Lateral Vibration Prediction of Drivelines Having a Flexible Coupling

This work provides a theoretical analysis of the natural and forced lateral vibration in a driveline having a flexible coupling and universal joints. The analysis is specific to the front driveline common in many off-highway vehicles which usually consists of a flexible coupling at the engine flywheel, the driveshaft, and one or two universal joints. A torsionally flexible coupling is often needed in a front driveline to suppress torsional vibration. The problem is that most torsionally flexible couplings are also inherently flexible in their radial and cocking directions. These additional directions of flexibility, compounded by the presence of universal joints, can result in unexpectedly low lateral natural frequencies of the driveline. With a few axial dimensions, mass properties of the driveline, and stiffness properties of the flexible coupling, this work provides simple, closed-form calculations for the lowest lateral natural frequencies. This work also investigates the lateral disturbances to the driveline that can result in synchronous whirl.