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RPM Shouldn’t be a Limiting Factor

Our high torque capacity FE 8000 sprag clutch insert elements are unlike any other clutch of its kind on the market today. Here is what sets it apart:

A. Our sprags have a unique design.

  • Sprags will engage at any speed, there is no RPM limit.
  • Sprags have a constant clamping angle for increased reliable engagement.

B. More torque.

  • Our FE 8000 has almost double the torque capacity than the leading competitor.

C. Single cage design.

  • More sprags, per clutch, than any other clutch on the market.
FE 8000

Download our FE 8000 Case Study!

See how one company partnered with our engineering team and eliminated their winch failures.

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Part Number Spring Type Bore Diameterd [mm]Outer DiameterD [mm]WidthW [mm]Nominal TorqueT [N⋅m]Nominal TorqueT [ft⋅lb]  

No RPM Limits: How The FE 8000 Series Works

Diagram indicating clamping direction of a GMN sprag clutch. There are arrows pointing counter-clockwise on the outer part of the clutch, and arrows pointing clockwise on the inside of the clutchWhen idle, no torque is being transmitted, the sprag assembly is rotating.

With other clutch brands, when the clutch is operating too fast the centrifugal force causes the sprags to lay down and lift off the shaft. That’s why you will see an RPM limit on their clutches.

BUT with the GMN FE 8000 sprag clutch, we don’t have that problem.

Our sprags are designed with a unique geometrical shape that actually uses the centrifugal forces in their favor! When centrifugal forces increase, our sprags stand up on the shaft, which produces a constant contact on the shaft at any speed (RPM). Therefore, our FE 8000 has no limiting speed issues.

We know there is a “wildcard” when we talk about RPM, and that’s lubrication.

So book 20 min on our engineer’s calendar and we’ll walk you through all the “geeky” details including system requirements, lead times, and pricing.

Clamping & The Engagement Curve

A drawing of the clamping angle in a sprag clutch next to a sprag clutch mating part

The unique geometric design of the sprag produces a constant engagement curve. A specific clamping angle (αa, αi) results when the sprags are in contact with the mating parts. This part of the engagement curve is called the operating zone.

Learn more about clamping & the engagement curve

Nominal Torque

For optimal torque transmission there are three key components:

  1. Stiffness of sprags, shaft and housing for minimal deflection
  2. Gap height requirements need to be met so the sprags aren’t standing up too much before engagement
  3. The line contact for Hertzian pressure needs to be tight

The rules for gap height and Hertzian pressure are:

  • Nominal torque: Gap height 8.490 mm OR Hertzian pressure of 4,200 MPa
  • Max. torque: Gap height 8.600 mm OR Hertzian pressure of 4,600 MPa

Learn more about torque & Hertzian pressure

Torque Capacity

GMN Series 8000 nominal torque diagram

Wall thickness is the key factor for measuring stiffness in the shaft and housing. The chart below shows what happens to the stress and torque limits with respect to wall thickness. We recommend a D/DL value of at least 1.4

Learn more about wall thickness & material requirements

Application Requirements For The FE 8000 Series

  1. Hardened and ground mating parts
    • HRC : 60 +4
    • Surface (Rz): < 2.5 µm
    • Hardness Depth: 1.3 mm
  2. External Bearing support
    • Clamping elements don’t hold concentricity
  3. Lubrication
    • No additives in the lubrication or it will prevent sprag engagement

Contact GMN Bearing USA!

Contact our onsite engineers for help with your FE 8000 sprag clutch applications.

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