Effect of Thermo-Mechanical Behavior on Drum Brake Labyrinth Design

In low speed bikes drum brakes are used on large scale. In drum brake system, brake shoes are relatively more enclosed by neighboring parts compared to disc brakes. Hence, drum brake cooling is not efficient like disc brake. This results in higher steady state temperature, which may lead to brake noise, brake fading, glazing etc. in drum brakes. Further, the high temperature plays a key role for design of labyrinths too. Hence, designing of the drum brakes for extreme heating is critical. This paper elucidates the thermo-mechanical behavior in two-wheeler drum brakes under extreme braking and their consequence manifesting itself in permanent distortions resulting in the brake failure. Experiments as well numerical simulations are carried out to investigate the thermo-mechanical behavior of drum brakes. Experiments are conducted at extreme braking for maximum thermal loading on the drum brake. The rise in temperature of the drum is measured with sensor. The generated heat energy causes brake drum to expand both in lateral and radial directions. Under extreme braking condition rubbing of brake drum with brake panel is observed in the case of low clearance between drum and panel. Hence it is important to design the drum braking system taking extreme thermal loading into consideration. At design stage it is essential to predict the proper clearances and dimensions of the drum brake for better thermal performance and safety. Numerical simulations are conducted to predict the thermal behavior of drum brakes under severe braking condition. Finite element analysis has been performed with commercially available software. Thermal expansion comparisons are made between spoke wheels and alloy wheels. The simulation method is useful for design validation of the drum brake system upfront of the product development.