Commercial Shearing is a major supplier of hydraulic equipment and solutions and specialises in custom manufacture, and the supply and service of pumps, motors, valves, gear pumps, hydraulic filters and much more, all covered in its extensive catalogue. The company recently completed an order where the brief was to design and manufacture a hydraulic test stand for spring applied hydraulic brakes with hydraulic release on vehicles.
The operation of the brakes is as follows: in park (Failsafe) the brake is applied by springs acting on friction plates. When the vehicle is driven, the brake is released by applying pressure to an internal cylinder. This compresses the springs and releases the force applied to the friction plates, allowing the vehicle to drive. To allow the vehicle to slow down or stop (Service), an opposing pressure is applied to the opposite side of the cylinder. This compresses the friction plates and the vehicle slows or comes to a stop.
Brake test specifications
A maximum static torque of 2 kN/m is applied to the brake in Failsafe mode and the brake must hold. A maximum torque of 3 kN/m is applied to the brake in Service mode when the brake is applied. The torque simulation is applied to the brake by stalling a 800 cc/rev hydraulic motor. The brake is released (Failsafe mode) by applying pressure through an adjustable pressure reducing valve, which allows the motor to run. The brake is applied (Service mode) by applying pressure through an adjustable pressure reducing valve and this stalls the hydraulic motor. Torque figures are recorded via pressure gauges.