Spring TYPE4 - 1 DOF Spring (/PROP/SPRING)
Spring TYPE4 is a simple physical spring, physical dashpot or parallel spring and dashpot.
![](../../../images/solvers/guide_spring-type4.png)
Figure 1. Spring TYPE4 - Time Step
Critical spring time step ensures the stability of explicit time integration scheme, but it does not ensure a high accuracy on spring vibration behavior. Only two time steps are available during one vibration period of a free spring. To reproduce the true sinusoidal behavior, reduce the time step by a factor of at least 5. If the spring is used to connect two parts together, the spring vibration period increases and the default spring time step ensures stability and accuracy.
![](../../../images/solvers/guide_initial-pos.png)
Figure 2. Co-linear Forces in Spring TYPE4
![](../../../images/solvers/springs_instability.png)
Figure 3. Instability of a Zero Length Spring
For further information, refer to the Radioss Theory Manual.