A mechanical braking arrangement where two brake shoes press against the front and back of a single wheel tread simultaneously. This design prevents the axle from being pushed out of alignment during heavy braking, distributing the stopping force and reducing thermal stress on the wheel compared to single-shoe setups.
The car knocker found a missing pin on the clasp brake rigging of the third axle.
While newer freight cars often use single-shoe brakes to save weight, heavy locomotives and older passenger equipment still rely on the double-shoe clasp design for maximum stopping power.
Related terms
Brake pipe
The air line running the full length of a train that charges and controls every car's brakes.
Car knocker
A carman, the mechanical worker who inspects and repairs railcars and tests their brakes.
Triple valve
The core control valve in a railway air brake system that charges, applies, and releases the brakes.