GMN >> Freewheel Clutches > Basics > Technology > Torque

Torque capacities

In general torque capacity is limited to:

Sprags (clamping elements):		quantity, clamping angle, stiffness
Surrounding construction:		stiffness

When torque is picked up the sprags are standing up and get jammed between inner ring and outer ring. As a reaction to this process stress is built up in the sprags as well as in the mating parts. An additional aspect is the line contact of the sprags with the raceways which can be calculated according to the theory of contact pressure by Hertz. And finally the gap between inner ring and outer ring is widened with the sprags standing up until nominal or maximum gap height is achieved.

These three aspects have to be considered at the same time - they are limiting nominal and maximum torque capacity of the complete system. See the table below:

	Gap height	Hertzian stress	max. acceptable stress
Nominal torque	Nominal gap height	4,200 MPa	σab alternating bending stress
Maximum torque	Max. gap height	4,600 MPa

Nominal torque

The values of torque capacities shown in the data sheets reflect the following situation:
All torque specifications in the catalogue and all torque specifications "M" in the data sheets correspond with the transmittable nominal torque of each freewheel clutch. Please note that there is no standard torque capacity for a clutch valid at any design. The most important parameters for defining the torque capacity of a clutch are the material to be used for customer's parts (shaft and housing) and their wall thickness.

The diagrams below show the influence of the material on the nominal torque depending on the wall thickness.

Example how to use the diagram for 20MnCr5 - case hardened, HRC 60+4, Eht = 1.3

Here are some examples:

Material	σab	Hardness
34 CrMo 4V	400 MPa	case hardened, HRC = 60+4; Eht = 1.3 mm
16 MnCr 5	400 MPa	case hardened, HRC = 60+4; Eht = 1.3 mm
20 MnCr 5	600 MPa	case hardened, HRC = 60+4; Eht = 1.3 mm
100 Cr 6	750 MPa	hardened and tempered; HRC = 60+4

With different specifications, different wall thickness, peak load conditions and higher temperature nominal torque will be decreased. Please contact our technical staff in this case.

Maximum torque

The torque capacity includes a service factor of 1.2 - 1.5. This maximum torque capacity cannot be accepted for any long-term usage.