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The balancing of rotating bodies is important to avoid vibration. In heavy industrial machines such as gas turbines and electric generators, vibration can cause catastrophic failure, as well as noise and discomfort. In the case of a narrow wheel, balancing simply involves moving the center of gravity to the centre of rotation
A balancing machine is a measuring tool used for balancing rotating machine parts such as rotors for electric motors, fans, turbines, disc brakes, disc drives, propellers and pumps. The machine usually consists of two rigid pedestals, with suspension and bearings on top supporting a mounting platform.
A static balance (sometimes called a force balance [2] [3]) occurs when the inertial axis of a rotating mass is displaced from and parallel to the axis of rotation.Static unbalances can occur more frequently in disk-shaped rotors because the thin geometric profile of the disk allows for an uneven distribution of mass with an inertial axis that is nearly parallel to the axis of rotation.
Propeller whirl flutter is a special case of flutter involving the aerodynamic and inertial effects of a rotating propeller and the stiffness of the supporting nacelle structure. Dynamic instability can occur involving pitch and yaw degrees of freedom of the propeller and the engine supports leading to an unstable precession of the propeller. [13]
Betz (1921) provided an approximate correction to momentum "Rankine–Froude actuator-disk" theory [4] to account for the sudden rotation imparted to the flow by the actuator disk (NACA TN 83, "The Theory of the Screw Propeller" and NACA TM 491, "Propeller Problems"). In blade element momentum theory, angular momentum is included in the model ...
The crankpin-and-rods weight on the wheels is in a plane outside the wheel plane location for the static balance weight. Two-plane, or dynamic, balancing is necessary if the out-of-balance couple at speed needs to be balanced. The second plane used is in the opposite wheel.
The innovation introduced with the screw propeller was the extension of that arc through more than 360° by attaching the blade to a rotating shaft. Propellers can have a single blade, but in practice there is nearly always more than one so as to balance the forces involved. Archimedes' screw
where g is the acceleration of gravity, and the are the weights of each segment, and the are the static deflections (under gravitational loading only) of the center of each segment. Generally speaking, if n is 2 or higher, this method tends to slightly overestimate the first natural frequency, with the estimate becoming better the higher n is.
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