A pivoting lever forming part of the electromagnetic brake assembly on a traction machine, applying clamping force from the brake spring to the brake drum or disc surface when the coil is de-energised.
Full Definition
The brake arm is a precision-machined steel lever that transmits spring force to the brake lining, creating the friction torque that holds the elevator at rest. In a dual-arm (symmetric) brake, two arms clamp the drum from opposite sides, ensuring balanced radial loading. The arm pivot is a hardened steel pin with either a plain or rolling-element bearing. Arm geometry determines the mechanical advantage between spring force and brake pad pressure; this geometry must be maintained within manufacturer tolerances to achieve the specified brake torque. Adjustment of air gap (typically 0.3–0.5 mm between lining and drum when brake is open) is performed at commissioning and during maintenance. EN 81-20 requires the brake to be capable of stopping and holding the car with 125% of rated load. Wear of the arm pivot bearing causes brake release asymmetry and must be corrected promptly.
