×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Shaft design

Shaft design

Shaft design

(OP)
Hi,

I need the help on calculating the maximum rotating mass on shaft.
Suppose I have a shaft of .5 inches diameter and Torque is 20lbf-in. How to calculate the maximum weight this shaft can rotate using given torque.

Thanks

Bambila
Mechanical Engineer

RE: Shaft design

If the maximum torque delivered to the shaft is T, then the only limitation on the weight might be.
1)the time needed to come up to speed
2) the braking torque, if greater than T
3) the startup torque of the prime mover (could be as much as 5 times the nominal)
In any event, you get the torsional stress
stress=TR/J
T= maximum torque delivered either by prime mover or braking
R= radius of shaft
J=polar moment of inertia


RE: Shaft design

The question is not bounded very well.

Does the 0.5 inch shaft support the weight, or merely connect to an independently supported object with this amount of weight?
What is the geometry of the object which connects to the shaft?
How is the object attached to the shaft, i.e. welded, bolted, verbally, etc.?
Does the 0.5 inch shaft have a keyway?
How is the 0.5 inch shaft supported?

RE: Shaft design

(OP)
Hi All,

Thanks for the reply. Here I have attached the image of my problem. I hope this would help.

Thanks

Bambila
Mechanical Engineer

RE: Shaft design

Dear Bambila,

This is not a problem related to weight but to inertia.

If bearing friction is neglected, the momentum equation is like this: Torque = moment of inertia (shaft + disc) * angular acceleration

So the torque you have to apply, in an ideal situation, when the shaft is rotating at costant velocity (whatever its value may be), is ZERO. This is because the torque is needed to accelerate the shaft till it reaches full speed. The only thing you have to know is the acceleration needed to reach that speed. Since torque is known, you can easily calculate inertia and then the disk thickness.

The problem is obviously more complicated if a braking torque is needed to keep the shaft at costant velocity.

Regards,

Stefano

RE: Shaft design

The inertia of the rotating weight is to be based on the type of load you are expectings to handle. So you you describe the purpose of the rotating shaft. If you research ME handbooks on for example flywheels integral to mechanical presses, you'll have a good idea how to figure out the size of the rotating mass to maintain the rotational energy that such press require.

RE: Shaft design

OOps"...handle. So you you describe the purpose of the rotating shaft..." I meant to say "...handle. So you should describe the purpose of the rotating shaft..."

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources