How do I make a simple model to simulate a banked turn?
It's computed with centripetal force:

$$F_C = m \cdot V \cdot \omega $$


m = aircraft mass [kg]
V = aircraft speed [m/s]
$\omega$ = rate of turn [rad/s]


Centripetal force is a function of bank angle $\Phi$ and lift, or mass and flight path. For a coordinated, level turn:



Vertical lift $L \cdot cos(\Phi)= m \cdot g$ and turning lift $L \cdot sin(\Phi) = F_C$, so in a steady turn

$$ F_C = m \cdot g \cdot tan(\Phi)$$

$$\omega = \frac{g}{V} \cdot tan (\Phi) \tag{Steady Turn}$$  

A more general equation, also valid for 90 degree bank angles and not concerned with the aircraft staying up in the air, can be found by considering horizontal forces only:

$$ \omega = \frac {L \cdot sin(\Phi)}{m \cdot V} \tag{always} $$

And then if you assume that lift L is still equal to weight $m \cdot g$ which means the aircraft is losing altitude in this turn, you're almost back at the Steady Turn equation but now with a sin instead of a tan.

The above is for SI units. For aircraft units with feet and knots, please check this answer, and here is one that introduces lift coefficient into the equation.