Critical Speeds of Rotating Shafts with Single Loads Equations and Calculators
Bearings
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Critical Speeds of Rotating Shafts or Mass Review
Critical Speeds of Rotating Shafts with Single Loads: When calculating critical speeds, the weight or mass of the rotating cylinder or shaft is assumed to be zero or add 1/2 to 2/3 of the rotating shaft to the load mass. Keep in mind that a shaft with more than one load or distributed loads may have an infinite number of critical speeds. Typically, the first critical speed is most important for your design.
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Load Configuration |
Equation |
Two Concentrated Loads General Equation * | |
Where:
N_{1} | = first critical speed, RPM |
N_{2} | = second critical speed, RPM |
Δ_{1} | = static deflection, (in, m) at W_{1} if shaft is horizontal |
Δ_{2} | = static deflection, (in, m) at W_{2} if shaft is horizontal |
E | = modulus of elasticity (young's modulus), (psi, N/m^{2}) |
d | = diameter of shaft, (inches, m) |
W_{1} | = load applied to shaft, (lbs, Kg) |
I | = Area Moment of Inertia , (in^{4}, m^{4}) |
l | = distance between centers of bearings, (inches, m) |
a | = distance from bearings to load, (inches, m) |
b | = distance from bearings to load, (inches, m) |
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