Hydraulic Brake and Clutch Assemblies Information

Hydraulic clutch and brake assemblyPower transmission systems delivering rotational energy from a power source to working equipment are found throughout industry and transportation. Hydraulic brake and clutch assemblies play an import role when space utilization is important. Hydraulic brake and clutch assemblies consist of a hydraulic clutch for engaging power from the power source to the rotating assembly and a hydraulic brake used to slow or stop rotating equipment. Hydraulic brake and clutch assemblies are distinguished from mechanical brake and clutch assemblies in the way the braking and clutching components are actuated. Most hydraulic brakes and clutches use an incompressible fluid such as oil to engage/disengage and to also slow drivelines. Some hydraulic brakes are regenerative and convert kinetic rotating energy to electricity. Engaging the clutch transfers power from an engine or motor to driven devices such as a transmission or drive sprockets for a conveyor. Disengaging the clutch stops the power transfer, but allows the motor to continue turning. Braking slows or stops the movement of coupled shafts. Because they are self-regulating, hydraulic brake and clutch assemblies require less maintenance than many mechanical systems.


Hydraulic brake and clutch assemblies are used in production equipment such as packaging, processing, web equipment, and warehousing. They can also be found in transportation and off road vehicles; they are normally used in automobiles. Any application requiring regular disengaging and engaging gears, pulleys, belts, chains, and other rotating devices are good candidates for a hydraulic brake and clutch assembly.


When specifying  hydraulic brake and clutch assemblies, certain application specific variables are important to keep in mind. When selecting hydraulic brake/clutch properties, consider:

  • Torque Rating
  • Power
  • Rotational Speed
  • Maximum Hydraulic Pressure
  • Mounting Geometry—Inline, Parallel, Right Angle
  • Connection Interface


Clutch engagement is the major differentiator between clutch types:

  • Noncontact—Use a noncontact technology such as a magnetic field or eddy currents to provide engagement and drive. 
  • Friction—Between contact surfaces transmits power. This is the most common configuration. 
  • Toothed—Toothed contact surfaces transmit power without slipping. No heat is generated. Devices are engaged only when stopped or running at a slow speed (< 20 rpm). 
  • Wrap Spring—Torque is transmitted from input to output by a coiled spring that wraps around the output element. The device is disengaged when the spring is uncoiled via a control tang at its end. 
  • Oil ShearDrive engagement is achieved by the viscous shear of transmission fluid between the device's plates. 
  • Plate/Disc—The torque level is controlled by compression springs that force plates together. 
  • Ball Detent—Ball detent is a slip mechanism in which, upon overload, balls ride up out of seats to overcome springs or air pressure engagement. 
  • Roller Detent—Rollers, held in place by springs, wedge between the inner and outer races to engage the clutch. 
  • Pawl Detent—Pawl detent is a slip clutch mechanism in which, upon overload, the pawl overcomes spring or air pressure engagement and rotates out of its detent. 

Brakes operate using a broad range of methods. Different types of operations available include:

  • Noncontact—Braking action is achieved through a non-contact technology such as a magnetic field, eddy currents, etc. 
  • Friction—Friction between contact surfaces transmits power. This is the most common type of brake. 
  • Toothed—Toothed contact surfaces transmit power without slipping or heat generation. Teeth are engaged only when stopped or running at a slow speed (< 20 rpm). 
  • Wrap Spring—A coiled spring wraps downward onto the rotating element. The brake is disengaged when the spring is uncoiled via a control tang at its end. 
  • Oil Shear—Braking action is engaged via the viscous action of the shearing of transmission fluid.

Brakes have several construction styles to achieve adequate braking force:

  • Band—Band brakes are the simplest type of brake. They have a metal band lined with heat- and wear-resistant friction material. 
  • Drum—Drum brakes press shoes against a spinning surface. They are often used on automobile rear wheels. 
  • Disc—Disc brakes have brake pads, a caliper, and a rotor. During operation, the brake pads are squeezed against the rotor. Disc brakes have good heat dissipation properties. 
  • Cone—Cone brakes consist of a cup and a cone that is lined with a heat- and wear-resistant friction material. During actuation, the cone is pressed against the mating cup surface. Cone brakes are not commonly used. 

Hydraulic brakes and clutches are popular among industrial and mobile systems to both impart rotational energy to a rotating device using a clutch and to remove kinetic energy from a rotating system using a brake. While nearly all rotating systems will require a clutch to disconnect and connect the power source and a brake to slow or stop the system, clutch/brake assemblies allow for robust design without sacrificing space.

Related Information

CR4 Community—Recycle Your Brakes?

Image credit:

J.C. Fields / CC BY-SA 3.0