Beam Spin Ratio

Double-click to select the beam and enter/edit the spin-ratio value.

It is defined as code 9.2. It defines fixed spin ratios for use in determining spin speeds or whirl speeds. For unbalance response analysis in the whirl frame, the spin ratio is defined is the ratio of a beam's spin speed to the independent speed variable defined with UNBAL-RESP (code 95.)

For undamped whirl speed calculation in the whirl frame, the spin ratio is multiplied by the system whirl ratio defined in WHIRL-RATIO (code 93.) to define the whirl ratio for each beam. For fixed frame analysis, the spin speed of each beam is the spin ratio multiplied by the independent speed variable in code WHIRL-SPDS (code 94.).

Beam spin reference

Double-click in the listbox to select the reference beam.

It is defined as code 9.3. The selected beam is considered a reference beam with spin ration 1.0. If specified the spin ratios defined by Beam-spin (code 9.2) are divided by the spin ratio for beam Nref (in this example it is beam 2), setting it to 1.0 and normalizing others to Nref.

A screen dump from the roda input file is shown below.