DYNAMIC ANALYSIS OF A SWATHER WINDROWER HEADER

The dynamic analysis of a swather/windrower header first included an i nitial analytical model that predicted natural frequencies (7.6, 8.9, 10.6, and 12.5 Hz) and associated mode shapes of the header. The mode shapes indicated that the header oscillated predominantly in the verti cal direction and the excitation force during the experimental modal t est should be applied in the vertical direction near the centre rear o f the header. An experimental modal test was then completed to determi ne the natural frequencies, mode shapes, and damping coefficients of t he header. While the header was supported in its working environment, four natural frequencies within the 7.5 to 14.0 Hz range (7.7, 9.4, 10 .5, and 12.5 Hz) and the associated mode shapes were determined. The d amping coefficients were 0.039, 0.020, 0.026, and 0.013, respectively. Inadequacies of the initial analytical model were identified by compa ring the predicted results with experimental values and steps were tak en to reduce modelling errors. The modified analytical model predicted natural frequencies that were similar to the results from the initial analytical model, but the adjusted mode shapes more closely simulated results from the experimental work.