| Coupling Size | Torque Nm | Max. Speed (RPM) | Bore Dia MIN | Bore Dia MAX | QTY N | A | B | C | D | E | F |
|---|---|---|---|---|---|---|---|---|---|---|---|
| FBC 3 | 621 | 3600 | 16 | 50 | 4 | 160 | 107 | 51 | 5 | 75 | 114 |
The Flexible Bolt Coupling FBC 3 is a medium-duty industrial coupling designed for high torque transmission at moderate speeds. It features a larger outer diameter and deeper hub engagement than the 2A model, making it ideal for heavier industrial machinery that requires a balance between high torque capacity (621 Nm) and vibration damping.
Nominal Torque Capacity: 621 Nm
Maximum Speed: 3,600 RPM
Bore Diameter Range: 16 mm – 50 mm
Quantity of Pins (N): 4
Outer Diameter (A): 160 mm
Overall Length (B): 107 mm
The FBC 3 utilizes a four-pin configuration (N=4), but with significantly larger pins and bushes compared to the smaller models in the series. The torque is transmitted through the shear and compression of these reinforced elastomeric bushes.
The primary function of the FBC 3 is to provide a torsionally flexible connection. By using a 160 mm outer diameter (Dimension A), the coupling gains a mechanical advantage that allows it to handle 621 Nm while still utilizing a 4-pin layout, which simplifies maintenance and replacement of the flexible elements.
Increased Bore Capacity: Accommodates shaft sizes up to 50 mm, making it compatible with larger standard motor frames and gearbox output shafts.
Torsional Softness: The larger volume of the elastomeric bushes provides excellent shock absorption, protecting gear teeth and bearings from peak loads.
Simplified Maintenance: With only four pins to manage, inspection and bush replacement are faster than in higher-pin-count models like the 2A.
Robust Construction: The 160 mm flange diameter provides high structural integrity and better heat dissipation during high-load operations.
No Lubrication: Operates entirely dry, eliminating the risk of oil contamination in sensitive environments like food processing or textile manufacturing.
Heavy Industrial Pumps: Frequently used in wastewater treatment plants and large-scale irrigation systems.
Crushers and Shredders: Ideal for light-to-medium material processing where shock loads are common.
Large Belt Conveyors: Provides the necessary torque for starting under-load conveyor systems in logistics and mining.
Marine Propulsion: Used in small-to-medium vessel auxiliary drives and thrusters.
Process Compressors: Standard coupling for industrial air compressors requiring high-reliability torque transfer.
Speed Reduction: Note that the maximum speed drops to 3,600 RPM. This is suitable for 2-pole (3000/3600 RPM) motors but leaves less margin for overspeeding compared to smaller models.
Gap Setting (Dimension D): Ensure the 5 mm axial gap between the flanges is maintained during installation. This allows for the necessary axial float and prevents end-thrust on the bearings.
Hub Length (Dimension C): The 51 mm hub depth requires sufficient shaft extension to ensure the keyway is fully engaged for safe torque transmission.
Torque Verification: Ensure that 621 Nm covers the peak starting torque of the motor, particularly for high-inertia loads.
The Flexible Bolt Coupling FBC 3 is a versatile "workhorse" in the FBC range. By offering a maximum bore of 50 mm and a torque rating of 621 Nm, it bridges the gap between light-duty precision couplings and heavy-duty industrial drives. Its 4-pin design ensures it remains easy to maintain while providing the high-level vibration isolation required for modern industrial machinery.
