GMN >> Freewheel Clutches > Service > FAQ

FAQ

 

• How is the clutch designed?
• For which applications are freewheel clutches used?
• What is the difference between the 2 spring systems?
  What's the meaning of the indication "Z"?
• Which load situations is a clutch able to accept?
• What are the requirements to the mating parts?
• What has to be considered in the field of lubrication?
• Can the clutch run at high or low temperatures?
• Is it necessary to maintain or to re-grease the clutch?
• It is possible to reverse or to switch off a freewheel clutch?
• Are the RS-seals of the FK-series liquid-tight?

 

How is the clutch designed?

The basic design of a freewheel clutch is an insert element. It consists of a cage, sprags (number in relation to the shaft size) and a spring (keeps the sprags constantly in friction contact with the mating parts).

→ insert element FE

The combination of this insert element with rings, bearing support and sealing results in several complete units.

→ complete units FR, FN, FP, FPD, FRN

  

For which applications are freewheel clutches used?

→ Link to uses and fields of application

  

What is the difference between the 2 spring systems?
What's the meaning of the indication "Z"?

Our insert elements are alternatively provided with two different spring systems:

1. Meander spring, a complex system with spring load for each single sprag.
2. Z-type spring is a relative simple system, a circular spring surrounding all sprags. With the Z-spring all sprags are loaded together.

The indication "Z" is necessary to identify the spring system of the clutch. The standard system is the meander spring, the Z-spring must be indicated with the letter "Z".

General recommendations:

• Indexing element = Meander spring
• Overrunning clutch = Meander or Z-type spring
• Back-stopping = Z-type spring
  

→ More information about spring systems.

  

Which load situations is a clutch able to accept?

The maximal transmittable torque is mainly depending on the size of the clutch and on the wall thickness and stiffness of the mating parts.

→ torque

  

What are the requirements to the mating parts?

The requirements are very different depending on the chosen type. An overview can be found here:

→ assembly product range

  

What has to be considered in the field of lubrication?

Basically clutches can be lubricated with oil or grease.
The oil level should be in relation to the size of the freewheel clutch. In normal installation position, not operating, one third of the clutch should be submerged in oil.

With grease lubrication please take care that the clutch is not filled completely with grease: "Less is more" in this case. The clutch should be "greasy" - that's enough.

And generally: It is not allowed to use any lubricant with additives (for example MoS2 or graphite), which decreases the friction coefficient.

A choice of recommended and tested lubricants can be found in our indications of lubrication for:

→ spragtype clutches
→ rollerramp clutches

  

Can the clutch run at high or low temperatures?

Sealed clutches can be used up to 110°C.
Open types (no seals) are recommended for max. 160 °C.
The tempering temperature of ball bearing steel 100Cr6 (eq. AISI 52 100) (material of sprags, rings and balls) is approx. 180°C.

Care has to be taken with types including plastic cages:
Type FE 453 Z and FE 422 Z and all complete units of the same size as well as all ball bearing clutches are including a plastic cage, which can be used to max. until 140°C.

In the case of very low temperatures the right lubricant is important. A high amount of grease could cause problems with the staring process. At the FVA indexing tests at very low temperatures were made down to - 40°C. The result was no fundamental restriction.

  

Is it necessary to maintain or to re-grease the clutch?

All double-sealed types are free of any maintenance. For all other types customers have to check the contamination of the lubrication - but normally the first grease/oil lubrication with the installation is sufficient.

  

It is possible to reverse or to switch off a freewheel clutch?

No, switching-off can only be realized with a separate mechanical or electrical device. A reversal of the power flow is also not possible, GMN freewheel clutches are working only in one direction.

  

Are the RS-seals of the FK-series liquid-tight?

No, thin fluids like water, watery emulsions, petrol, light fuel oil, solvent, etc. pass the seal, pressure cannot be sealed, too. The RS-seal is designed for grease lubrication.