Balancing a Rotor

This example shows how to investigate an unbalanced rotor and balance it with rotating counterweights. 

In this example, the goal is to minimize the radial deflection of the rotating shaft. At the starting point, a shaft with two disks is rotating around its own axis. This system is not balanced, which will cause an unbalance, generating a deflection of the shaft. This will limit how fast the rotor can spin safely. The system is then balanced by adding two counterweights on two disks, balancing the system. For more information on how this can be calculated, read this blog post.

Analysis

The angular velocity of the shaft is increased over time, and the deflection caused by the unbalances will therefore also increase, depending on how close the system is to its eigenfrequency. Figure 1 shows the deflection of the two disks after balancing.

 Figure 1: Balanced disk deflections.

Due to the balancing disks, these deflections are rather small. Compared to a system without the balancing disks. Figure 2 shows the deflection after running the unbalanced system (this is done by setting the top-level parameter balanced to false and then simulating). Note the values on the y axes, which are much larger than for the balanced system.

Figure 2: Unbalanced disk deflections.

This example is discussed in great detail in this blog post.