Pattern speed of vertical distortion during and after buckling as function of amplitude of oscillations along the bar. The left panel shows the approximately constant pattern speed during buckling, assuming the evolved $f_z^{\prime }$ and unevolved f_x. The middle panel shows the strongly decreasing pattern speed after buckling with evolved $f_z^{\prime }$ and $f_x^{\prime }$. The right panel shows $(f_x^{\prime }+f_{\mathrm{p}})/3$, which turns out to be equal to the pattern speed after buckling.