The shaft is massless. A thin attached triangular mass ‘m’ is mounted on the shaft. Rotational speed of the shaft is ω. Neglect weight effect of attached mass. Bearings are at A and B. Take Z- axis along the shaft axis. X- axis is vertically downward. Y – axis is horizontal. Take origin at self-chosen point on the shaft. Questions 1. Look at the problem and tell whether it is a problem of pure static unbalance, pure dynamic unbalance, mixed unbalance.
FOR FIG REFER ATTACHED FILE
The shaft is massless. A thin attached triangular mass ‘m’ is mounted on the shaft. Rotational speed of the shaft is ω. Neglect weight effect of attached mass. Bearings are at A and B.
Take Z- axis along the shaft axis. X- axis is vertically downward. Y – axis is horizontal. Take origin at self-chosen point on the shaft.
Questions
1. Look at the problem and tell whether it is a problem of pure static unbalance, pure dynamic unbalance, mixed unbalance.
2. Use moment equation about ‘A’ and force equation to obtain the bearing reactions at ‘A’ and ‘B’.
3. Replace the attached body by concentrated mass particle of mass equal to the body at its centre of mass. What will then be the bearing reactions. Look at the solution of part 2 and give your answer.
4. Put centrifugal forces in the model of part 3 and obtain bearing reactions using equilibrium equation.
5. Rotate the shaft by 90 degrees and write the bearing reactions by observation of previous result.
6. Under what practical condition is the neglect of weight of attached bodies justified.
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