| Coupling Size | Torque Nm | Max. Speed (RPM) | Bore Dia MIN | Bore Dia MAX | QTY N | A | B | C | D | E | F |
|---|---|---|---|---|---|---|---|---|---|---|---|
| FBC 4A | 1241 | 3000 | 20 | 70 | 6 | 191 | 125 | 60 | 5 | 105 | 114 |
The Flexible Bolt Coupling FBC 4A is a high-capacity variant of the FBC 4 frame size. While it shares the same physical dimensions and bore capacity as the standard FBC 4, it utilizes a six-pin configuration to increase its torque rating by 50%. This makes it an ideal solution for heavy-duty applications that require maximum torque density without increasing the overall footprint of the coupling.
Nominal Torque Capacity: 1,241 Nm
Maximum Speed: 3,000 RPM
Bore Diameter Range: 20 mm – 70 mm
Quantity of Pins (N): 6
Outer Diameter (A): 191 mm
Overall Length (B): 125 mm
The FBC 4A utilizes six high-tensile steel pins (N=6) instead of the four pins found in the standard FBC 4. By increasing the number of pins, the torque load is distributed over a larger surface area of elastomeric bushes.
As the driving flange rotates, the 1,241 Nm of torque is transferred through the compression of these six bushes. This multi-pin arrangement provides a "smoother" torque transfer and enhances the coupling's ability to dampen torsional vibrations. The design maintains the critical 5 mm gap (Dimension D) to ensure that axial movement in the shafts does not lead to metal-to-metal contact or bearing thrust.
High Torque Density: Delivers over 1,200 Nm of torque within the same 191 mm diameter as the FBC 4, providing an easy upgrade path for systems needing more power.
Enhanced Redundancy: With six pins, the coupling offers greater reliability; the wear of a single bush has a less dramatic impact on the total system balance than in lower pin-count models.
Versatile Bore Range: The 70 mm maximum bore capacity allows it to be fitted to a wide variety of heavy industrial motor shafts.
Maintenance-Free: Requires no grease or oil. The flexible bushes can be inspected visually and replaced without moving the connected machinery (depending on the specific installation setup).
Vibration Isolation: The six-bush design is particularly effective at absorbing the shock loads common in heavy-start or reciprocating machinery.
Large Slurry Pumps: Used in mining and dredging where high torque and shock resistance are mandatory.
Heavy Conveyor Systems: Ideal for main drive pulleys on long-distance material handling belts.
Industrial Mixers: Powering high-viscosity mixing vats in the chemical and food industries.
Medium-Sized Crushers: Used in recycling and aggregate processing where the coupling acts as a protective buffer for the motor.
Large Fan Drives: Specifically for mine ventilation or large-scale industrial cooling where high reliability is required.
Torque vs. Speed: While the torque capacity is high (1,241 Nm), ensure the operating speed does not exceed 3,000 RPM.
Hub Depth (Dimension C): With a 60 mm hub length, ensure the shafts are long enough to provide full support for the keyway to prevent shaft shearing under high torque.
Interchangeability: The FBC 4A is physically interchangeable with the FBC 4 regarding its outer diameter (191 mm) and length (125 mm), allowing for a direct torque-capacity upgrade if system loads increase.
Bush Material: Ensure the elastomeric bushes are compatible with the local environment, particularly if exposed to extreme temperatures or chemicals.
The Flexible Bolt Coupling FBC 4A is the high-performance choice for the 191 mm frame size. By utilizing a 6-pin design, it provides a robust 1,241 Nm of torque capacity, making it one of the most efficient couplings in its size class. It is perfectly suited for heavy-duty industrial applications that demand high torque, large bore capacity, and superior vibration damping.
