Engine flywheel couplings have to strike a delicate balance when it comes to stiffness. On the one hand, they have to be rigid enough to transmit torque efficiently and avoid resonance problems. On the other, they have to be flexible enough to handle any misalignment between the motor and the drive shaft.
The Ringfeder Power Transmission TSCHAN TNR Coupling consists of an aluminum housing and steel hub separated by a set of cylindrical elastomer inserts. Contained in opposing machined grooves in the hub and housing, the elastomer inserts deform under shear loads as the coupling transmits torque. Depending on the application requirements, the coupling can have one or two rows of inserts, linked in series by a grooved aluminum buffer link.
The TNR coupling delivers a wide range of torsional stiffness values for a given coupling size. Changing the stiffness is simply a matter of varying the arrangement and material properties of the elastomer inserts. For example, the smallest TNR coupling has torsional stiffnesses from 900 to 5,900 Nm/rad across a torque range of 160 to 510 Nm.
This ability to achieve many different stiffness values can be indispensable when you need to avoid resonance issues in your powertrain designs—while keeping the number of coupling sizes you use to a minimum. Resonance occurs when the operating frequency of the system equals its natural frequency—which is determined largely by the moments of inertia and stiffness of the engine, the rotating output shaft, the couplings and the driven load. Without some sort of damping or operating frequency adjustments, resonance can spiral out of control,
causing damaging vibrations.
Oftentimes, the application requirements will lock you into a specific engine and set of operating frequencies. But the coupling can easily be specified with an eye toward managing resonant frequencies and preventing your engine-driven equipment from developing a bad case of the shakes.
That’s where the TNR coupling comes into play. By adjusting the stiffness values you can give just the right amount of damping to ensure that the driven system’s operating frequencies do not equal its natural frequency. Engineers have used this strategy for years with rubber couplings, but the TNR makes it far easier to adjust stiffness—both in terms of the granularity of the adjustment and the range available within a given coupling size. Manage misalignment. The TNR design also comes in handy when you need to accommodate for any misalignment between the motor’s output shaft and the rest of the drive train. The same elastomer inserts that allow you to dial in a precise torsional stiffness can also provide some flexibility to offset shaft misalignment. You may have to sacrifice some torque transmission efficiency if you pick softer elastomer inserts that can maximize the misalignment
compensation within ±0.5 degrees.
TNR couplings typically weigh about 20% less than an equivalent rubber coupling. Keep in mind, however, that equivalent means same performance, not necessarily same size. Thanks to its wide torque and stiffness ranges, TNR couplings have a power density advantage that often allows a smaller, lighter model to replace a larger, heavier rubber coupling. This power density edge can make a big difference in mobile diesel applications, such as
heavy equipment or trucks.
Ringfeder
www.ringfeder.com