Carbon Brush Springs: Constant Force to Optimize Wear Rate

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Carbon Brush Springs: What Our Research Says About Constant Force and Wear Rate

Many times, carbon brush holders that claim to use constant force springs are actually not constant force at all.  A proper holder allows full spring force throughout a carbon brush’s life.  Most holders are poorly designed and fail to be “constant force” for two main reasons:

  1. The spring diameter is too large
  2. Inferior backplate design
    • The spring starts too high in the brush box.
    • The spring does not sit properly on the top of the brush.

How Constant Force Springs Can Improve Carbon Brush Wear Rate

For a spring to be a true constant force, the spring must be uncoiled one full diameter to be at the rated force, and when recoiled to less than one diameter, the force begins to drop off.

Typically, during sliding electrical contact applications, a carbon brush will experience both mechanical and electrical wear.  Spring force plays a significant role in determining carbon brush wear rates. While higher spring forces tend to increase mechanical wear, lower spring forces can lead to increased electrical wear. Therefore, finding the optimal spring force balance is crucial for minimizing overall brush wear.


Helwig Carbon constant force spring differences to OEM


Helwig Carbon constant force spring differences to OEM


Maximize Brush Life with Helwig’s Replacement Spring Assemblies  

A handful of OEMs use brush holders with large diameter springs that do not offer constant force throughout the carbon brushes’ life.  In fact, on some designs, the spring force drops off rapidly, causing increased brush wear and sometimes even damage to the commutator surface from intensified arcing.Upgrade your brush performance with Helwig Carbon’s engineered carbon brush spring solutions. Replace poorly designed holders with reliable, high-quality parts.  

Engineered to Attain True Constant Force 

  • Smaller Diameter Springs: Helwig Carbon has engineered replacement carbon brush spring assemblies that use a smaller diameter spring to prevent unnecessary wear from occurring. resulting in an increased length of consistent force throughout the brushes’ life.
  • Backplates: We have also redesigned the backplates to allow the springs to sit closer to the center of the carbon brush, thus distributing the spring force evenly across the two brush wafers. Our precisely engineered springs create longer brush life and less likelihood of damage to the commutator surface with increased motor performance.

Brush Wear Indicators: This is the industry’s most convenient way to monitor brush wear. Using the red ”danger strip,” our Brush Wear Indicators inform you the brush should be replaced. The other spring upgrade option is Helwig Quick Disconnects (HQDs), which lock together with a tight, positive locking action even under rough conditions, with no screws to remove, lose or replace!

For more information regarding our pioneering research on spring pressure, please download our whitepaper: The Effect of Spring Pressure on Carbon Brush Wear Rate

Marvin Herche

Technical Service Manager
Special Products Division

Helwig Carbon Products, Inc. is the premier, family-owned, American manufacturer of carbon brushes, brush holders, spring assemblies, bearing protection kits, metal graphite brushes, and mechanical carbons. Since 1928, we have forged innovations that have since become industry standards and requirements. We pride ourselves on manufacturing all of our products to the highest standard and performance because we know your application depends on it!


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