Question

Disk brakes often have the clamping mechanism at the edge of the device. Explain why this is and back up your logic with an equation.

Answer 1

Solution

This is due to the fact that the applied retardation to the device will be higher if brake system is clamped at the edge.

The tourque applied by a force is given by,

Where F is the magnitude of applied force and R is the perpendicular distance from axis of rotation to the force. In the case of a tyre, R will be the radial distance from axis of tyre to the braking system where it is clamped. If it is clamped at the far edge of disk, the applied torque( which stops the tyre) will be higher compared to a brake which can provide same frictional force F but clamped at a smaller distance from axis. So we can effectively utilize maximum stopping effect from the brakes by clamping it at the far edge of the disk.

This is the same principle by which you can open a gate by pushing it at the edge rather than at some inner points. Torque effects are considered where ever rotational motion comes into play.