Question

this questions is wrong? how did come 26here ?

Metal Casting Processes in A true centrifugal casting operation is to be performed horizontally to make copper tube sections with OD = 25 cm and ID = 22.5 cm. What rotational speed is required if a G- factor of 65 is used to cast the tubing? Solution: The inside diameter of the mold D=OD of the casting = 25 cm=0.25 m. We can compute the required rotational speed from Eq. (11.5) as follows: 30 N = 2(9.8)(26) 2 = 61.7 rev/min. V 0.25 In vertical centrifugal casting, the effect of gravity acting on the liquid metal causes the casting wall to be thicker at the base than at the top. The inside profile of the casting wall takes on a parabolic shape. The difference in inside radius between top and bottom is related to speed cf rotation as follows: 30 2gL VR? - R (11.6) -

Answer 1

Yes, it's an error. There must be 65 in place of 26. Because the formula for rotational speed are

N = (30/π) √(2gGF/D)

Where GF is the G-factor and it's given value is 65 not 26.