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Drive Shaft stress

  1. Aug 12, 2017 #1
    Long drive shaft of 5 inches fits into the end fitting and is rigidly attached by the bolts. Input torque is equal to output torque as we are ignoring losses from bearing. Lets assume that the load on the shaft is equal to 3*weight. (3 g's)

    (looking for more conceptual understanding rather that number crunching)

    has maximum torque of lets say 1000 in-lb. with a use of material that provides max allowable stress of 10000 psi.

    How would we go about drawing the deflection diagram of hallow tube?
    What size bolts would be needing with same stress requirement if there were 6 bolts present?


    What I have so far:
    upload_2017-8-12_20-41-38.png

    where D comes out to be 0.7985 inches. realistically speaking isn't this number is too small?

    Wouldn't the the load and length affect it's diameter?

    Will there is any problem if we were to create hallow shaft using equation below? But not sure what to use for first diameter. How would I draw deflection of hallow shaft?
    upload_2017-8-12_20-40-57.png
     

    Attached Files:

    Last edited: Aug 12, 2017
  2. jcsd
  3. Aug 18, 2017 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
     
  4. Aug 19, 2017 #3

    JBA

    User Avatar

    First, for torsional stress, the τ allowable is the maximum allowable shear stress of the material not its maximum allowable yield stress. As a general rule, the value used for maximum shear stress is 0.57 x the maximum yield stress.

    The deflection of the shaft is in degrees of twisting rotation from one end of the shaft to the other (or in degrees per unit length) and is proportional to the length of the shaft but has no effect on the amount of torque stress on the shaft or a tube. The size of the bolts depends upon the bolt circle diameter on the flange on the end of the shaft.

    As for "drawing the deflection" that is not really applicable for torsional deflection.

    For a tubular shaft the do is the outside diameter of the tube and the di is the inside diameter of the tube.
     
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