How do i simulate/model the shaft between a motor and a load in matlab? $$ reward.

I need to be able to model the shaft between a motor and load, doing this i am then able to input the stiffness and viscious friction of the shaft.

Hence a lagging load depending on how stiff the shaft is.

The photo represents what i have already although i feel the results are not correct. bs = viscous friction ks= shaft stiffness j = rotor inertia

Torque seen at the load(i think) is T=k(theta1 - theta2) theta1 is the position of the rotor and and theta2 is the consequential position of the load

If someone can design this i am happy to pay them for there efforts