Spring Mass system where springs also have mass

[sleventh]

hello all,
this will be my third time posting this question, i thought perhaps posting in the homework section might have it be answered. Recently I have been attempting to model a spring system (see below) where the springs themselves will have mass. I should know how to do this but i accept defeat, how do you model the potential energy and force system on two masses connected to three springs? I have read about effective mass but i fail to fully understand. Thank you all for the celerity.
_
\
/
\
[M1]
/
\
/
[M2]
\
/
_\_

In this design the spring system is vertical and grounded on both ends. Many thanks!

 

[rock.freak667]

well the potential would just be mgx+ 1/2k(x+δ)² if you plan to use Lagrange's equations to get your equations of motion.

The center of mass of the spring would move down the distance x as well as the mass m.