A mechanical model is a simple device made out of helical springs. Using the mechanical model one can visualize the difference between the first and the second order phase transitions. The analogy between the mechanical model and phase transitions in liquid crystals will be discussed. The parameters of the simple device (length, frequency, amplitude, tilt, etc.) can serve as an analogy for the parameters used in theories of phase transitions. The simple mechanical model is also convenient for the presentation and visualization of the dynamics near SmA-SmC phase transition in liquid crystals.