to high carbon% | + | * Steels of low to high carbon% |
* Chromoly (4130 Steel) or other alloys | * Chromoly (4130 Steel) or other alloys | ||
* Cast Iron | * Cast Iron | ||
| Line 11: | Line 11: | ||
Typically pad-rotor coefficients of friction and ideal pairings will be specified by the brake pad manufacturer, but this can also be physically tested and verified in-house by teams who have the resources to do so. | Typically pad-rotor coefficients of friction and ideal pairings will be specified by the brake pad manufacturer, but this can also be physically tested and verified in-house by teams who have the resources to do so. | ||
| − | == | + | ==Lightening== |
| − | + | [[File:Fig.-3.png|right|middle|thumb| Rotor dimple pattern on UA-21 rotor design, dotted lines represent dimples on opposite side of rotor.]] | |
| − | A common practice is the drilling of holes or slots into or all the way through the rotor. This practice has several effects on brake performance: | + | A common practice is the drilling of holes or slots into or all the way through the rotor. This practice has several effects on brake performance: |
* Decreasing the area of contact between the pad and rotor, thus impeding the flow of heat into the rotor but also venting heat off the pad | * Decreasing the area of contact between the pad and rotor, thus impeding the flow of heat into the rotor but also venting heat off the pad | ||
* Adds a shaving effect to keep the pad surface clean | * Adds a shaving effect to keep the pad surface clean | ||
* Increases rotor temperatures through reduction of thermal mass | * Increases rotor temperatures through reduction of thermal mass | ||
* Decreases rotational inertia of system | * Decreases rotational inertia of system | ||
| − | |||
| − | |||
| + | ==Venting== | ||
Vented rotors are rotors with fins in between either contact surface that allow air to pass inside the rotor itself. The way air travels through the rotor is dependent on the configuration of the fins inside. | Vented rotors are rotors with fins in between either contact surface that allow air to pass inside the rotor itself. The way air travels through the rotor is dependent on the configuration of the fins inside. | ||
A common misconception among designers is that doing this increases cooling effects on the brake rotor by increasing it's surface area. While drilling holes in the rotor does increase surface area, unless there is some form of air actively being guided through those holes either by brake/wheel ducts or winglets, there is no significant airflow through the holes of the rotor. Conversely, vented brake discs which are common in larger vehicles, have improved cooling as the vane design is orthogonal to the axis of rotation, not parallel, and is significantly influenced by airflow within the wheel. A study by Arthur Stephens at RMIT showed that cooling of a disc brake was improved by using an alloy wheel with a large open area.In heating tests (during braking), the initial rate of heating is a function of the thermal storage capacity of the rotor, and it was found that the thermal performance of a solid and an equivalent-sized vented rotor was similar.<ref>Stephens, Arthur (2010). Aerodynamic cooling of automotive disc brakes. RMIT University. Thesis. https://doi.org/10.25439/rmt.27580428</ref> In cooling, the vented rotor cooled faster than the solid rotor. Students seeking to improve cooling of the rotor should evaluate their designs using similar methods to the linked paper and consider airflow into the wheel well. | A common misconception among designers is that doing this increases cooling effects on the brake rotor by increasing it's surface area. While drilling holes in the rotor does increase surface area, unless there is some form of air actively being guided through those holes either by brake/wheel ducts or winglets, there is no significant airflow through the holes of the rotor. Conversely, vented brake discs which are common in larger vehicles, have improved cooling as the vane design is orthogonal to the axis of rotation, not parallel, and is significantly influenced by airflow within the wheel. A study by Arthur Stephens at RMIT showed that cooling of a disc brake was improved by using an alloy wheel with a large open area.In heating tests (during braking), the initial rate of heating is a function of the thermal storage capacity of the rotor, and it was found that the thermal performance of a solid and an equivalent-sized vented rotor was similar.<ref>Stephens, Arthur (2010). Aerodynamic cooling of automotive disc brakes. RMIT University. Thesis. https://doi.org/10.25439/rmt.27580428</ref> In cooling, the vented rotor cooled faster than the solid rotor. Students seeking to improve cooling of the rotor should evaluate their designs using similar methods to the linked paper and consider airflow into the wheel well. | ||
| + | |||
| + | Analysis and simulation of rotors in a Formula SAE vehicle was described in Matthew Heffernan's paper at Auburn University.<ref>Heffernan, M., "Analyzing and Simulating Brake Rotor Temperatures: A Technique Applied to a Formula SAE Vehicle," SAE Technical Paper 2006-01-1974, 2006, https://doi.org/10.4271/2006-01-1974</ref> | ||
<references /> | <references /> | ||
Latest revision as of 10:52, 6 May 2026
Brake rotors, or just rotors, are the discs that rotate with the wheel and provide a surface for the brake pads to apply friction to. They can be made using a wide variety of materials and manufacturing methods depending on the system they are used in, mostly dependent on the brake pad material.
Materials
The selection of material is highly dependent on the engineer's design goals for rotor operating temperature, pad-rotor coefficient of friction, material strength and other properties.Rotors can be constructed using the following materials:
- Steels of low to high carbon%
- Chromoly (4130 Steel) or other alloys
- Cast Iron
- Aluminum Alloys
- Carbon ceramic
Typically pad-rotor coefficients of friction and ideal pairings will be specified by the brake pad manufacturer, but this can also be physically tested and verified in-house by teams who have the resources to do so.
Lightening
A common practice is the drilling of holes or slots into or all the way through the rotor. This practice has several effects on brake performance:
- Decreasing the area of contact between the pad and rotor, thus impeding the flow of heat into the rotor but also venting heat off the pad
- Adds a shaving effect to keep the pad surface clean
- Increases rotor temperatures through reduction of thermal mass
- Decreases rotational inertia of system
Venting
Vented rotors are rotors with fins in between either contact surface that allow air to pass inside the rotor itself. The way air travels through the rotor is dependent on the configuration of the fins inside.
A common misconception among designers is that doing this increases cooling effects on the brake rotor by increasing it's surface area. While drilling holes in the rotor does increase surface area, unless there is some form of air actively being guided through those holes either by brake/wheel ducts or winglets, there is no significant airflow through the holes of the rotor. Conversely, vented brake discs which are common in larger vehicles, have improved cooling as the vane design is orthogonal to the axis of rotation, not parallel, and is significantly influenced by airflow within the wheel. A study by Arthur Stephens at RMIT showed that cooling of a disc brake was improved by using an alloy wheel with a large open area.In heating tests (during braking), the initial rate of heating is a function of the thermal storage capacity of the rotor, and it was found that the thermal performance of a solid and an equivalent-sized vented rotor was similar.[1] In cooling, the vented rotor cooled faster than the solid rotor. Students seeking to improve cooling of the rotor should evaluate their designs using similar methods to the linked paper and consider airflow into the wheel well.
Analysis and simulation of rotors in a Formula SAE vehicle was described in Matthew Heffernan's paper at Auburn University.[2]
- ↑ Stephens, Arthur (2010). Aerodynamic cooling of automotive disc brakes. RMIT University. Thesis. https://doi.org/10.25439/rmt.27580428
- ↑ Heffernan, M., "Analyzing and Simulating Brake Rotor Temperatures: A Technique Applied to a Formula SAE Vehicle," SAE Technical Paper 2006-01-1974, 2006, https://doi.org/10.4271/2006-01-1974
