Selection Procedure

STIEBER SOLUTIONS: ALWAYS THE RIGHT CHOICE.

Unit selection is initially determined by the type of application: OC Overrunning clutch, IC Indexing clutch, BS Backstop. Different technical information is required for each one of them. Mounting details and lubrication requirements finally determine the unit selected.

The information required for each type of application is as follows:

Overrunning Clutch
Indexing Clutch
Backstop

Overrunning Clutch

  • Type of motor
  • Nmstart/Nmnominal of E-motors
  • Internal combustion engines, please consult Stieber
  • Nominal driving torque
  • Range of driving speed
  • Inertia „J“ of the driven masses
  • Range of overrunning speed
  • Number of start during service life
  • Shaft diameter

Indexing Clutch

  • Number of cycles/min
  • Index angle
  • Nominal torque
  • Inertia „J“ of the driven masses
  • Accelerations of the driving member
  • Number of indexes during service life
  • Shaft diameter

Backstop

  • Static reverse torque
  • Maximum dynamic reverse torque due to elasticity of the locked parts (elastic belts, shafts more than 3 meters long)
  • Range of overrunning speed
  • Number of torque applications during service life
  • Shaft diameter
Overrunning Clutch Diagram
Indexing Clutch Diagram
Backstop Illustration

THE SELECTION PROCEDURE: WE ADVISE, YOU DECIDE.

If we have the data previous described, Stieber can make the most accurate selection. If all of the information is not available, or if you want to make a selection yourself, the following service factor procedure may be used.

Note: The following method and the service factors used are only a guide based on experience and cannot cover all situations. We cannot accept responsibility for incorrect selection resulting from the use of these tables.

Step 1 TORQUE SELECTION

The first step is to calculate the catalogue torque (TKN) of the unit to be chosen. This torque is derived from the application nominal torque (Tappl) multiplied by a (service factor) S.F. depending on the function of the freewheel and working conditions.

Nominal torque of the application: Normal Torque Calc The unit catalogue torque will be: Torque Calc

Note: All the units shown in this catalog can support a maximum torque equal to 2 times the catalogue torque TKN indicated in the respective data tables.

Torque Chart

The following curve may be used as a guide to determine the relationship between torque transmitted and the number of cycles (applications of this torque) the unit would withstand in its life time. Average values are shown.

SERVICE FACTORS.

View Service Factors

Application INDEXING
Indexing speed
Type of freewheel
Roller type
Sprag type
Over 150 strokes/min 3.0 4.0
Angle > 90° | Over 100 strokes/min 2.5 4.0
Angle > 90° | Less than 100 strokes/min 2.0 3.5

Application BACKSTOP

Driving machine
Driven machine
Elastic conveyor belts
with risk of jam
Pump drives with more
than 5 metres shaft
Fans
Other machines
No overloads Dynamic overloads
Motors with hydraulic couplings 1.3 1.6 0.5 1.0 1.5
Asynchronous motors with direct start1 1.6 1.6 0.5 1.0 1.5
Steam or gas turbine - 1.6 0.5 1.0 1.5
Internal combustion engine 1.6 1.6 0.5 1.0 1.5

Application OVERRUNNING

Driving machine
Working conditions
Starting torque not higher
than nominal
Smooth drive.
Starting torque up to 2
times running torque.
Moderate load variations.
Starting torque 2 to 3 times
running torque.
Load variations.
High starting torque.
High load torque
variations.
DC - motor.
AC - motor with soft start or hydraulic
coupling
1.3 1.5 1.8
Asynchronous
motor with direct
start
Speed reduction
between motor &
freewheel < 4
- 2.5 3.0 4.0
Speed reduction
between motor &
freewheel > 4
- 1.5 1.8 2.3
Steam or gas turbine 1.3 1.5 - -
Internal combustion
Eninge
Petrol 4 cyl.or
Diesel < 6 cyl.
4.0 5.0 Contact Stieber -
Diesel N 6 cyl. 5.0 6.0 Contact Stieber -

Model Selection

Step 2 MODEL SELECTION

When the catalogue torque is known, the model will be selected from the following criteria:

  • Built-in or self-contained design
  • Driving and overrunning speed limits
  • Dimensions
  • Lubrication and maintenance

Please refer to the selection table for a guide to selection. The product range is presented in this order:

SELF-CONTAINED BALL BEARING UNITS (CSK RANGE)

General purpose, economical units for light applications. Grease lubricated, maintenance free. With or without key(s) mounting to shaft and housing.

BUILT-IN UNITS

Roller types with inner and outer races (A-series) or only a cage (DC sprag series). Bearing support, lubrication and maintenance must be provided.

SELF-CONTAINED UNITS

  • Low speed, grease lubricated, maintenance free (RSBW, AV series)
  • Medium overrunning speed inner race. High overrunning speed outer race. Roller types, oil lubricated. (AL, GFR series).
  • High overrunning speed inner race. Medium overrunning speed outer race. Sprag types, oil or grease lubricated (SMZ, FS, FSO series).
  • High speed, high power, for continuous duty encased overrunning clutches (AL..G, CEUS.., BC..MA series).

CENTRIFUGAL LIFT OFF SPRAG TYPES

Special overrunning clutches and backstops contact free during overrunning. Please be aware of the speeds permissible in driving and overrunning modes.

  • Built-in units: Low lubrication requirement. Accept a large range of lubricants (RSCI series).
  • Self-contained units: Grease lubricated, long life and maintenance free (RIZ series).