A flexible gearbox coupling provides a damper between the gearbox and propeller shaft to isolate torsional vibration and reduces the shock from forward and reverse gear changes. A flexible gearbox coupling works in conjunction with the engine mounting system to provide the softest element in the shaft assembly improving performance. In addition, they act as a sacrificial link that is designed to fail before gearbox damage occurs. Poly Flex flexible gearbox couplings are designed to cover a large percentage of gearboxes, such as but not limited to Twin Disc, ZF, Dong-I, Borg Warner, Bukh, Newage, Paragon, Technodrive, Volvo and Yanmar. While Poly Flex flexible gearbox couplings are designed for marine use, they are utilised in many industrial coupling driveline applications too.
Flexible gearbox couplings are simple and relatively inexpensive devices that are not difficult to maintain, yet some fail prematurely. These failures can happen despite the flexible gearbox coupling having the specifications to tolerate the application and cope with the operating conditions such as temperature extremes and humidity. Below is what needs to be remembered when maintaining a flexible gearbox coupling.
While flexible gearbox couplings are designed to allow for misalignment under thrust, excessive misalignment between flanges is the most common reason for failure. Alignment is often not carried out correctly. Poly Flex state all alignment and fitting procedures of flexible gearbox couplings must be carried out while the vessel is in the water. If it is not possible to fit the flexible gearbox coupling whilst in the water, final alignment and tightening procedures must be carried out after launching the vessel. A common sign of misalignment is heat build-up in the flexible gearbox coupling. It shouldn’t be any hotter than the ambient temperature in the engine room. Misalignment increases stress on the drivetrain, decreases the capacity and life of the coupling and causes premature wear of stern bearings. Poly Flex recommends the alignment be checked every 6 months if mounted on rubber mounts (due to design and material of rubber mounts, which tend to settle) and every 12 months if mounted on Poly Flex mounts.
- Always Follow The Manufacturer Installation Instruction:
All Poly Flex flexible gearbox couplings come with installation instructions for reference. Installing a flexible gearbox coupling without following the installation instructions can lead to premature failure, warranty voiding and it losing its fail-safe coupling properties. It is urged to refer to the specific manufacturer’s installation directions, adhere closely to them and not rush the process.
- Incorrect Flexible Gearbox Coupling Specifications:
Not all flexible gearbox couplings are the same. There are many types and for optimum power transmission the right flexible gearbox coupling must be selected. If this doesn’t happen the results can be premature flexible gearbox coupling failure. If the operation is experiencing frequent coupling failure despite the alignment being in order, it is recommended that the system conditions at failure be documented so a more appropriate flexible gearbox coupling can be installed to suit conditions such as the load, torque, temperature, or horsepower. Poly Flex has an extensive transmission cross reference table, please click here, and all flexible gearbox couplings range in polyurethane durometer hardness and can be changed to suit all applications. Poly Flex also has CNC machining capability to manufacture adapter plates for larger flexible gearbox couplings to be installed.
- Poor System Maintenance:
Without proper maintenance the efficiency and effectiveness of a system will be compromised. A flexible gearbox coupling is just as important as a gearbox, pump, bearing assembly or any other component requiring precision and must be given the appropriate level of care. A regular maintenance schedule should be followed and carried out often.
- Lack Of Information:
The more knowledge about why flexible gearbox couplings fail allow fewer chances to experience issues. The better informed the maintenance team are about the importance of the correct specification, assembly and maintenance of flexible gearbox couplings allows more reliable performance and less downtime.
Poly Flex has been proudly designing and manufacturing Australian made flexible gearbox couplings for over 40 years. With a strong focus on customer service Poly Flex has an extensive list of distributors and dealers well versed in the proper installation and maintenance of our product range.
For more information regarding Poly Flex flexible gearbox couplings, please click here. To find a distributor or dealer near you please click here. Alternatively, contact us today regarding any enquiries.