Three flywheels, no damping

A 6th order system with three modes of vibration

This system has three linked masses.

For mode 1 IC's → x1(0)=90,  x2(0)=128,  x3(0)=90, slowest frequency
For mode 2 IC's → x1(0)=-128,  x2(0)=0,  x3(0)=128, frequency 1.8 times faster than mode 1
For mode 3 IC's → x1(0)=90,  x2(0)=-128,  x3(0)=90, frequency 2.4 times faster than mode 1

Enter initial conditions
x1(0):       x2(0):       x3(0):