A rigid object, with no torques applied to it, rotates with constant angular momentum. But its angular velocity $\omega$ is not constant in general; it follows the differential equations $$\frac{d\omega_{12}}{dt}=\frac{a_1^2-a_2^2}{a_1^2+a_2^2}\big(\omega_{13}\omega_{23}+\omega_{14}\omega_{24}\b...