Mechanical Engineering - Torsion- Shafts

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Torsion- Shafts

Why do we use solid shafts for transfer of power in case of pumps/ turbines & other machines why we use a hollow shaft (pipe) in universal joints of automobiles; although the rated load and twist is approx. the same.

Total Answers and Comments: 5

Last Update: August 07, 2009 Asked by: prasanth77

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Best Rated Answer

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Submitted by: devangmehta

In pumps & turbine applications shaft rotates at constant speed except during starting.
While in case of automobile speed & torque changes continuously . Hollow shaft can withstand this good as compare to solid shaft.

Above answer was rated as good by the following members:
bhalchandra123

February 08, 2009 09:34:15

devangmehta

Member Since: February 2009 Contribution: 1

RE: Torsion- Shafts

In pumps & turbine applications shaft rotates at constant speed except during starting.
While in case of automobile speed & torque changes continuously . Hollow shaft can withstand this good as compare to solid shaft.

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1 0

Overall Rating: +1

February 28, 2009 00:51:14

arsalan64

Member Since: January 2009 Contribution: 5

RE: Torsion- Shafts

Solid shafts bear stresses only on its periphery. Where as in hallow shafts stress occur on the periphery as well as the inner surface. So deformation can easily occur in hallow shafts as compared to solid shafts. Solid shafts has high density and can withstand the torsional stress. (If my answer is wrong kindly correct me)

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June 25, 2009 08:28:30

vrsaikumar

Member Since: November 2008 Contribution: 29

RE: Torsion- Shafts

i think we use hollow shafts instead of solid shafts because it is lighter in weight and reduces the bending moment in automobiles....
as all know both the shafts have equal rated load... so why not use hollow shafts and the cost and material can also be saved by using hollow shafts..

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July 26, 2009 04:31:52

kanthasami

Member Since: July 2009 Contribution: 7

RE: Torsion- Shafts

This question can be answered analytically.
We know the Torson Equation

T t
--- ---
J r
J
From this the Section Modulus ---
t
Section modulus of the hollow shaft may be more than that of solid shaft in the case of automobiles. And the Section Modulus of the solid shaft may be more than that of hollow shaft in the case of pumps turbine etc.

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August 07, 2009 12:37:18

akash.2929

Member Since: August 2009 Contribution: 8

RE: Torsion- Shafts

The rated load and twist cannot be same. Had it been same the hollow shaft would have failed. Provided that they have different loads hollow shafts are used for lower loads and twist and they are made hollow for cost control. Please check your question again.

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