How Mechanical disc brake work?

complicated said:

hi..
do anyone know how mechanical disc brake work? what happened inside the caliper?

one pad stays staionary while the other presses the rotor against it when the cable is pulled.

is that what you are asking?

Yes, but what happened inside the caliper? Is there cam or what in it?

It depends on the caliper, but usually they are a variation of ball-and-ramp.
The Formula Activas I had were about the simplest of the caliper designs, so I will use them as an example.

The pad is mounted on a rotating spindle that has a shaft extending through the caliper body out to the actuating lever. Inside the caliper, between the housing and the flange of the spindle are 4 ball bearings that ride on corresponding ramps. When the actuating lever is turned, it turns the spindle which, by motion of the ramps, forces the pad to clamp the rotor.

A clever design, really. Hydraulics still rock. 🙂 Shimano 525 Hydro