Critical Speeds of Rotating Shafts with Single Loads Equations and Calculators
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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|Two Concentrated Loads General Equation *
|N1||= first critical speed, RPM|
|N2||= second critical speed, RPM|
|Δ1||= static deflection, (in, m) at W1 if shaft is horizontal|
|Δ2||= static deflection, (in, m) at W2 if shaft is horizontal|
|E||= modulus of elasticity (young's modulus), (psi, N/m2)|
|d||= diameter of shaft, (inches, m)|
|W1||= load applied to shaft, (lbs, Kg)|
|I||= Area Moment of Inertia , (in4, m4)|
|l||= distance between centers of bearings, (inches, m)|
|a||= distance from bearings to load, (inches, m)|
|b||= distance from bearings to load, (inches, m)|