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Resources | Product Training | PT/MC Tech Tips | Clutches & Brakes

Tech Tip: Clutches & Brakes

Enhance your employees’ product and industry knowledge with PTDA’s Tech Tips. This library of online tips, hints and techniques may be used to educate new and current employees on power transmission/motion control (PT/MC) products, technologies and concepts and serve as reference and reminder for more experienced staff. Tech Tips are based on the expertise of PTDA member companies, content from Motion Control Made Simple or PTDA’s Power Transmission Handbook®, the definitive resource and training tool on PT/MC products.

Visit the full library of Tech Tips for additional products.

What three clutch techniques are commonly used in backstop applications and why?

Sprag, wrap-spring, and ramp and roller style clutches are used in backstop applications due to their self-actuated technology that does not require any input signal to engage when reverse rotation occurs. These all provide low to zero backlash backstopping.

Why use a mechanical lock-up style clutch over other technologies?

The design of mechanical lock-up clutches allow for their use in applications that require no-slip engagement and cycling that other clutch technologies cannot meet. They also can be used in backstopping, overrunning and indexing applications that other clutch technologies cannot.

Why do I hear noise in the newly installed friction clutch/brake?  

It is not uncommon in a newly installed friction clutch/brake for there to be a chirp or brief squeal as the unit engages; as the unit burnishes this will normally go away. Never add any lubricant to try to eliminate this noise as it will disrupt the function of the unit.

Cause of Rapid Unit Failure in a Wrap Spring Clutch/Brake

The rectangular plate commonly used in wrap spring clutch/brakes should be considered a torque arm.  Therefore it should be mounted so that there is some play or compliance in the mounting.  Rigidly mounting the plate will result in binding and rapid unit failure.

Lubrication of Overrunning Clutches

When lubricating an overrunning clutch or backstop, there will be multiple possible recommended lubrication choices from the manufacturer.  It is critical that lubrication of an overrunning clutch or backstop not include extreme pressure (EP) additives.  Overrunning clutches use the gripping force of the sprags and the clutch races to transmit torque.  EP additives will disrupt this gripping force.

Use of New Electro-Magnetic Friction Clutches or Brakes

Many electro-magnetic friction designs require a wear-in or burnishing process to achieve full torque upon new installation (or after rebuilding).  This process can commonly take from 50-100 on-off cycles.  Generally, a burnishing process will call for one-second-on and one-second-off cycling.  Manufacturers are able to hold friction surface flatness within a few thousandths of an inch.  Burnishing will wear down any high spots and allow for full friction face engagement.

Noise in Friction Clutches/Brakes

It is not uncommon in newly installed friction clutch/brakes for there to be a chirp or brief squeal as the unit engages; as the unit burnishes, this will normally go away.  Never add any lubricant to try to eliminate this noise as it will disrupt the function of the unit.

The information provided in Tech Tips is not meant to be all-encompassing, but rather to draw attention to and provide information about the particular subjects covered. All suggestions and recommendations contained in Tech Tips are based upon information that is believed to be accurate to the best of the experience and knowledge of PTDA’s contributing members, but are made without guarantee or representation as to results. PTDA and Tech Tip contributors expressly disclaim any warranties or guaranties, express or implied, as to the accuracy or completeness of any information published in Tech Tips, and disclaims and makes no warranty that the information in Tech Tips will fulfill any of your particular purposes or needs. PTDA and Tech Tip contributors disclaim liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on Tech Tips.