A design value used to evaluate the relative stiffness of a pump shaft in a single-stage centrifugal pump with an overhung impeller. The ratio is the length of the shaft cubed (L3) divided by the shaft diameter to the fourth power (D4). The slenderness ratio should fall below 60 when using inches and below 2.0 when using millimeters to avoid excessive shaft bending and deflection. Slenderness ratio is another name for the L3/D4 ratio as applied to single-stage centrifugal pumps with an overhung impeller.
Also known as Stiffness Ratio.