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Curved Brake Disc Vanes on Armored Vehicles
Ventilated discs are used on many vehicles. The air gap gives an increase in surface area that helps the disc to cool down more quickly through convection. The disc friction plates are joined by vanes which are usually straight or curved.
High-performance brake discs often have curved cooling vanes. These generally hand the discs where they run back from the inside to outside diameters in the direction that the disc is rotating (as seen in the image, right). They are important for helping cool brake discs that are rotating fast on high-speed vehicles by aiding cool airflow through the air gap in the disc.
Curved vanes are not necessary for additional cooling on “normal” speed vehicles but are often used to increase the structural integrity of the disc, giving additional strength.
When braking, heat causes the disc friction plate(s) to expand. This is restricted by the cooler bell. This may cause a crack to form. If this starts at the outside diameter of the disc, then it can run radially toward the disc inside diameter, effectively splitting the disc open. Curved vanes disrupt this crack path where straight vanes would allow it more freely.
Most higher-production discs are manufactured using non-handed castings. Where curved vanes are used, they may appear to go in the wrong direction on one side of the vehicle. The brake engineers specifying this understand the temperature that the disc will see and the cooling available in order to make this decision.
A common example of this practice, at Alcon, is on armored vehicles. Temperatures generated from stopping a heavy vehicle can cause higher-than-normal thermal expansion, but the speeds seen on the vehicle are not fast enough to require handed curved vanes.
Technical article provided by Alcon Components Ltd. Published by AlconKits with permission.