The RP-B Enlarged Bore Jaw Flexible Coupling features steel hubs for heavy-load drive units including lifts, rolling mills, and construction machinery. Sharing the RP-A hub geometry but accommodating larger bore diameters up to Φ220 mm, it delivers up to 18,650 N·m torque at compact overall dimensions with zero maintenance.
The RP-B Enlarged Bore Jaw Flexible Coupling extends the proven RP jaw-coupling platform to demanding heavy-duty applications where larger shaft diameters are the norm. By replacing the cast-iron or cast-aluminium hub of the standard RP-A with a steel hub, the RP-B resists the higher bending stresses associated with large-bore installations — particularly important in lifting machinery, rolling mills, and heavy construction equipment where both transmitted torque and shaft diameter are substantially greater than in general mechanical engineering.
The overall coupling geometry and marking convention are identical to the RP-A, allowing engineers already familiar with the standard series to specify the RP-B with confidence. The elastomeric spider remains a polyurethane element rated at 92 ShA (nominal torque table values), and the same spider used in the RP-A fits the corresponding RP-B hub size, simplifying spare-parts inventory management. Maximum bore extends to Φ220 mm on the RP180B model, covering virtually all shaft sizes encountered in industrial drives up to 18,650 N·m.
| Model | Torque (N·m) | Speed (rpm) | Bore d (mm) | L (mm) | D (mm) | E (mm) | Weight (kg) |
|---|---|---|---|---|---|---|---|
| RP19B | 10 | 19000 | 6–25 | 25 | 66 | 16 | 0.328 |
| RP24B | 35 | 14000 | 8–35 | 30 | 78 | 18 | 0.68 |
| RP28B | 95 | 11800 | 10–40 | 35 | 90 | 20 | 1.16 |
| RP38B | 190 | 9500 | 12–48 | 45 | 114 | 24 | 2.27 |
| RP42B | 265 | 8000 | 14–55 | 50 | 126 | 26 | 3.57 |
| RP48B | 310 | 7100 | 15–60 | 56 | 140 | 28 | 4.80 |
| RP55B | 410 | 6300 | 20–70 | 65 | 160 | 30 | 7.87 |
| RP65B | 625 | 5600 | 22–75 | 75 | 185 | 35 | 10.89 |
| RP75B | 1280 | 4750 | 30–90 | 85 | 210 | 40 | 17.73 |
| RP90B | 2400 | 3750 | 40–100 | 100 | 245 | 45 | 29.60 |
| RP100B | 3300 | 3350 | 50–110 | 110 | 270 | 50 | 43.0 |
| RP110B | 4800 | 3000 | 60–125 | 120 | 295 | 55 | 58.6 |
| RP125B | 6650 | 2650 | 60–145 | 140 | 340 | 60 | 88.4 |
| RP140B | 8600 | 2350 | 60–165 | 155 | 375 | 65 | 120.8 |
| RP160B | 12800 | 2000 | 80–190 | 175 | 425 | 75 | 179.1 |
| RP180B | 18650 | 1800 | 85–220 | 195 | 475 | 85 | 261.0 |
The RP-B's steel hub construction and enlarged bore range make it the preferred choice wherever shaft diameters exceed the practical limits of standard cast hubs. Key sectors include:
For applications where misalignment compensation is more critical than bore size, the RP-S double-elastomer coupling may be more appropriate. See also the full coupling product range for a comprehensive comparison.
🇧🇪 Belgium — Lift Manufacturing
A lift manufacturer in Liège standardised on the RP-B range across their hydraulic and traction drive lines. The steel hub provided the necessary fatigue strength for the frequent start-stop cycles inherent in lift operation, and the 92 ShA spider absorbs the startup jerk effectively.
★★★★★
"No coupling failures in four years across a fleet of 340 installations." — Technical Director
🇵🇱 Poland — Steel Mill Drive
A rolling-mill drive upgrade project in Katowice required couplings capable of handling shaft diameters up to 165 mm with peak torques during strip breakage events. RP125B and RP140B units were selected; the steel hub held up under repeated overload without any permanent deformation.
★★★★★
"Delivery of matched bore pairs was accurate to within 0.02 mm, which simplified our assembly greatly." — Drive Engineer
🇦🇺 Australia — Mining Conveyor
A mineral processing operation in Queensland fitted RP-B couplings on ten overland conveyor head drives, replacing competitor couplings that had suffered hub cracking. The steel hub design eliminated cracking, and the first spider replacement was not required until after 26 months of continuous operation.
★★★★☆
"Spider replacement in the field is straightforward — critical for remote-site operations." — Maintenance Superintendent
The steel hub of the RP-B resists the higher bending stresses and fatigue loads that arise when bore diameters are large relative to the hub wall thickness. Cast-iron or aluminium hubs used in the RP-A are adequate for smaller bore sizes but can develop fatigue cracks under repeated overloading at large diameters. For shaft diameters above approximately 80–100 mm in demanding duty cycles, the RP-B is the recommended choice.
Yes, for matching size designations the elastomeric spider is identical between the A and B variants. This significantly simplifies spare-parts procurement and stocking — a single spider size covers both hub types, reducing the total number of part numbers required in a maintenance inventory.
The RP180B, the largest model in the B series, accommodates shaft bores from 85 mm up to 220 mm and transmits a nominal torque of 18,650 N·m at up to 1,800 rpm. Custom bore machining to specific dimensions within the stated range is available on request.
Yes. Bore diameter, keyway dimensions, and sleeve type can all be adapted to customer specification. Please provide shaft drawings and torque requirements when requesting a quotation so that the most appropriate configuration can be recommended.
The polyurethane elastomeric spider absorbs and dissipates the kinetic energy of acceleration and deceleration shocks through controlled elastic deformation. The steel hub prevents the underlying bending stress from propagating fatigue cracks in the hub wall — the primary failure mode seen with cast hubs in lift drives subjected to frequent stop-start cycles over many years of service.
RP supplies industrial coupling solutions to OEM manufacturers, system integrators, and aftermarket distributors. Custom bore specifications, special material grades, and volume pricing are all available. Contact our technical sales team to discuss your application.
Explore the complete jaw coupling series or the full coupling catalogue.
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