Hello engineers! I have a project to measure/ obtain natural frequency of torsional vibration. Below is the detail: 1. Object measurement: Two rotor attached to one shaft and the shaft is supported by two bearing. The shaft is connected to a motor. I give the scheme below. 2. Equipment: two accelerometer, one pc/laptop include software to measure frequency response function (frf), one acquisition data machine, one impact hammer 3. Procedure 3a. First, I measure lateral frf (ordinary frf/ translasional frf). I give impact in the two holder (that has bearing). 3b. Second, I measure torsional frf by give impact in rotor so it will be like that I give torque to the system. 3c. We compare the result 3a and 3b and look to frequency where has high amplitude in 3b (torsional) but not in 3a (lateral). So the frequency is torsional natural frequency. My question is: 1. Is my procedure valid? 2. Can you give me some literature that related to my project? 3. What is your advice and tips to my project? http://mechanical-engg.com/forum/uploads/monthly_2015_11/torq.PNG.80d4fa9613b4f538e41024dcb50494ef.PNG [Broken] Sorry for my english Thanks for answering my question!