Today the analysis of drive trains is performed with appropriate software such as KISSdesign (Ref. 12) which permits modeling the complete drive with all the main elements. Normally the time series is measured at the input or the output coupling. The handling of a time series for a drive train can be made in two different ways.

The “simple variant,” using the same load spectrum for each element of the drive
The “general variant,” generating individual load spectrums for different elements (such as gears, shafts, bearings) and for each stage of the drive
Use of Time Series for Drive Systems with the Simple Variant
A load spectrum of type A (Table 2) must be defined at the input or output of the system, at the location where the time series was measured. This load spectrum is then used across the drive system for all gears, shafts, and bearings. For this scope, it is preferred that torque and speed in the load spectrum are given as factors to be multiplied by the nominal values (see Figure 6). The drive train software will calculate the nominal speed/torque of every single element, and the same load spectrum, if defined with factors, can be used everywhere.

The simple variant can be used with any drive system software permitting the use of load spectrums without any further adjustment. If the torque and speed of the time series are always positive, or if some infrequent negative values can be neglected, then this method is preferred. The results for gears and bearings will be perfect, load spectrum of type A is used. For an accurate shaft verification, always load spectrum of type B should be used, otherwise, the shaft strength will not be accurate. Often shaft strength is not critical. The use of load spectrum type A—and assuming the torsion and shear as pulsating for shaft verification—will produce conservative results (on the safe side). So, if the results are satisfying, there is no need for a more complex analysis.