Determine maximum internal diameter of hollow shaft:
A solid shaft of mild steel which is 200 mm in diameter is to be replaced by hollow shaft of alloy steel for which the allowable shear stress is 22 percent greater. If power which is to be transmitted is to be increased by 20 percent and the speed of rotation increased by 6 percent, determine maximum internal diameter of hollow shaft. The external diameter of hollow shaft is to be 200 mm.
Sol.: Solid shaft diameter d = 200mm
Outer diameter of Hollow shaft = do = 200mm
Inner diameter of Hollow shaft = di = ?
Allowable shear stress τ H = 1.22 S
Power transmitted PH = 1.20PS
Shaft speed NH = 1.06NS
Now use PH = 1.20PS
2 .NHTH/60 = 1.2 [2 .NSTS/60]
NHTH = 1.2 NSTS
As NH = 1.06NS, putting this values