# Hollow Shaft vs Solid Shaft- Which Is Better?

Before Selection of Shaft you must considered whether to choose hollow shaft or Solid Shaft depending upon type of application , power Requirement, torque transmission requirement , weight, Cost , machining time , Material .

Difference /Comparison Between Hollow Shaft and Solid shaft as Below:

•  Weight: In comparison to a solid shaft, a hollow shaft is of less weight, for a given length and diameter. This is pretty obvious and wont be requiring any further explanation. Moreover it’s a good idea to go ahead with hollow shafts, if we our emphasis is on weight reduction and cost-cutting.
• Hollow shafts are much better to take torsional loads compared to solid shafts. As shown in the figure, shear stress in a “shaft subjected to torsion” varies linearly from zero at the center to the maximum at the boundary. Inside a solid shaft, most of the material experiences / carries a shear stress whose value is much below the maximum shear stress [Interior portion of the shaft]. But at the same they are adding to the weight, without contributing much to the capability of the shaft to carry torsional load.
Shear stress at a point in a hollow shaft (τ)(τ) is given by , τ=TrIpτ=TrIp

where τ=τ=Shear stress in a hollow shaft

TT = Torque in shaft (N-m)

rr = radial distance from the center to the point of interest (m)

Ip=Ip=Polar area moment of inertia (m4m4)

Average shear stress[ (Min. Shear stress + Max. Shear Stress))/ 2 ] in a hollow shaft will be higher compared to a solid shaft and it’s value is more closer to the maximum shear stress.
Hollow shaft has a greater Strength to weight ratio.

• Wall Thickness: If we reduce the wall thickness, then there are chances of wrinkling or buckling of the shaft wall. So we have to be careful about these things.
• Cost Consideration :  Cost of Hollow shaft is more than solid shaft because of machining is needed for hollow shaft which is time consuming .
• Hollow shaft exhibits high resistance to stresses while the solid shaft may tend to fracture at a certain limit.

Selection Of Hollow Shaft or Solid Shaft Depends On :

For a load bearing type of shaft, then its always better to choose hollow shaft because it has higher stiffness and rigidity and can resist slightly higher bending moments.

A shaft for torque transmission like crank shafts, drive shafts it is always better to choose a solid shaft because it has higher torsional stiffness.

Hollow shaft is not always better compare to a solid shaft. It depends on our uses.When there is no space constraint, then for same mass, hollow shaft is better than solid shaft. But if we have radial space constraint then solid shaft is preferred since, in this case solid shaft has more power transfer capacity than hollow shaft.

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