Different shoe-type brakes

There are various patterns of internal-expanding shoe-type brakes.

There are two patterns of the Simplex brake embodying mechanical arrangements whereby better braking power is obtained by so-called self-servo action.

Another example of the internal-expanding brake is the Duplex brake: in this arrangement each shoe has its own wheel cylinder which acts in one direction only, pressing one shoe against the drum, while the other shoe serves as a support for thrusting against.

In this system the shoes are so mounted that, when the vehicle is travelling in the forward direction, the drum tends to carry each shoe around with it in the direction away from the pivot point of the shoe. This makes for efficient braking by self-servo action.

On the other hand, the braking action is rather poor when the vehicle is reversing.

Besides the single-circuit brake systems described here, dual-circuit hydraulic systems comprising a tandem master cylinder which contains two pistons that are actuated by the brake pedal. The front piston transmits its force to the rear one, so that hydraulic pressure is developed in two circuits.

The advantage of the two-circuit braking system is that if an oil pipe in one circuit fractures, the second circuit will still continue to function.