A 50 m long propeller solid shaft for a ship has been designed for a low-carbon steel that has an allowable shear stress of 80 MPa. To safely carry the design torque with the low-carbon steel requires a solid shaft that has an outside diameter of 325 mm.
It has been decided to change the design from a solid shaft to a hollow shaft made of a stronger alloy steel that has an allowable shear stress of 150 MPa. The 325 mm outside diameter is to be retained in the redesigned hollow propeller shaft.
Determine the maximum allowable inside diameter (rounded down to the nearest millimeter) that can be used for the redesigned hollow propeller shaft made of alloy steel.