Indian Institute of Space Science and Technology
AE223: Kinematics and Dynamics of Mechanisms
Tutorial 11: Balancing
Aerospace Engineering
02­04­2013
1. A circular disc mounted on a shaft carries three attached weights of 40N, 30N and 25N at
radial distances of 75mm, 85mm and 50mm and at the angular positions of 45 0, 1350 and
2400 respectively. The angular positions are measured counterclockwise from the reference
line along the x-axis. Determine the amount of the countermass at a radial distance of 75mm
required for the static balance.
2. A gas turbine rotor carries four blade disks, as shown in Fig.Q2, has unbalance in three rotors.
The shaft turns in bearings in plane P and Q. Relative to the reference frame shown, the unbalances
of the blade disks are respectively UA= 0.8m-kg at 100, UB= 0.45m-kg at 1900, UD= 2.8m-kg at 3200.
The rotor is to be balanced by adding material on disk A at radius and on disk D at radius. Calculate
the mass that must be added at each location and the angular position at which it must be added.
Assume the maximum radius at which the mass can be added is 0.5m from the shaft axis.
3. The device shown in Fig. Q3 is used to balance fan blade/hub assemblies running at 600rpm. The
centre distance between the two bearings on the machine is 250mm. The left edge of the fan hub
(plane A) is 100mm from the centerline of the closest bearing (at F2). The hub is 75mm wide along
its axis and has a diameter of 200mm along the surfaces where balancing weighs are fastened. The
peak magnitude of force F1 is 0.5 N at a phase angle of 300 with respect to the rotating x’ axis.
Force F2 has a peak of 0.2N at a phase angle of 1300. Calculate the magnitude and location with
respect to the x’ axis of balance weights placed in plane A and B of the hub to dynamically balance
the fan assembly.
Fig. Q2
Fig. Q3